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--- a/LICENSE.md
+++ b/LICENSE.md
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 Tendermint P2P
 Copyright (C) 2015 Tendermint

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.

 //--------------------------------------------------------------------------------

 GNU GENERAL PUBLIC LICENSE

 Version 3, 29 June 2007

 Copyright © 2007 Free Software Foundation, Inc. <http://fsf.org/>

 Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

 Preamble

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 The licenses for most software and other practical works are designed to take away your freedom to share and change the works. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change all versions of a program--to make sure it remains free software for all its users. We, the Free Software Foundation, use the GNU General Public License for most of our software; it applies also to any other work released this way by its authors. You can apply it to your programs, too.

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 The precise terms and conditions for copying, distribution and modification follow.

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 END OF TERMS AND CONDITIONS
--- a/README.md
+++ b/README.md
@ -0,0 +1,77 @@
 # `tendermint/go-p2p`

 `tendermint/go-p2p` provides an abstraction around peer-to-peer communication.<br/>

 ## Peer/MConnection/Channel

 Each peer has one `MConnection` (multiplex connection) instance.

 __multiplex__ *noun* a system or signal involving simultaneous transmission of
 several messages along a single channel of communication.

 Each `MConnection` handles message transmission on multiple abstract communication
 `Channel`s.  Each channel has a globally unique byte id.
 The byte id and the relative priorities of each `Channel` are configured upon
 initialization of the connection.

 There are two methods for sending messages:
 ```go
 func (m MConnection) Send(chID byte, msg interface{}) bool {}
 func (m MConnection) TrySend(chID byte, msg interface{}) bool {}
 ```

 `Send(chID, msg)` is a blocking call that waits until `msg` is successfully queued
 for the channel with the given id byte `chID`.  The message `msg` is serialized
 using the `tendermint/wire` submodule's `WriteBinary()` reflection routine.

 `TrySend(chID, msg)` is a nonblocking call that returns false if the channel's
 queue is full.

 `Send()` and `TrySend()` are also exposed for each `Peer`.

 ## Switch/Reactor

 The `Switch` handles peer connections and exposes an API to receive incoming messages
 on `Reactors`.  Each `Reactor` is responsible for handling incoming messages of one
 or more `Channels`.  So while sending outgoing messages is typically performed on the peer,
 incoming messages are received on the reactor.

 ```go
 // Declare a MyReactor reactor that handles messages on MyChannelID.
 type MyReactor struct{}

 func (reactor MyReactor) GetChannels() []*ChannelDescriptor {
    return []*ChannelDescriptor{ChannelDescriptor{ID:MyChannelID, Priority: 1}}
 }

 func (reactor MyReactor) Receive(chID byte, peer *Peer, msgBytes []byte) {
    r, n, err := bytes.NewBuffer(msgBytes), new(int64), new(error)
    msgString := ReadString(r, n, err)
    fmt.Println(msgString)
 }

 // Other Reactor methods omitted for brevity
 ...

 switch := NewSwitch([]Reactor{MyReactor{}})

 ...

 // Send a random message to all outbound connections
 for _, peer := range switch.Peers().List() {
    if peer.IsOutbound() {
        peer.Send(MyChannelID, "Here's a random message")
    }
 }
 ```

 ### PexReactor/AddrBook

 A `PEXReactor` reactor implementation is provided to automate peer discovery.

 ```go
 book := p2p.NewAddrBook(addrBookFilePath)
 pexReactor := p2p.NewPEXReactor(book)
 ...
 switch := NewSwitch([]Reactor{pexReactor, myReactor, ...})
 ```
--- a/addrbook.go
+++ b/addrbook.go
@ -0,0 +1,813 @@
 // Modified for Tendermint
 // Originally Copyright (c) 2013-2014 Conformal Systems LLC.
 // https://github.com/conformal/btcd/blob/master/LICENSE

 package p2p

 import (
 	"encoding/binary"
 	"encoding/json"
 	"math"
 	"math/rand"
 	"net"
 	"os"
 	"sync"
 	"time"

 	. "github.com/tendermint/go-common"
 )

 const (
 	// addresses under which the address manager will claim to need more addresses.
 	needAddressThreshold = 1000

 	// interval used to dump the address cache to disk for future use.
 	dumpAddressInterval = time.Minute * 2

 	// max addresses in each old address bucket.
 	oldBucketSize = 64

 	// buckets we split old addresses over.
 	oldBucketCount = 64

 	// max addresses in each new address bucket.
 	newBucketSize = 64

 	// buckets that we spread new addresses over.
 	newBucketCount = 256

 	// old buckets over which an address group will be spread.
 	oldBucketsPerGroup = 4

 	// new buckets over which an source address group will be spread.
 	newBucketsPerGroup = 32

 	// buckets a frequently seen new address may end up in.
 	maxNewBucketsPerAddress = 4

 	// days before which we assume an address has vanished
 	// if we have not seen it announced in that long.
 	numMissingDays = 30

 	// tries without a single success before we assume an address is bad.
 	numRetries = 3

 	// max failures we will accept without a success before considering an address bad.
 	maxFailures = 10

 	// days since the last success before we will consider evicting an address.
 	minBadDays = 7

 	// % of total addresses known returned by GetSelection.
 	getSelectionPercent = 23

 	// min addresses that must be returned by GetSelection. Useful for bootstrapping.
 	minGetSelection = 32

 	// max addresses returned by GetSelection
 	maxGetSelection = 2500

 	// current version of the on-disk format.
 	serializationVersion = 1
 )

 /* AddrBook - concurrency safe peer address manager */
 type AddrBook struct {
 	QuitService

 	mtx        sync.Mutex
 	filePath   string
 	rand       *rand.Rand
 	key        string
 	ourAddrs   map[string]*NetAddress
 	addrLookup map[string]*knownAddress // new & old
 	addrNew    []map[string]*knownAddress
 	addrOld    []map[string]*knownAddress
 	wg         sync.WaitGroup
 	nOld       int
 	nNew       int
 }

 const (
 	bucketTypeNew = 0x01
 	bucketTypeOld = 0x02
 )

 // Use Start to begin processing asynchronous address updates.
 func NewAddrBook(filePath string) *AddrBook {
 	am := &AddrBook{
 		rand:       rand.New(rand.NewSource(time.Now().UnixNano())),
 		ourAddrs:   make(map[string]*NetAddress),
 		addrLookup: make(map[string]*knownAddress),
 		filePath:   filePath,
 	}
 	am.init()
 	am.QuitService = *NewQuitService(log, "AddrBook", am)
 	return am
 }

 // When modifying this, don't forget to update loadFromFile()
 func (a *AddrBook) init() {
 	a.key = CRandHex(24) // 24/2 * 8 = 96 bits
 	// New addr buckets
 	a.addrNew = make([]map[string]*knownAddress, newBucketCount)
 	for i := range a.addrNew {
 		a.addrNew[i] = make(map[string]*knownAddress)
 	}
 	// Old addr buckets
 	a.addrOld = make([]map[string]*knownAddress, oldBucketCount)
 	for i := range a.addrOld {
 		a.addrOld[i] = make(map[string]*knownAddress)
 	}
 }

 func (a *AddrBook) OnStart() error {
 	a.QuitService.OnStart()
 	a.loadFromFile(a.filePath)
 	a.wg.Add(1)
 	go a.saveRoutine()
 	return nil
 }

 func (a *AddrBook) OnStop() {
 	a.QuitService.OnStop()
 	a.wg.Wait()
 }

 func (a *AddrBook) AddOurAddress(addr *NetAddress) {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()
 	log.Info("Add our address to book", "addr", addr)
 	a.ourAddrs[addr.String()] = addr
 }

 func (a *AddrBook) OurAddresses() []*NetAddress {
 	addrs := []*NetAddress{}
 	for _, addr := range a.ourAddrs {
 		addrs = append(addrs, addr)
 	}
 	return addrs
 }

 func (a *AddrBook) AddAddress(addr *NetAddress, src *NetAddress) {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()
 	log.Info("Add address to book", "addr", addr, "src", src)
 	a.addAddress(addr, src)
 }

 func (a *AddrBook) NeedMoreAddrs() bool {
 	return a.Size() < needAddressThreshold
 }

 func (a *AddrBook) Size() int {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()
 	return a.size()
 }

 func (a *AddrBook) size() int {
 	return a.nNew + a.nOld
 }

 // Pick an address to connect to with new/old bias.
 func (a *AddrBook) PickAddress(newBias int) *NetAddress {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()

 	if a.size() == 0 {
 		return nil
 	}
 	if newBias > 100 {
 		newBias = 100
 	}
 	if newBias < 0 {
 		newBias = 0
 	}

 	// Bias between new and old addresses.
 	oldCorrelation := math.Sqrt(float64(a.nOld)) * (100.0 - float64(newBias))
 	newCorrelation := math.Sqrt(float64(a.nNew)) * float64(newBias)

 	if (newCorrelation+oldCorrelation)*a.rand.Float64() < oldCorrelation {
 		// pick random Old bucket.
 		var bucket map[string]*knownAddress = nil
 		for len(bucket) == 0 {
 			bucket = a.addrOld[a.rand.Intn(len(a.addrOld))]
 		}
 		// pick a random ka from bucket.
 		randIndex := a.rand.Intn(len(bucket))
 		for _, ka := range bucket {
 			if randIndex == 0 {
 				return ka.Addr
 			}
 			randIndex--
 		}
 		PanicSanity("Should not happen")
 	} else {
 		// pick random New bucket.
 		var bucket map[string]*knownAddress = nil
 		for len(bucket) == 0 {
 			bucket = a.addrNew[a.rand.Intn(len(a.addrNew))]
 		}
 		// pick a random ka from bucket.
 		randIndex := a.rand.Intn(len(bucket))
 		for _, ka := range bucket {
 			if randIndex == 0 {
 				return ka.Addr
 			}
 			randIndex--
 		}
 		PanicSanity("Should not happen")
 	}
 	return nil
 }

 func (a *AddrBook) MarkGood(addr *NetAddress) {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()
 	ka := a.addrLookup[addr.String()]
 	if ka == nil {
 		return
 	}
 	ka.markGood()
 	if ka.isNew() {
 		a.moveToOld(ka)
 	}
 }

 func (a *AddrBook) MarkAttempt(addr *NetAddress) {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()
 	ka := a.addrLookup[addr.String()]
 	if ka == nil {
 		return
 	}
 	ka.markAttempt()
 }

 func (a *AddrBook) MarkBad(addr *NetAddress) {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()
 	ka := a.addrLookup[addr.String()]
 	if ka == nil {
 		return
 	}
 	// We currently just eject the address.
 	// In the future, consider blacklisting.
 	a.removeFromAllBuckets(ka)
 }

 /* Peer exchange */

 // GetSelection randomly selects some addresses (old & new). Suitable for peer-exchange protocols.
 func (a *AddrBook) GetSelection() []*NetAddress {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()

 	if a.size() == 0 {
 		return nil
 	}

 	allAddr := make([]*NetAddress, a.size())
 	i := 0
 	for _, v := range a.addrLookup {
 		allAddr[i] = v.Addr
 		i++
 	}

 	numAddresses := MaxInt(
 		MinInt(minGetSelection, len(allAddr)),
 		len(allAddr)*getSelectionPercent/100)
 	numAddresses = MinInt(maxGetSelection, numAddresses)

 	// Fisher-Yates shuffle the array. We only need to do the first
 	// `numAddresses' since we are throwing the rest.
 	for i := 0; i < numAddresses; i++ {
 		// pick a number between current index and the end
 		j := rand.Intn(len(allAddr)-i) + i
 		allAddr[i], allAddr[j] = allAddr[j], allAddr[i]
 	}

 	// slice off the limit we are willing to share.
 	return allAddr[:numAddresses]
 }

 /* Loading & Saving */

 type addrBookJSON struct {
 	Key   string
 	Addrs []*knownAddress
 }

 func (a *AddrBook) saveToFile(filePath string) {
 	// Compile Addrs
 	addrs := []*knownAddress{}
 	for _, ka := range a.addrLookup {
 		addrs = append(addrs, ka)
 	}

 	aJSON := &addrBookJSON{
 		Key:   a.key,
 		Addrs: addrs,
 	}

 	jsonBytes, err := json.MarshalIndent(aJSON, "", "\t")
 	if err != nil {
 		log.Error("Failed to save AddrBook to file", "err", err)
 		return
 	}
 	err = WriteFileAtomic(filePath, jsonBytes)
 	if err != nil {
 		log.Error("Failed to save AddrBook to file", "file", filePath, "error", err)
 	}
 }

 // Returns false if file does not exist.
 // Panics if file is corrupt.
 func (a *AddrBook) loadFromFile(filePath string) bool {
 	// If doesn't exist, do nothing.
 	_, err := os.Stat(filePath)
 	if os.IsNotExist(err) {
 		return false
 	}

 	// Load addrBookJSON{}
 	r, err := os.Open(filePath)
 	if err != nil {
 		PanicCrisis(Fmt("Error opening file %s: %v", filePath, err))
 	}
 	defer r.Close()
 	aJSON := &addrBookJSON{}
 	dec := json.NewDecoder(r)
 	err = dec.Decode(aJSON)
 	if err != nil {
 		PanicCrisis(Fmt("Error reading file %s: %v", filePath, err))
 	}

 	// Restore all the fields...
 	// Restore the key
 	a.key = aJSON.Key
 	// Restore .addrNew & .addrOld
 	for _, ka := range aJSON.Addrs {
 		for _, bucketIndex := range ka.Buckets {
 			bucket := a.getBucket(ka.BucketType, bucketIndex)
 			bucket[ka.Addr.String()] = ka
 		}
 		a.addrLookup[ka.Addr.String()] = ka
 		if ka.BucketType == bucketTypeNew {
 			a.nNew++
 		} else {
 			a.nOld++
 		}
 	}
 	return true
 }

 /* Private methods */

 func (a *AddrBook) saveRoutine() {
 	dumpAddressTicker := time.NewTicker(dumpAddressInterval)
 out:
 	for {
 		select {
 		case <-dumpAddressTicker.C:
 			log.Info("Saving AddrBook to file", "size", a.Size())
 			a.saveToFile(a.filePath)
 		case <-a.Quit:
 			break out
 		}
 	}
 	dumpAddressTicker.Stop()
 	a.saveToFile(a.filePath)
 	a.wg.Done()
 	log.Notice("Address handler done")
 }

 func (a *AddrBook) getBucket(bucketType byte, bucketIdx int) map[string]*knownAddress {
 	switch bucketType {
 	case bucketTypeNew:
 		return a.addrNew[bucketIdx]
 	case bucketTypeOld:
 		return a.addrOld[bucketIdx]
 	default:
 		PanicSanity("Should not happen")
 		return nil
 	}
 }

 // Adds ka to new bucket. Returns false if it couldn't do it cuz buckets full.
 // NOTE: currently it always returns true.
 func (a *AddrBook) addToNewBucket(ka *knownAddress, bucketIdx int) bool {
 	// Sanity check
 	if ka.isOld() {
 		log.Warn(Fmt("Cannot add address already in old bucket to a new bucket: %v", ka))
 		return false
 	}

 	addrStr := ka.Addr.String()
 	bucket := a.getBucket(bucketTypeNew, bucketIdx)

 	// Already exists?
 	if _, ok := bucket[addrStr]; ok {
 		return true
 	}

 	// Enforce max addresses.
 	if len(bucket) > newBucketSize {
 		log.Notice("new bucket is full, expiring old ")
 		a.expireNew(bucketIdx)
 	}

 	// Add to bucket.
 	bucket[addrStr] = ka
 	if ka.addBucketRef(bucketIdx) == 1 {
 		a.nNew++
 	}

 	// Ensure in addrLookup
 	a.addrLookup[addrStr] = ka

 	return true
 }

 // Adds ka to old bucket. Returns false if it couldn't do it cuz buckets full.
 func (a *AddrBook) addToOldBucket(ka *knownAddress, bucketIdx int) bool {
 	// Sanity check
 	if ka.isNew() {
 		log.Warn(Fmt("Cannot add new address to old bucket: %v", ka))
 		return false
 	}
 	if len(ka.Buckets) != 0 {
 		log.Warn(Fmt("Cannot add already old address to another old bucket: %v", ka))
 		return false
 	}

 	addrStr := ka.Addr.String()
 	bucket := a.getBucket(bucketTypeNew, bucketIdx)

 	// Already exists?
 	if _, ok := bucket[addrStr]; ok {
 		return true
 	}

 	// Enforce max addresses.
 	if len(bucket) > oldBucketSize {
 		return false
 	}

 	// Add to bucket.
 	bucket[addrStr] = ka
 	if ka.addBucketRef(bucketIdx) == 1 {
 		a.nOld++
 	}

 	// Ensure in addrLookup
 	a.addrLookup[addrStr] = ka

 	return true
 }

 func (a *AddrBook) removeFromBucket(ka *knownAddress, bucketType byte, bucketIdx int) {
 	if ka.BucketType != bucketType {
 		log.Warn(Fmt("Bucket type mismatch: %v", ka))
 		return
 	}
 	bucket := a.getBucket(bucketType, bucketIdx)
 	delete(bucket, ka.Addr.String())
 	if ka.removeBucketRef(bucketIdx) == 0 {
 		if bucketType == bucketTypeNew {
 			a.nNew--
 		} else {
 			a.nOld--
 		}
 		delete(a.addrLookup, ka.Addr.String())
 	}
 }

 func (a *AddrBook) removeFromAllBuckets(ka *knownAddress) {
 	for _, bucketIdx := range ka.Buckets {
 		bucket := a.getBucket(ka.BucketType, bucketIdx)
 		delete(bucket, ka.Addr.String())
 	}
 	ka.Buckets = nil
 	if ka.BucketType == bucketTypeNew {
 		a.nNew--
 	} else {
 		a.nOld--
 	}
 	delete(a.addrLookup, ka.Addr.String())
 }

 func (a *AddrBook) pickOldest(bucketType byte, bucketIdx int) *knownAddress {
 	bucket := a.getBucket(bucketType, bucketIdx)
 	var oldest *knownAddress
 	for _, ka := range bucket {
 		if oldest == nil || ka.LastAttempt.Before(oldest.LastAttempt) {
 			oldest = ka
 		}
 	}
 	return oldest
 }

 func (a *AddrBook) addAddress(addr, src *NetAddress) {
 	if !addr.Routable() {
 		log.Warn(Fmt("Cannot add non-routable address %v", addr))
 		return
 	}
 	if _, ok := a.ourAddrs[addr.String()]; ok {
 		// Ignore our own listener address.
 		return
 	}

 	ka := a.addrLookup[addr.String()]

 	if ka != nil {
 		// Already old.
 		if ka.isOld() {
 			return
 		}
 		// Already in max new buckets.
 		if len(ka.Buckets) == maxNewBucketsPerAddress {
 			return
 		}
 		// The more entries we have, the less likely we are to add more.
 		factor := int32(2 * len(ka.Buckets))
 		if a.rand.Int31n(factor) != 0 {
 			return
 		}
 	} else {
 		ka = newKnownAddress(addr, src)
 	}

 	bucket := a.calcNewBucket(addr, src)
 	a.addToNewBucket(ka, bucket)

 	log.Notice("Added new address", "address", addr, "total", a.size())
 }

 // Make space in the new buckets by expiring the really bad entries.
 // If no bad entries are available we remove the oldest.
 func (a *AddrBook) expireNew(bucketIdx int) {
 	for addrStr, ka := range a.addrNew[bucketIdx] {
 		// If an entry is bad, throw it away
 		if ka.isBad() {
 			log.Notice(Fmt("expiring bad address %v", addrStr))
 			a.removeFromBucket(ka, bucketTypeNew, bucketIdx)
 			return
 		}
 	}

 	// If we haven't thrown out a bad entry, throw out the oldest entry
 	oldest := a.pickOldest(bucketTypeNew, bucketIdx)
 	a.removeFromBucket(oldest, bucketTypeNew, bucketIdx)
 }

 // Promotes an address from new to old.
 // TODO: Move to old probabilistically.
 // The better a node is, the less likely it should be evicted from an old bucket.
 func (a *AddrBook) moveToOld(ka *knownAddress) {
 	// Sanity check
 	if ka.isOld() {
 		log.Warn(Fmt("Cannot promote address that is already old %v", ka))
 		return
 	}
 	if len(ka.Buckets) == 0 {
 		log.Warn(Fmt("Cannot promote address that isn't in any new buckets %v", ka))
 		return
 	}

 	// Remember one of the buckets in which ka is in.
 	freedBucket := ka.Buckets[0]
 	// Remove from all (new) buckets.
 	a.removeFromAllBuckets(ka)
 	// It's officially old now.
 	ka.BucketType = bucketTypeOld

 	// Try to add it to its oldBucket destination.
 	oldBucketIdx := a.calcOldBucket(ka.Addr)
 	added := a.addToOldBucket(ka, oldBucketIdx)
 	if !added {
 		// No room, must evict something
 		oldest := a.pickOldest(bucketTypeOld, oldBucketIdx)
 		a.removeFromBucket(oldest, bucketTypeOld, oldBucketIdx)
 		// Find new bucket to put oldest in
 		newBucketIdx := a.calcNewBucket(oldest.Addr, oldest.Src)
 		added := a.addToNewBucket(oldest, newBucketIdx)
 		// No space in newBucket either, just put it in freedBucket from above.
 		if !added {
 			added := a.addToNewBucket(oldest, freedBucket)
 			if !added {
 				log.Warn(Fmt("Could not migrate oldest %v to freedBucket %v", oldest, freedBucket))
 			}
 		}
 		// Finally, add to bucket again.
 		added = a.addToOldBucket(ka, oldBucketIdx)
 		if !added {
 			log.Warn(Fmt("Could not re-add ka %v to oldBucketIdx %v", ka, oldBucketIdx))
 		}
 	}
 }

 // doublesha256(  key + sourcegroup +
 //                int64(doublesha256(key + group + sourcegroup))%bucket_per_group  ) % num_new_buckets
 func (a *AddrBook) calcNewBucket(addr, src *NetAddress) int {
 	data1 := []byte{}
 	data1 = append(data1, []byte(a.key)...)
 	data1 = append(data1, []byte(groupKey(addr))...)
 	data1 = append(data1, []byte(groupKey(src))...)
 	hash1 := doubleSha256(data1)
 	hash64 := binary.BigEndian.Uint64(hash1)
 	hash64 %= newBucketsPerGroup
 	var hashbuf [8]byte
 	binary.BigEndian.PutUint64(hashbuf[:], hash64)
 	data2 := []byte{}
 	data2 = append(data2, []byte(a.key)...)
 	data2 = append(data2, groupKey(src)...)
 	data2 = append(data2, hashbuf[:]...)

 	hash2 := doubleSha256(data2)
 	return int(binary.BigEndian.Uint64(hash2) % newBucketCount)
 }

 // doublesha256(  key + group +
 //                int64(doublesha256(key + addr))%buckets_per_group  ) % num_old_buckets
 func (a *AddrBook) calcOldBucket(addr *NetAddress) int {
 	data1 := []byte{}
 	data1 = append(data1, []byte(a.key)...)
 	data1 = append(data1, []byte(addr.String())...)
 	hash1 := doubleSha256(data1)
 	hash64 := binary.BigEndian.Uint64(hash1)
 	hash64 %= oldBucketsPerGroup
 	var hashbuf [8]byte
 	binary.BigEndian.PutUint64(hashbuf[:], hash64)
 	data2 := []byte{}
 	data2 = append(data2, []byte(a.key)...)
 	data2 = append(data2, groupKey(addr)...)
 	data2 = append(data2, hashbuf[:]...)

 	hash2 := doubleSha256(data2)
 	return int(binary.BigEndian.Uint64(hash2) % oldBucketCount)
 }

 // Return a string representing the network group of this address.
 // This is the /16 for IPv6, the /32 (/36 for he.net) for IPv6, the string
 // "local" for a local address and the string "unroutable for an unroutable
 // address.
 func groupKey(na *NetAddress) string {
 	if na.Local() {
 		return "local"
 	}
 	if !na.Routable() {
 		return "unroutable"
 	}

 	if ipv4 := na.IP.To4(); ipv4 != nil {
 		return (&net.IPNet{IP: na.IP, Mask: net.CIDRMask(16, 32)}).String()
 	}
 	if na.RFC6145() || na.RFC6052() {
 		// last four bytes are the ip address
 		ip := net.IP(na.IP[12:16])
 		return (&net.IPNet{IP: ip, Mask: net.CIDRMask(16, 32)}).String()
 	}

 	if na.RFC3964() {
 		ip := net.IP(na.IP[2:7])
 		return (&net.IPNet{IP: ip, Mask: net.CIDRMask(16, 32)}).String()

 	}
 	if na.RFC4380() {
 		// teredo tunnels have the last 4 bytes as the v4 address XOR
 		// 0xff.
 		ip := net.IP(make([]byte, 4))
 		for i, byte := range na.IP[12:16] {
 			ip[i] = byte ^ 0xff
 		}
 		return (&net.IPNet{IP: ip, Mask: net.CIDRMask(16, 32)}).String()
 	}

 	// OK, so now we know ourselves to be a IPv6 address.
 	// bitcoind uses /32 for everything, except for Hurricane Electric's
 	// (he.net) IP range, which it uses /36 for.
 	bits := 32
 	heNet := &net.IPNet{IP: net.ParseIP("2001:470::"),
 		Mask: net.CIDRMask(32, 128)}
 	if heNet.Contains(na.IP) {
 		bits = 36
 	}

 	return (&net.IPNet{IP: na.IP, Mask: net.CIDRMask(bits, 128)}).String()
 }

 //-----------------------------------------------------------------------------

 /*
   knownAddress

   tracks information about a known network address that is used
   to determine how viable an address is.
 */
 type knownAddress struct {
 	Addr        *NetAddress
 	Src         *NetAddress
 	Attempts    int32
 	LastAttempt time.Time
 	LastSuccess time.Time
 	BucketType  byte
 	Buckets     []int
 }

 func newKnownAddress(addr *NetAddress, src *NetAddress) *knownAddress {
 	return &knownAddress{
 		Addr:        addr,
 		Src:         src,
 		Attempts:    0,
 		LastAttempt: time.Now(),
 		BucketType:  bucketTypeNew,
 		Buckets:     nil,
 	}
 }

 func (ka *knownAddress) isOld() bool {
 	return ka.BucketType == bucketTypeOld
 }

 func (ka *knownAddress) isNew() bool {
 	return ka.BucketType == bucketTypeNew
 }

 func (ka *knownAddress) markAttempt() {
 	now := time.Now()
 	ka.LastAttempt = now
 	ka.Attempts += 1
 }

 func (ka *knownAddress) markGood() {
 	now := time.Now()
 	ka.LastAttempt = now
 	ka.Attempts = 0
 	ka.LastSuccess = now
 }

 func (ka *knownAddress) addBucketRef(bucketIdx int) int {
 	for _, bucket := range ka.Buckets {
 		if bucket == bucketIdx {
 			log.Warn(Fmt("Bucket already exists in ka.Buckets: %v", ka))
 			return -1
 		}
 	}
 	ka.Buckets = append(ka.Buckets, bucketIdx)
 	return len(ka.Buckets)
 }

 func (ka *knownAddress) removeBucketRef(bucketIdx int) int {
 	buckets := []int{}
 	for _, bucket := range ka.Buckets {
 		if bucket != bucketIdx {
 			buckets = append(buckets, bucket)
 		}
 	}
 	if len(buckets) != len(ka.Buckets)-1 {
 		log.Warn(Fmt("bucketIdx not found in ka.Buckets: %v", ka))
 		return -1
 	}
 	ka.Buckets = buckets
 	return len(ka.Buckets)
 }

 /*
   An address is bad if the address in question has not been tried in the last
   minute and meets one of the following criteria:

   1) It claims to be from the future
   2) It hasn't been seen in over a month
   3) It has failed at least three times and never succeeded
   4) It has failed ten times in the last week

   All addresses that meet these criteria are assumed to be worthless and not
   worth keeping hold of.
 */
 func (ka *knownAddress) isBad() bool {
 	// Has been attempted in the last minute --> good
 	if ka.LastAttempt.Before(time.Now().Add(-1 * time.Minute)) {
 		return false
 	}

 	// Over a month old?
 	if ka.LastAttempt.After(time.Now().Add(-1 * numMissingDays * time.Hour * 24)) {
 		return true
 	}

 	// Never succeeded?
 	if ka.LastSuccess.IsZero() && ka.Attempts >= numRetries {
 		return true
 	}

 	// Hasn't succeeded in too long?
 	if ka.LastSuccess.Before(time.Now().Add(-1*minBadDays*time.Hour*24)) &&
 		ka.Attempts >= maxFailures {
 		return true
 	}

 	return false
 }
--- a/addrbook_test.go
+++ b/addrbook_test.go
@ -0,0 +1,161 @@
 package p2p

 import (
 	"fmt"
 	"io/ioutil"
 	"math/rand"
 	"testing"
 )

 func createTempFileName(prefix string) string {
 	f, err := ioutil.TempFile("", prefix)
 	if err != nil {
 		panic(err)
 	}
 	fname := f.Name()
 	err = f.Close()
 	if err != nil {
 		panic(err)
 	}
 	return fname
 }

 func TestEmpty(t *testing.T) {
 	fname := createTempFileName("addrbook_test")
 	// t.Logf("New tempfile name: %v", fname)

 	// Save an empty book & load it
 	book := NewAddrBook(fname)
 	book.saveToFile(fname)

 	book = NewAddrBook(fname)
 	book.loadFromFile(fname)

 	if book.Size() != 0 {
 		t.Errorf("Expected 0 addresses, found %v", book.Size())
 	}
 }

 func randIPv4Address() *NetAddress {
 	for {
 		ip := fmt.Sprintf("%v.%v.%v.%v",
 			rand.Intn(254)+1,
 			rand.Intn(255),
 			rand.Intn(255),
 			rand.Intn(255),
 		)
 		port := rand.Intn(65535-1) + 1
 		addr := NewNetAddressString(fmt.Sprintf("%v:%v", ip, port))
 		if addr.Routable() {
 			return addr
 		}
 	}
 }

 func TestSaveAddresses(t *testing.T) {
 	fname := createTempFileName("addrbook_test")
 	//t.Logf("New tempfile name: %v", fname)

 	// Create some random addresses
 	randAddrs := []struct {
 		addr *NetAddress
 		src  *NetAddress
 	}{}
 	for i := 0; i < 100; i++ {
 		addr := randIPv4Address()
 		src := randIPv4Address()
 		randAddrs = append(randAddrs, struct {
 			addr *NetAddress
 			src  *NetAddress
 		}{
 			addr: addr,
 			src:  src,
 		})
 	}

 	// Create the book & populate & save
 	book := NewAddrBook(fname)
 	for _, addrSrc := range randAddrs {
 		book.AddAddress(addrSrc.addr, addrSrc.src)
 	}
 	if book.Size() != 100 {
 		t.Errorf("Expected 100 addresses, found %v", book.Size())
 	}
 	book.saveToFile(fname)

 	// Reload the book
 	book = NewAddrBook(fname)
 	book.loadFromFile(fname)

 	// Test ...

 	if book.Size() != 100 {
 		t.Errorf("Expected 100 addresses, found %v", book.Size())
 	}

 	for _, addrSrc := range randAddrs {
 		addr := addrSrc.addr
 		src := addrSrc.src
 		ka := book.addrLookup[addr.String()]
 		if ka == nil {
 			t.Fatalf("Expected to find KnownAddress %v but wasn't there.", addr)
 		}
 		if !(ka.Addr.Equals(addr) && ka.Src.Equals(src)) {
 			t.Fatalf("KnownAddress doesn't match addr & src")
 		}
 	}
 }

 func TestPromoteToOld(t *testing.T) {
 	fname := createTempFileName("addrbook_test")
 	t.Logf("New tempfile name: %v", fname)

 	// Create some random addresses
 	randAddrs := []struct {
 		addr *NetAddress
 		src  *NetAddress
 	}{}
 	for i := 0; i < 100; i++ {
 		addr := randIPv4Address()
 		src := randIPv4Address()
 		randAddrs = append(randAddrs, struct {
 			addr *NetAddress
 			src  *NetAddress
 		}{
 			addr: addr,
 			src:  src,
 		})
 	}

 	// Create the book & populate & save
 	book := NewAddrBook(fname)
 	for _, addrSrc := range randAddrs {
 		book.AddAddress(addrSrc.addr, addrSrc.src)
 	}
 	// Attempt all addresses.
 	for _, addrSrc := range randAddrs {
 		book.MarkAttempt(addrSrc.addr)
 	}
 	// Promote half of them
 	for i, addrSrc := range randAddrs {
 		if i%2 == 0 {
 			book.MarkGood(addrSrc.addr)
 		}
 	}
 	book.saveToFile(fname)

 	// Reload the book
 	book = NewAddrBook(fname)
 	book.loadFromFile(fname)

 	// Test ...

 	if book.Size() != 100 {
 		t.Errorf("Expected 100 addresses, found %v", book.Size())
 	}

 	// TODO: do more testing :)

 	selection := book.GetSelection()
 	t.Logf("selection: %v", selection)
 }
--- a/connection.go
+++ b/connection.go
@ -0,0 +1,640 @@
 package p2p

 import (
 	"bufio"
 	"fmt"
 	"io"
 	"math"
 	"net"
 	"runtime/debug"
 	"sync/atomic"
 	"time"

 	flow "github.com/tendermint/flowcontrol"
 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-wire" //"github.com/tendermint/log15"
 )

 const (
 	numBatchMsgPackets        = 10
 	minReadBufferSize         = 1024
 	minWriteBufferSize        = 1024
 	idleTimeoutMinutes        = 5
 	updateStatsSeconds        = 2
 	pingTimeoutSeconds        = 40
 	defaultSendRate           = 51200 // 50Kb/s
 	defaultRecvRate           = 51200 // 50Kb/s
 	flushThrottleMS           = 100
 	defaultSendQueueCapacity  = 1
 	defaultRecvBufferCapacity = 4096
 	defaultSendTimeoutSeconds = 10
 )

 type receiveCbFunc func(chID byte, msgBytes []byte)
 type errorCbFunc func(interface{})

 /*
 Each peer has one `MConnection` (multiplex connection) instance.

 __multiplex__ *noun* a system or signal involving simultaneous transmission of
 several messages along a single channel of communication.

 Each `MConnection` handles message transmission on multiple abstract communication
 `Channel`s.  Each channel has a globally unique byte id.
 The byte id and the relative priorities of each `Channel` are configured upon
 initialization of the connection.

 There are two methods for sending messages:
 	func (m MConnection) Send(chID byte, msg interface{}) bool {}
 	func (m MConnection) TrySend(chID byte, msg interface{}) bool {}

 `Send(chID, msg)` is a blocking call that waits until `msg` is successfully queued
 for the channel with the given id byte `chID`, or until the request times out.
 The message `msg` is serialized using the `tendermint/wire` submodule's
 `WriteBinary()` reflection routine.

 `TrySend(chID, msg)` is a nonblocking call that returns false if the channel's
 queue is full.

 Inbound message bytes are handled with an onReceive callback function.
 */
 type MConnection struct {
 	BaseService

 	conn        net.Conn
 	bufReader   *bufio.Reader
 	bufWriter   *bufio.Writer
 	sendMonitor *flow.Monitor
 	recvMonitor *flow.Monitor
 	sendRate    int64
 	recvRate    int64
 	send        chan struct{}
 	pong        chan struct{}
 	channels    []*Channel
 	channelsIdx map[byte]*Channel
 	onReceive   receiveCbFunc
 	onError     errorCbFunc
 	errored     uint32

 	quit         chan struct{}
 	flushTimer   *ThrottleTimer // flush writes as necessary but throttled.
 	pingTimer    *RepeatTimer   // send pings periodically
 	chStatsTimer *RepeatTimer   // update channel stats periodically

 	LocalAddress  *NetAddress
 	RemoteAddress *NetAddress
 }

 func NewMConnection(conn net.Conn, chDescs []*ChannelDescriptor, onReceive receiveCbFunc, onError errorCbFunc) *MConnection {

 	mconn := &MConnection{
 		conn:        conn,
 		bufReader:   bufio.NewReaderSize(conn, minReadBufferSize),
 		bufWriter:   bufio.NewWriterSize(conn, minWriteBufferSize),
 		sendMonitor: flow.New(0, 0),
 		recvMonitor: flow.New(0, 0),
 		sendRate:    defaultSendRate,
 		recvRate:    defaultRecvRate,
 		send:        make(chan struct{}, 1),
 		pong:        make(chan struct{}),
 		onReceive:   onReceive,
 		onError:     onError,

 		// Initialized in Start()
 		quit:         nil,
 		flushTimer:   nil,
 		pingTimer:    nil,
 		chStatsTimer: nil,

 		LocalAddress:  NewNetAddress(conn.LocalAddr()),
 		RemoteAddress: NewNetAddress(conn.RemoteAddr()),
 	}

 	// Create channels
 	var channelsIdx = map[byte]*Channel{}
 	var channels = []*Channel{}

 	for _, desc := range chDescs {
 		channel := newChannel(mconn, desc)
 		channelsIdx[channel.id] = channel
 		channels = append(channels, channel)
 	}
 	mconn.channels = channels
 	mconn.channelsIdx = channelsIdx

 	mconn.BaseService = *NewBaseService(log, "MConnection", mconn)

 	return mconn
 }

 func (c *MConnection) OnStart() error {
 	c.BaseService.OnStart()
 	c.quit = make(chan struct{})
 	c.flushTimer = NewThrottleTimer("flush", flushThrottleMS*time.Millisecond)
 	c.pingTimer = NewRepeatTimer("ping", pingTimeoutSeconds*time.Second)
 	c.chStatsTimer = NewRepeatTimer("chStats", updateStatsSeconds*time.Second)
 	go c.sendRoutine()
 	go c.recvRoutine()
 	return nil
 }

 func (c *MConnection) OnStop() {
 	c.BaseService.OnStop()
 	c.flushTimer.Stop()
 	c.pingTimer.Stop()
 	c.chStatsTimer.Stop()
 	if c.quit != nil {
 		close(c.quit)
 	}
 	c.conn.Close()
 	// We can't close pong safely here because
 	// recvRoutine may write to it after we've stopped.
 	// Though it doesn't need to get closed at all,
 	// we close it @ recvRoutine.
 	// close(c.pong)
 }

 func (c *MConnection) String() string {
 	return fmt.Sprintf("MConn{%v}", c.conn.RemoteAddr())
 }

 func (c *MConnection) flush() {
 	log.Debug("Flush", "conn", c)
 	err := c.bufWriter.Flush()
 	if err != nil {
 		log.Warn("MConnection flush failed", "error", err)
 	}
 }

 // Catch panics, usually caused by remote disconnects.
 func (c *MConnection) _recover() {
 	if r := recover(); r != nil {
 		stack := debug.Stack()
 		err := StackError{r, stack}
 		c.stopForError(err)
 	}
 }

 func (c *MConnection) stopForError(r interface{}) {
 	c.Stop()
 	if atomic.CompareAndSwapUint32(&c.errored, 0, 1) {
 		if c.onError != nil {
 			c.onError(r)
 		}
 	}
 }

 // Queues a message to be sent to channel.
 func (c *MConnection) Send(chID byte, msg interface{}) bool {
 	if !c.IsRunning() {
 		return false
 	}

 	log.Info("Send", "channel", chID, "conn", c, "msg", msg) //, "bytes", wire.BinaryBytes(msg))

 	// Send message to channel.
 	channel, ok := c.channelsIdx[chID]
 	if !ok {
 		log.Error(Fmt("Cannot send bytes, unknown channel %X", chID))
 		return false
 	}

 	success := channel.sendBytes(wire.BinaryBytes(msg))
 	if success {
 		// Wake up sendRoutine if necessary
 		select {
 		case c.send <- struct{}{}:
 		default:
 		}
 	} else {
 		log.Warn("Send failed", "channel", chID, "conn", c, "msg", msg)
 	}
 	return success
 }

 // Queues a message to be sent to channel.
 // Nonblocking, returns true if successful.
 func (c *MConnection) TrySend(chID byte, msg interface{}) bool {
 	if !c.IsRunning() {
 		return false
 	}

 	log.Info("TrySend", "channel", chID, "conn", c, "msg", msg)

 	// Send message to channel.
 	channel, ok := c.channelsIdx[chID]
 	if !ok {
 		log.Error(Fmt("Cannot send bytes, unknown channel %X", chID))
 		return false
 	}

 	ok = channel.trySendBytes(wire.BinaryBytes(msg))
 	if ok {
 		// Wake up sendRoutine if necessary
 		select {
 		case c.send <- struct{}{}:
 		default:
 		}
 	}

 	return ok
 }

 func (c *MConnection) CanSend(chID byte) bool {
 	if !c.IsRunning() {
 		return false
 	}

 	channel, ok := c.channelsIdx[chID]
 	if !ok {
 		log.Error(Fmt("Unknown channel %X", chID))
 		return false
 	}
 	return channel.canSend()
 }

 // sendRoutine polls for packets to send from channels.
 func (c *MConnection) sendRoutine() {
 	defer c._recover()

 FOR_LOOP:
 	for {
 		var n int64
 		var err error
 		select {
 		case <-c.flushTimer.Ch:
 			// NOTE: flushTimer.Set() must be called every time
 			// something is written to .bufWriter.
 			c.flush()
 		case <-c.chStatsTimer.Ch:
 			for _, channel := range c.channels {
 				channel.updateStats()
 			}
 		case <-c.pingTimer.Ch:
 			log.Info("Send Ping")
 			wire.WriteByte(packetTypePing, c.bufWriter, &n, &err)
 			c.sendMonitor.Update(int(n))
 			c.flush()
 		case <-c.pong:
 			log.Info("Send Pong")
 			wire.WriteByte(packetTypePong, c.bufWriter, &n, &err)
 			c.sendMonitor.Update(int(n))
 			c.flush()
 		case <-c.quit:
 			break FOR_LOOP
 		case <-c.send:
 			// Send some msgPackets
 			eof := c.sendSomeMsgPackets()
 			if !eof {
 				// Keep sendRoutine awake.
 				select {
 				case c.send <- struct{}{}:
 				default:
 				}
 			}
 		}

 		if !c.IsRunning() {
 			break FOR_LOOP
 		}
 		if err != nil {
 			log.Warn("Connection failed @ sendRoutine", "conn", c, "error", err)
 			c.stopForError(err)
 			break FOR_LOOP
 		}
 	}

 	// Cleanup
 }

 // Returns true if messages from channels were exhausted.
 // Blocks in accordance to .sendMonitor throttling.
 func (c *MConnection) sendSomeMsgPackets() bool {
 	// Block until .sendMonitor says we can write.
 	// Once we're ready we send more than we asked for,
 	// but amortized it should even out.
 	c.sendMonitor.Limit(maxMsgPacketSize, atomic.LoadInt64(&c.sendRate), true)

 	// Now send some msgPackets.
 	for i := 0; i < numBatchMsgPackets; i++ {
 		if c.sendMsgPacket() {
 			return true
 		}
 	}
 	return false
 }

 // Returns true if messages from channels were exhausted.
 func (c *MConnection) sendMsgPacket() bool {
 	// Choose a channel to create a msgPacket from.
 	// The chosen channel will be the one whose recentlySent/priority is the least.
 	var leastRatio float32 = math.MaxFloat32
 	var leastChannel *Channel
 	for _, channel := range c.channels {
 		// If nothing to send, skip this channel
 		if !channel.isSendPending() {
 			continue
 		}
 		// Get ratio, and keep track of lowest ratio.
 		ratio := float32(channel.recentlySent) / float32(channel.priority)
 		if ratio < leastRatio {
 			leastRatio = ratio
 			leastChannel = channel
 		}
 	}

 	// Nothing to send?
 	if leastChannel == nil {
 		return true
 	} else {
 		// log.Info("Found a msgPacket to send")
 	}

 	// Make & send a msgPacket from this channel
 	n, err := leastChannel.writeMsgPacketTo(c.bufWriter)
 	if err != nil {
 		log.Warn("Failed to write msgPacket", "error", err)
 		c.stopForError(err)
 		return true
 	}
 	c.sendMonitor.Update(int(n))
 	c.flushTimer.Set()
 	return false
 }

 // recvRoutine reads msgPackets and reconstructs the message using the channels' "recving" buffer.
 // After a whole message has been assembled, it's pushed to onReceive().
 // Blocks depending on how the connection is throttled.
 func (c *MConnection) recvRoutine() {
 	defer c._recover()

 FOR_LOOP:
 	for {
 		// Block until .recvMonitor says we can read.
 		c.recvMonitor.Limit(maxMsgPacketSize, atomic.LoadInt64(&c.recvRate), true)

 		/*
 			// Peek into bufReader for debugging
 			if numBytes := c.bufReader.Buffered(); numBytes > 0 {
 				log.Info("Peek connection buffer", "numBytes", numBytes, "bytes", log15.Lazy{func() []byte {
 					bytes, err := c.bufReader.Peek(MinInt(numBytes, 100))
 					if err == nil {
 						return bytes
 					} else {
 						log.Warn("Error peeking connection buffer", "error", err)
 						return nil
 					}
 				}})
 			}
 		*/

 		// Read packet type
 		var n int64
 		var err error
 		pktType := wire.ReadByte(c.bufReader, &n, &err)
 		c.recvMonitor.Update(int(n))
 		if err != nil {
 			if c.IsRunning() {
 				log.Warn("Connection failed @ recvRoutine (reading byte)", "conn", c, "error", err)
 				c.stopForError(err)
 			}
 			break FOR_LOOP
 		}

 		// Read more depending on packet type.
 		switch pktType {
 		case packetTypePing:
 			// TODO: prevent abuse, as they cause flush()'s.
 			log.Info("Receive Ping")
 			c.pong <- struct{}{}
 		case packetTypePong:
 			// do nothing
 			log.Info("Receive Pong")
 		case packetTypeMsg:
 			pkt, n, err := msgPacket{}, int64(0), error(nil)
 			wire.ReadBinaryPtr(&pkt, c.bufReader, &n, &err)
 			c.recvMonitor.Update(int(n))
 			if err != nil {
 				if c.IsRunning() {
 					log.Warn("Connection failed @ recvRoutine", "conn", c, "error", err)
 					c.stopForError(err)
 				}
 				break FOR_LOOP
 			}
 			channel, ok := c.channelsIdx[pkt.ChannelID]
 			if !ok || channel == nil {
 				PanicQ(Fmt("Unknown channel %X", pkt.ChannelID))
 			}
 			msgBytes, err := channel.recvMsgPacket(pkt)
 			if err != nil {
 				if c.IsRunning() {
 					log.Warn("Connection failed @ recvRoutine", "conn", c, "error", err)
 					c.stopForError(err)
 				}
 				break FOR_LOOP
 			}
 			if msgBytes != nil {
 				log.Debug("Received bytes", "chID", pkt.ChannelID, "msgBytes", msgBytes)
 				c.onReceive(pkt.ChannelID, msgBytes)
 			}
 		default:
 			PanicSanity(Fmt("Unknown message type %X", pktType))
 		}

 		// TODO: shouldn't this go in the sendRoutine?
 		// Better to send a ping packet when *we* haven't sent anything for a while.
 		c.pingTimer.Reset()
 	}

 	// Cleanup
 	close(c.pong)
 	for _ = range c.pong {
 		// Drain
 	}
 }

 //-----------------------------------------------------------------------------

 type ChannelDescriptor struct {
 	ID                 byte
 	Priority           int
 	SendQueueCapacity  int
 	RecvBufferCapacity int
 }

 func (chDesc *ChannelDescriptor) FillDefaults() {
 	if chDesc.SendQueueCapacity == 0 {
 		chDesc.SendQueueCapacity = defaultSendQueueCapacity
 	}
 	if chDesc.RecvBufferCapacity == 0 {
 		chDesc.RecvBufferCapacity = defaultRecvBufferCapacity
 	}
 }

 // TODO: lowercase.
 // NOTE: not goroutine-safe.
 type Channel struct {
 	conn          *MConnection
 	desc          *ChannelDescriptor
 	id            byte
 	sendQueue     chan []byte
 	sendQueueSize int32 // atomic.
 	recving       []byte
 	sending       []byte
 	priority      int
 	recentlySent  int64 // exponential moving average
 }

 func newChannel(conn *MConnection, desc *ChannelDescriptor) *Channel {
 	desc.FillDefaults()
 	if desc.Priority <= 0 {
 		PanicSanity("Channel default priority must be a postive integer")
 	}
 	return &Channel{
 		conn:      conn,
 		desc:      desc,
 		id:        desc.ID,
 		sendQueue: make(chan []byte, desc.SendQueueCapacity),
 		recving:   make([]byte, 0, desc.RecvBufferCapacity),
 		priority:  desc.Priority,
 	}
 }

 // Queues message to send to this channel.
 // Goroutine-safe
 // Times out (and returns false) after defaultSendTimeoutSeconds
 func (ch *Channel) sendBytes(bytes []byte) bool {
 	timeout := time.NewTimer(defaultSendTimeoutSeconds * time.Second)
 	select {
 	case <-timeout.C:
 		// timeout
 		return false
 	case ch.sendQueue <- bytes:
 		atomic.AddInt32(&ch.sendQueueSize, 1)
 		return true
 	}
 }

 // Queues message to send to this channel.
 // Nonblocking, returns true if successful.
 // Goroutine-safe
 func (ch *Channel) trySendBytes(bytes []byte) bool {
 	select {
 	case ch.sendQueue <- bytes:
 		atomic.AddInt32(&ch.sendQueueSize, 1)
 		return true
 	default:
 		return false
 	}
 }

 // Goroutine-safe
 func (ch *Channel) loadSendQueueSize() (size int) {
 	return int(atomic.LoadInt32(&ch.sendQueueSize))
 }

 // Goroutine-safe
 // Use only as a heuristic.
 func (ch *Channel) canSend() bool {
 	return ch.loadSendQueueSize() < defaultSendQueueCapacity
 }

 // Returns true if any msgPackets are pending to be sent.
 // Call before calling nextMsgPacket()
 // Goroutine-safe
 func (ch *Channel) isSendPending() bool {
 	if len(ch.sending) == 0 {
 		if len(ch.sendQueue) == 0 {
 			return false
 		}
 		ch.sending = <-ch.sendQueue
 	}
 	return true
 }

 // Creates a new msgPacket to send.
 // Not goroutine-safe
 func (ch *Channel) nextMsgPacket() msgPacket {
 	packet := msgPacket{}
 	packet.ChannelID = byte(ch.id)
 	packet.Bytes = ch.sending[:MinInt(maxMsgPacketSize, len(ch.sending))]
 	if len(ch.sending) <= maxMsgPacketSize {
 		packet.EOF = byte(0x01)
 		ch.sending = nil
 		atomic.AddInt32(&ch.sendQueueSize, -1) // decrement sendQueueSize
 	} else {
 		packet.EOF = byte(0x00)
 		ch.sending = ch.sending[MinInt(maxMsgPacketSize, len(ch.sending)):]
 	}
 	return packet
 }

 // Writes next msgPacket to w.
 // Not goroutine-safe
 func (ch *Channel) writeMsgPacketTo(w io.Writer) (n int64, err error) {
 	packet := ch.nextMsgPacket()
 	log.Debug("Write Msg Packet", "conn", ch.conn, "packet", packet)
 	wire.WriteByte(packetTypeMsg, w, &n, &err)
 	wire.WriteBinary(packet, w, &n, &err)
 	if err != nil {
 		ch.recentlySent += n
 	}
 	return
 }

 // Handles incoming msgPackets. Returns a msg bytes if msg is complete.
 // Not goroutine-safe
 func (ch *Channel) recvMsgPacket(packet msgPacket) ([]byte, error) {
 	// log.Debug("Read Msg Packet", "conn", ch.conn, "packet", packet)
 	if wire.MaxBinaryReadSize < len(ch.recving)+len(packet.Bytes) {
 		return nil, wire.ErrBinaryReadSizeOverflow
 	}
 	ch.recving = append(ch.recving, packet.Bytes...)
 	if packet.EOF == byte(0x01) {
 		msgBytes := ch.recving
 		ch.recving = make([]byte, 0, defaultRecvBufferCapacity)
 		return msgBytes, nil
 	}
 	return nil, nil
 }

 // Call this periodically to update stats for throttling purposes.
 // Not goroutine-safe
 func (ch *Channel) updateStats() {
 	// Exponential decay of stats.
 	// TODO: optimize.
 	ch.recentlySent = int64(float64(ch.recentlySent) * 0.5)
 }

 //-----------------------------------------------------------------------------

 const (
 	maxMsgPacketSize = 1024
 	packetTypePing   = byte(0x01)
 	packetTypePong   = byte(0x02)
 	packetTypeMsg    = byte(0x03)
 )

 // Messages in channels are chopped into smaller msgPackets for multiplexing.
 type msgPacket struct {
 	ChannelID byte
 	EOF       byte // 1 means message ends here.
 	Bytes     []byte
 }

 func (p msgPacket) String() string {
 	return fmt.Sprintf("MsgPacket{%X:%X T:%X}", p.ChannelID, p.Bytes, p.EOF)
 }

 //-----------------------------------------------------------------------------

 // Convenience struct for writing typed messages.
 // Reading requires a custom decoder that switches on the first type byte of a byteslice.
 type TypedMessage struct {
 	Type byte
 	Msg  interface{}
 }

 func (tm TypedMessage) String() string {
 	return fmt.Sprintf("TMsg{%X:%v}", tm.Type, tm.Msg)
 }
--- a/listener.go
+++ b/listener.go
@ -0,0 +1,213 @@
 package p2p

 import (
 	"fmt"
 	"net"
 	"strconv"
 	"time"

 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-p2p/upnp"
 )

 type Listener interface {
 	Connections() <-chan net.Conn
 	InternalAddress() *NetAddress
 	ExternalAddress() *NetAddress
 	String() string
 	Stop() bool
 }

 // Implements Listener
 type DefaultListener struct {
 	BaseService

 	listener    net.Listener
 	intAddr     *NetAddress
 	extAddr     *NetAddress
 	connections chan net.Conn
 }

 const (
 	numBufferedConnections = 10
 	defaultExternalPort    = 8770
 	tryListenSeconds       = 5
 )

 func splitHostPort(addr string) (host string, port int) {
 	host, portStr, err := net.SplitHostPort(addr)
 	if err != nil {
 		PanicSanity(err)
 	}
 	port, err = strconv.Atoi(portStr)
 	if err != nil {
 		PanicSanity(err)
 	}
 	return host, port
 }

 // skipUPNP: If true, does not try getUPNPExternalAddress()
 func NewDefaultListener(protocol string, lAddr string, skipUPNP bool) Listener {
 	// Local listen IP & port
 	lAddrIP, lAddrPort := splitHostPort(lAddr)

 	// Create listener
 	var listener net.Listener
 	var err error
 	for i := 0; i < tryListenSeconds; i++ {
 		listener, err = net.Listen(protocol, lAddr)
 		if err == nil {
 			break
 		} else if i < tryListenSeconds-1 {
 			time.Sleep(time.Second * 1)
 		}
 	}
 	if err != nil {
 		PanicCrisis(err)
 	}
 	// Actual listener local IP & port
 	listenerIP, listenerPort := splitHostPort(listener.Addr().String())
 	log.Info("Local listener", "ip", listenerIP, "port", listenerPort)

 	// Determine internal address...
 	var intAddr *NetAddress = NewNetAddressString(lAddr)

 	// Determine external address...
 	var extAddr *NetAddress
 	if !skipUPNP {
 		// If the lAddrIP is INADDR_ANY, try UPnP
 		if lAddrIP == "" || lAddrIP == "0.0.0.0" {
 			extAddr = getUPNPExternalAddress(lAddrPort, listenerPort)
 		}
 	}
 	// Otherwise just use the local address...
 	if extAddr == nil {
 		extAddr = getNaiveExternalAddress(listenerPort)
 	}
 	if extAddr == nil {
 		PanicCrisis("Could not determine external address!")
 	}

 	dl := &DefaultListener{
 		listener:    listener,
 		intAddr:     intAddr,
 		extAddr:     extAddr,
 		connections: make(chan net.Conn, numBufferedConnections),
 	}
 	dl.BaseService = *NewBaseService(log, "DefaultListener", dl)
 	dl.Start() // Started upon construction
 	return dl
 }

 func (l *DefaultListener) OnStart() error {
 	l.BaseService.OnStart()
 	go l.listenRoutine()
 	return nil
 }

 func (l *DefaultListener) OnStop() {
 	l.BaseService.OnStop()
 	l.listener.Close()
 }

 // Accept connections and pass on the channel
 func (l *DefaultListener) listenRoutine() {
 	for {
 		conn, err := l.listener.Accept()

 		if !l.IsRunning() {
 			break // Go to cleanup
 		}

 		// listener wasn't stopped,
 		// yet we encountered an error.
 		if err != nil {
 			PanicCrisis(err)
 		}

 		l.connections <- conn
 	}

 	// Cleanup
 	close(l.connections)
 	for _ = range l.connections {
 		// Drain
 	}
 }

 // A channel of inbound connections.
 // It gets closed when the listener closes.
 func (l *DefaultListener) Connections() <-chan net.Conn {
 	return l.connections
 }

 func (l *DefaultListener) InternalAddress() *NetAddress {
 	return l.intAddr
 }

 func (l *DefaultListener) ExternalAddress() *NetAddress {
 	return l.extAddr
 }

 // NOTE: The returned listener is already Accept()'ing.
 // So it's not suitable to pass into http.Serve().
 func (l *DefaultListener) NetListener() net.Listener {
 	return l.listener
 }

 func (l *DefaultListener) String() string {
 	return fmt.Sprintf("Listener(@%v)", l.extAddr)
 }

 /* external address helpers */

 // UPNP external address discovery & port mapping
 func getUPNPExternalAddress(externalPort, internalPort int) *NetAddress {
 	log.Info("Getting UPNP external address")
 	nat, err := upnp.Discover()
 	if err != nil {
 		log.Info("Could not perform UPNP discover", "error", err)
 		return nil
 	}

 	ext, err := nat.GetExternalAddress()
 	if err != nil {
 		log.Info("Could not get UPNP external address", "error", err)
 		return nil
 	}

 	// UPnP can't seem to get the external port, so let's just be explicit.
 	if externalPort == 0 {
 		externalPort = defaultExternalPort
 	}

 	externalPort, err = nat.AddPortMapping("tcp", externalPort, internalPort, "tendermint", 0)
 	if err != nil {
 		log.Info("Could not add UPNP port mapping", "error", err)
 		return nil
 	}

 	log.Info("Got UPNP external address", "address", ext)
 	return NewNetAddressIPPort(ext, uint16(externalPort))
 }

 // TODO: use syscalls: http://pastebin.com/9exZG4rh
 func getNaiveExternalAddress(port int) *NetAddress {
 	addrs, err := net.InterfaceAddrs()
 	if err != nil {
 		PanicCrisis(Fmt("Could not fetch interface addresses: %v", err))
 	}

 	for _, a := range addrs {
 		ipnet, ok := a.(*net.IPNet)
 		if !ok {
 			continue
 		}
 		v4 := ipnet.IP.To4()
 		if v4 == nil || v4[0] == 127 {
 			continue
 		} // loopback
 		return NewNetAddressIPPort(ipnet.IP, uint16(port))
 	}
 	return nil
 }
--- a/log.go
+++ b/log.go
@ -0,0 +1,7 @@
 package p2p

 import (
 	"github.com/tendermint/go-logger"
 )

 var log = logger.New("module", "p2p")
--- a/netaddress.go
+++ b/netaddress.go
@ -0,0 +1,213 @@
 // Modified for Tendermint
 // Originally Copyright (c) 2013-2014 Conformal Systems LLC.
 // https://github.com/conformal/btcd/blob/master/LICENSE

 package p2p

 import (
 	"fmt"
 	"net"
 	"strconv"
 	"time"

 	. "github.com/tendermint/go-common"
 )

 type NetAddress struct {
 	IP   net.IP
 	Port uint16
 	str  string
 }

 // TODO: socks proxies?
 func NewNetAddress(addr net.Addr) *NetAddress {
 	tcpAddr, ok := addr.(*net.TCPAddr)
 	if !ok {
 		PanicSanity(fmt.Sprintf("Only TCPAddrs are supported. Got: %v", addr))
 	}
 	ip := tcpAddr.IP
 	port := uint16(tcpAddr.Port)
 	return NewNetAddressIPPort(ip, port)
 }

 // Also resolves the host if host is not an IP.
 func NewNetAddressString(addr string) *NetAddress {
 	host, portStr, err := net.SplitHostPort(addr)
 	if err != nil {
 		PanicSanity(err)
 	}
 	ip := net.ParseIP(host)
 	if ip == nil {
 		if len(host) > 0 {
 			ips, err := net.LookupIP(host)
 			if err != nil {
 				PanicSanity(err)
 			}
 			ip = ips[0]
 		}
 	}
 	port, err := strconv.ParseUint(portStr, 10, 16)
 	if err != nil {
 		PanicSanity(err)
 	}
 	na := NewNetAddressIPPort(ip, uint16(port))
 	return na
 }

 func NewNetAddressIPPort(ip net.IP, port uint16) *NetAddress {
 	na := &NetAddress{
 		IP:   ip,
 		Port: port,
 		str: net.JoinHostPort(
 			ip.String(),
 			strconv.FormatUint(uint64(port), 10),
 		),
 	}
 	return na
 }

 func (na *NetAddress) Equals(other interface{}) bool {
 	if o, ok := other.(*NetAddress); ok {
 		return na.String() == o.String()
 	} else {
 		return false
 	}
 }

 func (na *NetAddress) Less(other interface{}) bool {
 	if o, ok := other.(*NetAddress); ok {
 		return na.String() < o.String()
 	} else {
 		PanicSanity("Cannot compare unequal types")
 		return false
 	}
 }

 func (na *NetAddress) String() string {
 	if na.str == "" {
 		na.str = net.JoinHostPort(
 			na.IP.String(),
 			strconv.FormatUint(uint64(na.Port), 10),
 		)
 	}
 	return na.str
 }

 func (na *NetAddress) Dial() (net.Conn, error) {
 	conn, err := net.Dial("tcp", na.String())
 	if err != nil {
 		return nil, err
 	}
 	return conn, nil
 }

 func (na *NetAddress) DialTimeout(timeout time.Duration) (net.Conn, error) {
 	conn, err := net.DialTimeout("tcp", na.String(), timeout)
 	if err != nil {
 		return nil, err
 	}
 	return conn, nil
 }

 func (na *NetAddress) Routable() bool {
 	// TODO(oga) bitcoind doesn't include RFC3849 here, but should we?
 	return na.Valid() && !(na.RFC1918() || na.RFC3927() || na.RFC4862() ||
 		na.RFC4193() || na.RFC4843() || na.Local())
 }

 // For IPv4 these are either a 0 or all bits set address. For IPv6 a zero
 // address or one that matches the RFC3849 documentation address format.
 func (na *NetAddress) Valid() bool {
 	return na.IP != nil && !(na.IP.IsUnspecified() || na.RFC3849() ||
 		na.IP.Equal(net.IPv4bcast))
 }

 func (na *NetAddress) Local() bool {
 	return na.IP.IsLoopback() || zero4.Contains(na.IP)
 }

 func (na *NetAddress) ReachabilityTo(o *NetAddress) int {
 	const (
 		Unreachable = 0
 		Default     = iota
 		Teredo
 		Ipv6_weak
 		Ipv4
 		Ipv6_strong
 		Private
 	)
 	if !na.Routable() {
 		return Unreachable
 	} else if na.RFC4380() {
 		if !o.Routable() {
 			return Default
 		} else if o.RFC4380() {
 			return Teredo
 		} else if o.IP.To4() != nil {
 			return Ipv4
 		} else { // ipv6
 			return Ipv6_weak
 		}
 	} else if na.IP.To4() != nil {
 		if o.Routable() && o.IP.To4() != nil {
 			return Ipv4
 		}
 		return Default
 	} else /* ipv6 */ {
 		var tunnelled bool
 		// Is our v6 is tunnelled?
 		if o.RFC3964() || o.RFC6052() || o.RFC6145() {
 			tunnelled = true
 		}
 		if !o.Routable() {
 			return Default
 		} else if o.RFC4380() {
 			return Teredo
 		} else if o.IP.To4() != nil {
 			return Ipv4
 		} else if tunnelled {
 			// only prioritise ipv6 if we aren't tunnelling it.
 			return Ipv6_weak
 		}
 		return Ipv6_strong
 	}
 }

 // RFC1918: IPv4 Private networks (10.0.0.0/8, 192.168.0.0/16, 172.16.0.0/12)
 // RFC3849: IPv6 Documentation address  (2001:0DB8::/32)
 // RFC3927: IPv4 Autoconfig (169.254.0.0/16)
 // RFC3964: IPv6 6to4 (2002::/16)
 // RFC4193: IPv6 unique local (FC00::/7)
 // RFC4380: IPv6 Teredo tunneling (2001::/32)
 // RFC4843: IPv6 ORCHID: (2001:10::/28)
 // RFC4862: IPv6 Autoconfig (FE80::/64)
 // RFC6052: IPv6 well known prefix (64:FF9B::/96)
 // RFC6145: IPv6 IPv4 translated address ::FFFF:0:0:0/96
 var rfc1918_10 = net.IPNet{IP: net.ParseIP("10.0.0.0"), Mask: net.CIDRMask(8, 32)}
 var rfc1918_192 = net.IPNet{IP: net.ParseIP("192.168.0.0"), Mask: net.CIDRMask(16, 32)}
 var rfc1918_172 = net.IPNet{IP: net.ParseIP("172.16.0.0"), Mask: net.CIDRMask(12, 32)}
 var rfc3849 = net.IPNet{IP: net.ParseIP("2001:0DB8::"), Mask: net.CIDRMask(32, 128)}
 var rfc3927 = net.IPNet{IP: net.ParseIP("169.254.0.0"), Mask: net.CIDRMask(16, 32)}
 var rfc3964 = net.IPNet{IP: net.ParseIP("2002::"), Mask: net.CIDRMask(16, 128)}
 var rfc4193 = net.IPNet{IP: net.ParseIP("FC00::"), Mask: net.CIDRMask(7, 128)}
 var rfc4380 = net.IPNet{IP: net.ParseIP("2001::"), Mask: net.CIDRMask(32, 128)}
 var rfc4843 = net.IPNet{IP: net.ParseIP("2001:10::"), Mask: net.CIDRMask(28, 128)}
 var rfc4862 = net.IPNet{IP: net.ParseIP("FE80::"), Mask: net.CIDRMask(64, 128)}
 var rfc6052 = net.IPNet{IP: net.ParseIP("64:FF9B::"), Mask: net.CIDRMask(96, 128)}
 var rfc6145 = net.IPNet{IP: net.ParseIP("::FFFF:0:0:0"), Mask: net.CIDRMask(96, 128)}
 var zero4 = net.IPNet{IP: net.ParseIP("0.0.0.0"), Mask: net.CIDRMask(8, 32)}

 func (na *NetAddress) RFC1918() bool {
 	return rfc1918_10.Contains(na.IP) ||
 		rfc1918_192.Contains(na.IP) ||
 		rfc1918_172.Contains(na.IP)
 }
 func (na *NetAddress) RFC3849() bool { return rfc3849.Contains(na.IP) }
 func (na *NetAddress) RFC3927() bool { return rfc3927.Contains(na.IP) }
 func (na *NetAddress) RFC3964() bool { return rfc3964.Contains(na.IP) }
 func (na *NetAddress) RFC4193() bool { return rfc4193.Contains(na.IP) }
 func (na *NetAddress) RFC4380() bool { return rfc4380.Contains(na.IP) }
 func (na *NetAddress) RFC4843() bool { return rfc4843.Contains(na.IP) }
 func (na *NetAddress) RFC4862() bool { return rfc4862.Contains(na.IP) }
 func (na *NetAddress) RFC6052() bool { return rfc6052.Contains(na.IP) }
 func (na *NetAddress) RFC6145() bool { return rfc6145.Contains(na.IP) }
--- a/peer.go
+++ b/peer.go
@ -0,0 +1,133 @@
 package p2p

 import (
 	"fmt"
 	"io"
 	"net"

 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-wire"
 )

 type Peer struct {
 	BaseService

 	outbound bool
 	mconn    *MConnection

 	*NodeInfo
 	Key  string
 	Data *CMap // User data.
 }

 // NOTE: blocking
 // Before creating a peer with newPeer(), perform a handshake on connection.
 func peerHandshake(conn net.Conn, ourNodeInfo *NodeInfo) (*NodeInfo, error) {
 	var peerNodeInfo = new(NodeInfo)
 	var err1 error
 	var err2 error
 	Parallel(
 		func() {
 			var n int64
 			wire.WriteBinary(ourNodeInfo, conn, &n, &err1)
 		},
 		func() {
 			var n int64
 			wire.ReadBinary(peerNodeInfo, conn, &n, &err2)
 			log.Notice("Peer handshake", "peerNodeInfo", peerNodeInfo)
 		})
 	if err1 != nil {
 		return nil, err1
 	}
 	if err2 != nil {
 		return nil, err2
 	}
 	return peerNodeInfo, nil
 }

 // NOTE: call peerHandshake on conn before calling newPeer().
 func newPeer(conn net.Conn, peerNodeInfo *NodeInfo, outbound bool, reactorsByCh map[byte]Reactor, chDescs []*ChannelDescriptor, onPeerError func(*Peer, interface{})) *Peer {
 	var p *Peer
 	onReceive := func(chID byte, msgBytes []byte) {
 		reactor := reactorsByCh[chID]
 		if reactor == nil {
 			PanicSanity(Fmt("Unknown channel %X", chID))
 		}
 		reactor.Receive(chID, p, msgBytes)
 	}
 	onError := func(r interface{}) {
 		p.Stop()
 		onPeerError(p, r)
 	}
 	mconn := NewMConnection(conn, chDescs, onReceive, onError)
 	p = &Peer{
 		outbound: outbound,
 		mconn:    mconn,
 		NodeInfo: peerNodeInfo,
 		Key:      peerNodeInfo.PubKey.KeyString(),
 		Data:     NewCMap(),
 	}
 	p.BaseService = *NewBaseService(log, "Peer", p)
 	return p
 }

 func (p *Peer) OnStart() error {
 	p.BaseService.OnStart()
 	_, err := p.mconn.Start()
 	return err
 }

 func (p *Peer) OnStop() {
 	p.BaseService.OnStop()
 	p.mconn.Stop()
 }

 func (p *Peer) Connection() *MConnection {
 	return p.mconn
 }

 func (p *Peer) IsOutbound() bool {
 	return p.outbound
 }

 func (p *Peer) Send(chID byte, msg interface{}) bool {
 	if !p.IsRunning() {
 		return false
 	}
 	return p.mconn.Send(chID, msg)
 }

 func (p *Peer) TrySend(chID byte, msg interface{}) bool {
 	if !p.IsRunning() {
 		return false
 	}
 	return p.mconn.TrySend(chID, msg)
 }

 func (p *Peer) CanSend(chID byte) bool {
 	if !p.IsRunning() {
 		return false
 	}
 	return p.mconn.CanSend(chID)
 }

 func (p *Peer) WriteTo(w io.Writer) (n int64, err error) {
 	wire.WriteString(p.Key, w, &n, &err)
 	return
 }

 func (p *Peer) String() string {
 	if p.outbound {
 		return fmt.Sprintf("Peer{%v %v out}", p.mconn, p.Key[:12])
 	} else {
 		return fmt.Sprintf("Peer{%v %v in}", p.mconn, p.Key[:12])
 	}
 }

 func (p *Peer) Equals(other *Peer) bool {
 	return p.Key == other.Key
 }

 func (p *Peer) Get(key string) interface{} {
 	return p.Data.Get(key)
 }
--- a/peer_set.go
+++ b/peer_set.go
@ -0,0 +1,227 @@
 package p2p

 import (
 	"net"
 	"strings"
 	"sync"
 )

 // IPeerSet has a (immutable) subset of the methods of PeerSet.
 type IPeerSet interface {
 	Has(key string) bool
 	Get(key string) *Peer
 	List() []*Peer
 	Size() int
 }

 //-----------------------------------------------------------------------------

 var (
 	maxPeersPerIPRange = [4]int{11, 7, 5, 3} // ...
 )

 // PeerSet is a special structure for keeping a table of peers.
 // Iteration over the peers is super fast and thread-safe.
 // We also track how many peers per IP range and avoid too many
 type PeerSet struct {
 	mtx          sync.Mutex
 	lookup       map[string]*peerSetItem
 	list         []*Peer
 	connectedIPs *nestedCounter
 }

 type peerSetItem struct {
 	peer  *Peer
 	index int
 }

 func NewPeerSet() *PeerSet {
 	return &PeerSet{
 		lookup:       make(map[string]*peerSetItem),
 		list:         make([]*Peer, 0, 256),
 		connectedIPs: NewNestedCounter(),
 	}
 }

 // Returns false if peer with key (PubKeyEd25519) is already in set
 // or if we have too many peers from the peer's IP range
 func (ps *PeerSet) Add(peer *Peer) error {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 	if ps.lookup[peer.Key] != nil {
 		return ErrSwitchDuplicatePeer
 	}

 	// ensure we havent maxed out connections for the peer's IP range yet
 	// and update the IP range counters
 	if !ps.incrIPRangeCounts(peer.Host()) {
 		return ErrSwitchMaxPeersPerIPRange
 	}

 	index := len(ps.list)
 	// Appending is safe even with other goroutines
 	// iterating over the ps.list slice.
 	ps.list = append(ps.list, peer)
 	ps.lookup[peer.Key] = &peerSetItem{peer, index}
 	return nil
 }

 func (ps *PeerSet) Has(peerKey string) bool {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 	_, ok := ps.lookup[peerKey]
 	return ok
 }

 func (ps *PeerSet) Get(peerKey string) *Peer {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 	item, ok := ps.lookup[peerKey]
 	if ok {
 		return item.peer
 	} else {
 		return nil
 	}
 }

 func (ps *PeerSet) Remove(peer *Peer) {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 	item := ps.lookup[peer.Key]
 	if item == nil {
 		return
 	}

 	// update the IP range counters
 	ps.decrIPRangeCounts(peer.Host())

 	index := item.index
 	// Copy the list but without the last element.
 	// (we must copy because we're mutating the list)
 	newList := make([]*Peer, len(ps.list)-1)
 	copy(newList, ps.list)
 	// If it's the last peer, that's an easy special case.
 	if index == len(ps.list)-1 {
 		ps.list = newList
 		delete(ps.lookup, peer.Key)
 		return
 	}

 	// Move the last item from ps.list to "index" in list.
 	lastPeer := ps.list[len(ps.list)-1]
 	lastPeerKey := lastPeer.Key
 	lastPeerItem := ps.lookup[lastPeerKey]
 	newList[index] = lastPeer
 	lastPeerItem.index = index
 	ps.list = newList
 	delete(ps.lookup, peer.Key)

 }

 func (ps *PeerSet) Size() int {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 	return len(ps.list)
 }

 // threadsafe list of peers.
 func (ps *PeerSet) List() []*Peer {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 	return ps.list
 }

 //-----------------------------------------------------------------------------
 // track the number of IPs we're connected to for each IP address range

 // forms an IP address hierarchy tree with counts
 // the struct itself is not thread safe and should always only be accessed with the ps.mtx locked
 type nestedCounter struct {
 	count    int
 	children map[string]*nestedCounter
 }

 func NewNestedCounter() *nestedCounter {
 	nc := new(nestedCounter)
 	nc.children = make(map[string]*nestedCounter)
 	return nc
 }

 // Check if we have too many IPs in the IP range of the incoming connection
 // Thread safe
 func (ps *PeerSet) HasMaxForIPRange(conn net.Conn) (ok bool) {
 	ps.mtx.Lock()
 	defer ps.mtx.Unlock()
 	ip, _, _ := net.SplitHostPort(conn.RemoteAddr().String())
 	ipBytes := strings.Split(ip, ".")

 	c := ps.connectedIPs
 	for i, ipByte := range ipBytes {
 		if c, ok = c.children[ipByte]; !ok {
 			return false
 		}
 		if maxPeersPerIPRange[i] <= c.count {
 			return true
 		}
 	}
 	return false
 }

 // Increments counts for this address' IP range
 // Returns false if we already have enough connections
 // Not thread safe (only called by ps.Add())
 func (ps *PeerSet) incrIPRangeCounts(address string) bool {
 	addrParts := strings.Split(address, ".")

 	c := ps.connectedIPs
 	return incrNestedCounters(c, addrParts, 0)
 }

 // Recursively descend the IP hierarchy, checking if we have
 // max peers for each range and incrementing if not.
 // Returns false if incr failed because max peers reached for some range counter.
 func incrNestedCounters(c *nestedCounter, ipBytes []string, index int) bool {
 	ipByte := ipBytes[index]
 	child := c.children[ipByte]
 	if child == nil {
 		child = NewNestedCounter()
 		c.children[ipByte] = child
 	}
 	if index+1 < len(ipBytes) {
 		if !incrNestedCounters(child, ipBytes, index+1) {
 			return false
 		}
 	}
 	if maxPeersPerIPRange[index] <= child.count {
 		return false
 	} else {
 		child.count += 1
 		return true
 	}
 }

 // Decrement counts for this address' IP range
 func (ps *PeerSet) decrIPRangeCounts(address string) {
 	addrParts := strings.Split(address, ".")

 	c := ps.connectedIPs
 	decrNestedCounters(c, addrParts, 0)
 }

 // Recursively descend the IP hierarchy, decrementing by one.
 // If the counter is zero, deletes the child.
 func decrNestedCounters(c *nestedCounter, ipBytes []string, index int) {
 	ipByte := ipBytes[index]
 	child := c.children[ipByte]
 	if child == nil {
 		log.Error("p2p/peer_set decrNestedCounters encountered a missing child counter")
 		return
 	}
 	if index+1 < len(ipBytes) {
 		decrNestedCounters(child, ipBytes, index+1)
 	}
 	child.count -= 1
 	if child.count <= 0 {
 		delete(c.children, ipByte)
 	}
 }
--- a/peer_set_test.go
+++ b/peer_set_test.go
@ -0,0 +1,168 @@
 package p2p

 import (
 	"math/rand"
 	"strings"
 	"testing"

 	. "github.com/tendermint/go-common"
 )

 // Returns an empty dummy peer
 func randPeer() *Peer {
 	return &Peer{
 		Key: RandStr(12),
 		NodeInfo: &NodeInfo{
 			Address: Fmt("%v.%v.%v.%v:46656", rand.Int()%256, rand.Int()%256, rand.Int()%256, rand.Int()%256),
 		},
 	}
 }

 func TestAddRemoveOne(t *testing.T) {
 	peerSet := NewPeerSet()

 	peer := randPeer()
 	err := peerSet.Add(peer)
 	if err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	if peerSet.Size() != 1 {
 		t.Errorf("Failed to add new peer and increment size")
 	}

 	peerSet.Remove(peer)
 	if peerSet.Has(peer.Key) {
 		t.Errorf("Failed to remove peer")
 	}
 	if peerSet.Size() != 0 {
 		t.Errorf("Failed to remove peer and decrement size")
 	}
 }

 func TestAddRemoveMany(t *testing.T) {
 	peerSet := NewPeerSet()

 	peers := []*Peer{}
 	N := 100
 	maxPeersPerIPRange = [4]int{N, N, N, N}
 	for i := 0; i < N; i++ {
 		peer := randPeer()
 		if err := peerSet.Add(peer); err != nil {
 			t.Errorf("Failed to add new peer")
 		}
 		if peerSet.Size() != i+1 {
 			t.Errorf("Failed to add new peer and increment size")
 		}
 		peers = append(peers, peer)
 	}

 	for i, peer := range peers {
 		peerSet.Remove(peer)
 		if peerSet.Has(peer.Key) {
 			t.Errorf("Failed to remove peer")
 		}
 		if peerSet.Size() != len(peers)-i-1 {
 			t.Errorf("Failed to remove peer and decrement size")
 		}
 	}
 }

 func newPeerInIPRange(ipBytes ...string) *Peer {
 	ips := make([]string, 4)
 	for i, ipByte := range ipBytes {
 		ips[i] = ipByte
 	}
 	for i := len(ipBytes); i < 4; i++ {
 		ips[i] = Fmt("%v", rand.Int()%256)
 	}
 	ipS := strings.Join(ips, ".")
 	return &Peer{
 		Key: RandStr(12),
 		NodeInfo: &NodeInfo{
 			Address: ipS + ":46656",
 		},
 	}
 }

 func TestIPRanges(t *testing.T) {
 	peerSet := NewPeerSet()

 	// test  /8
 	maxPeersPerIPRange = [4]int{2, 2, 2, 2}
 	peer := newPeerInIPRange("54", "1")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	peer = newPeerInIPRange("54", "2")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	peer = newPeerInIPRange("54", "3")
 	if err := peerSet.Add(peer); err == nil {
 		t.Errorf("Added peer when we shouldn't have")
 	}
 	peer = newPeerInIPRange("55", "1")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}

 	// test  /16
 	peerSet = NewPeerSet()
 	maxPeersPerIPRange = [4]int{3, 2, 1, 1}
 	peer = newPeerInIPRange("54", "112", "1")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	peer = newPeerInIPRange("54", "112", "2")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	peer = newPeerInIPRange("54", "112", "3")
 	if err := peerSet.Add(peer); err == nil {
 		t.Errorf("Added peer when we shouldn't have")
 	}
 	peer = newPeerInIPRange("54", "113", "1")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}

 	// test  /24
 	peerSet = NewPeerSet()
 	maxPeersPerIPRange = [4]int{5, 3, 2, 1}
 	peer = newPeerInIPRange("54", "112", "11", "1")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	peer = newPeerInIPRange("54", "112", "11", "2")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	peer = newPeerInIPRange("54", "112", "11", "3")
 	if err := peerSet.Add(peer); err == nil {
 		t.Errorf("Added peer when we shouldn't have")
 	}
 	peer = newPeerInIPRange("54", "112", "12", "1")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}

 	// test  /32
 	peerSet = NewPeerSet()
 	maxPeersPerIPRange = [4]int{11, 7, 5, 2}
 	peer = newPeerInIPRange("54", "112", "11", "10")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	peer = newPeerInIPRange("54", "112", "11", "10")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 	peer = newPeerInIPRange("54", "112", "11", "10")
 	if err := peerSet.Add(peer); err == nil {
 		t.Errorf("Added peer when we shouldn't have")
 	}
 	peer = newPeerInIPRange("54", "112", "11", "11")
 	if err := peerSet.Add(peer); err != nil {
 		t.Errorf("Failed to add new peer")
 	}
 }
--- a/pex_reactor.go
+++ b/pex_reactor.go
@ -0,0 +1,255 @@
 package p2p

 import (
 	"bytes"
 	"errors"
 	"fmt"
 	"math/rand"
 	"reflect"
 	"time"

 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-wire"
 )

 var pexErrInvalidMessage = errors.New("Invalid PEX message")

 const (
 	PexChannel               = byte(0x00)
 	ensurePeersPeriodSeconds = 30
 	minNumOutboundPeers      = 10
 )

 /*
 PEXReactor handles PEX (peer exchange) and ensures that an
 adequate number of peers are connected to the switch.
 */
 type PEXReactor struct {
 	BaseReactor

 	sw   *Switch
 	book *AddrBook
 }

 func NewPEXReactor(book *AddrBook) *PEXReactor {
 	pexR := &PEXReactor{
 		book: book,
 	}
 	pexR.BaseReactor = *NewBaseReactor(log, "PEXReactor", pexR)
 	return pexR
 }

 func (pexR *PEXReactor) OnStart() error {
 	pexR.BaseReactor.OnStart()
 	go pexR.ensurePeersRoutine()
 	return nil
 }

 func (pexR *PEXReactor) OnStop() {
 	pexR.BaseReactor.OnStop()
 }

 // Implements Reactor
 func (pexR *PEXReactor) GetChannels() []*ChannelDescriptor {
 	return []*ChannelDescriptor{
 		&ChannelDescriptor{
 			ID:                PexChannel,
 			Priority:          1,
 			SendQueueCapacity: 10,
 		},
 	}
 }

 // Implements Reactor
 func (pexR *PEXReactor) AddPeer(peer *Peer) {
 	// Add the peer to the address book
 	netAddr := NewNetAddressString(peer.Address)
 	if peer.IsOutbound() {
 		if pexR.book.NeedMoreAddrs() {
 			pexR.RequestPEX(peer)
 		}
 	} else {
 		// For inbound connections, the peer is its own source
 		// (For outbound peers, the address is already in the books)
 		pexR.book.AddAddress(netAddr, netAddr)
 	}
 }

 // Implements Reactor
 func (pexR *PEXReactor) RemovePeer(peer *Peer, reason interface{}) {
 	// TODO
 }

 // Implements Reactor
 // Handles incoming PEX messages.
 func (pexR *PEXReactor) Receive(chID byte, src *Peer, msgBytes []byte) {

 	// decode message
 	_, msg, err := DecodeMessage(msgBytes)
 	if err != nil {
 		log.Warn("Error decoding message", "error", err)
 		return
 	}
 	log.Notice("Received message", "msg", msg)

 	switch msg := msg.(type) {
 	case *pexRequestMessage:
 		// src requested some peers.
 		// TODO: prevent abuse.
 		pexR.SendAddrs(src, pexR.book.GetSelection())
 	case *pexAddrsMessage:
 		// We received some peer addresses from src.
 		// TODO: prevent abuse.
 		// (We don't want to get spammed with bad peers)
 		srcAddr := src.Connection().RemoteAddress
 		for _, addr := range msg.Addrs {
 			pexR.book.AddAddress(addr, srcAddr)
 		}
 	default:
 		log.Warn(Fmt("Unknown message type %v", reflect.TypeOf(msg)))
 	}

 }

 // Asks peer for more addresses.
 func (pexR *PEXReactor) RequestPEX(peer *Peer) {
 	peer.Send(PexChannel, &pexRequestMessage{})
 }

 func (pexR *PEXReactor) SendAddrs(peer *Peer, addrs []*NetAddress) {
 	peer.Send(PexChannel, &pexAddrsMessage{Addrs: addrs})
 }

 // Ensures that sufficient peers are connected. (continuous)
 func (pexR *PEXReactor) ensurePeersRoutine() {
 	// Randomize when routine starts
 	time.Sleep(time.Duration(rand.Int63n(500*ensurePeersPeriodSeconds)) * time.Millisecond)

 	// fire once immediately.
 	pexR.ensurePeers()
 	// fire periodically
 	timer := NewRepeatTimer("pex", ensurePeersPeriodSeconds*time.Second)
 FOR_LOOP:
 	for {
 		select {
 		case <-timer.Ch:
 			pexR.ensurePeers()
 		case <-pexR.Quit:
 			break FOR_LOOP
 		}
 	}

 	// Cleanup
 	timer.Stop()
 }

 // Ensures that sufficient peers are connected. (once)
 func (pexR *PEXReactor) ensurePeers() {
 	numOutPeers, _, numDialing := pexR.Switch.NumPeers()
 	numToDial := minNumOutboundPeers - (numOutPeers + numDialing)
 	log.Info("Ensure peers", "numOutPeers", numOutPeers, "numDialing", numDialing, "numToDial", numToDial)
 	if numToDial <= 0 {
 		return
 	}
 	toDial := NewCMap()

 	// Try to pick numToDial addresses to dial.
 	// TODO: improve logic.
 	for i := 0; i < numToDial; i++ {
 		newBias := MinInt(numOutPeers, 8)*10 + 10
 		var picked *NetAddress
 		// Try to fetch a new peer 3 times.
 		// This caps the maximum number of tries to 3 * numToDial.
 		for j := 0; j < 3; j++ {
 			try := pexR.book.PickAddress(newBias)
 			if try == nil {
 				break
 			}
 			alreadySelected := toDial.Has(try.IP.String())
 			alreadyDialing := pexR.Switch.IsDialing(try)
 			alreadyConnected := pexR.Switch.Peers().Has(try.IP.String())
 			if alreadySelected || alreadyDialing || alreadyConnected {
 				/*
 					log.Info("Cannot dial address", "addr", try,
 						"alreadySelected", alreadySelected,
 						"alreadyDialing", alreadyDialing,
 						"alreadyConnected", alreadyConnected)
 				*/
 				continue
 			} else {
 				log.Info("Will dial address", "addr", try)
 				picked = try
 				break
 			}
 		}
 		if picked == nil {
 			continue
 		}
 		toDial.Set(picked.IP.String(), picked)
 	}

 	// Dial picked addresses
 	for _, item := range toDial.Values() {
 		go func(picked *NetAddress) {
 			_, err := pexR.Switch.DialPeerWithAddress(picked)
 			if err != nil {
 				pexR.book.MarkAttempt(picked)
 			}
 		}(item.(*NetAddress))
 	}

 	// If we need more addresses, pick a random peer and ask for more.
 	if pexR.book.NeedMoreAddrs() {
 		if peers := pexR.Switch.Peers().List(); len(peers) > 0 {
 			i := rand.Int() % len(peers)
 			peer := peers[i]
 			log.Info("No addresses to dial. Sending pexRequest to random peer", "peer", peer)
 			pexR.RequestPEX(peer)
 		}
 	}
 }

 //-----------------------------------------------------------------------------
 // Messages

 const (
 	msgTypeRequest = byte(0x01)
 	msgTypeAddrs   = byte(0x02)
 )

 type PexMessage interface{}

 var _ = wire.RegisterInterface(
 	struct{ PexMessage }{},
 	wire.ConcreteType{&pexRequestMessage{}, msgTypeRequest},
 	wire.ConcreteType{&pexAddrsMessage{}, msgTypeAddrs},
 )

 func DecodeMessage(bz []byte) (msgType byte, msg PexMessage, err error) {
 	msgType = bz[0]
 	n := new(int64)
 	r := bytes.NewReader(bz)
 	msg = wire.ReadBinary(struct{ PexMessage }{}, r, n, &err).(struct{ PexMessage }).PexMessage
 	return
 }

 /*
 A pexRequestMessage requests additional peer addresses.
 */
 type pexRequestMessage struct {
 }

 func (m *pexRequestMessage) String() string {
 	return "[pexRequest]"
 }

 /*
 A message with announced peer addresses.
 */
 type pexAddrsMessage struct {
 	Addrs []*NetAddress
 }

 func (m *pexAddrsMessage) String() string {
 	return fmt.Sprintf("[pexAddrs %v]", m.Addrs)
 }
--- a/secret_connection.go
+++ b/secret_connection.go
@ -0,0 +1,346 @@
 // Uses nacl's secret_box to encrypt a net.Conn.
 // It is (meant to be) an implementation of the STS protocol.
 // Note we do not (yet) assume that a remote peer's pubkey
 // is known ahead of time, and thus we are technically
 // still vulnerable to MITM. (TODO!)
 // See docs/sts-final.pdf for more info
 package p2p

 import (
 	"bytes"
 	crand "crypto/rand"
 	"crypto/sha256"
 	"encoding/binary"
 	"errors"
 	"io"
 	"net"
 	"time"

 	"golang.org/x/crypto/nacl/box"
 	"golang.org/x/crypto/nacl/secretbox"
 	"golang.org/x/crypto/ripemd160"

 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-crypto"
 	"github.com/tendermint/go-wire"
 )

 // 2 + 1024 == 1026 total frame size
 const dataLenSize = 2 // uint16 to describe the length, is <= dataMaxSize
 const dataMaxSize = 1024
 const totalFrameSize = dataMaxSize + dataLenSize
 const sealedFrameSize = totalFrameSize + secretbox.Overhead
 const authSigMsgSize = (32 + 1) + (64 + 1) // fixed size (length prefixed) byte arrays

 // Implements net.Conn
 type SecretConnection struct {
 	conn       io.ReadWriteCloser
 	recvBuffer []byte
 	recvNonce  *[24]byte
 	sendNonce  *[24]byte
 	remPubKey  crypto.PubKeyEd25519
 	shrSecret  *[32]byte // shared secret
 }

 // Performs handshake and returns a new authenticated SecretConnection.
 // Returns nil if error in handshake.
 // Caller should call conn.Close()
 // See docs/sts-final.pdf for more information.
 func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKeyEd25519) (*SecretConnection, error) {

 	locPubKey := locPrivKey.PubKey().(crypto.PubKeyEd25519)

 	// Generate ephemeral keys for perfect forward secrecy.
 	locEphPub, locEphPriv := genEphKeys()

 	// Write local ephemeral pubkey and receive one too.
 	// NOTE: every 32-byte string is accepted as a Curve25519 public key
 	// (see DJB's Curve25519 paper: http://cr.yp.to/ecdh/curve25519-20060209.pdf)
 	remEphPub, err := shareEphPubKey(conn, locEphPub)
 	if err != nil {
 		return nil, err
 	}

 	// Compute common shared secret.
 	shrSecret := computeSharedSecret(remEphPub, locEphPriv)

 	// Sort by lexical order.
 	loEphPub, hiEphPub := sort32(locEphPub, remEphPub)

 	// Generate nonces to use for secretbox.
 	recvNonce, sendNonce := genNonces(loEphPub, hiEphPub, locEphPub == loEphPub)

 	// Generate common challenge to sign.
 	challenge := genChallenge(loEphPub, hiEphPub)

 	// Construct SecretConnection.
 	sc := &SecretConnection{
 		conn:       conn,
 		recvBuffer: nil,
 		recvNonce:  recvNonce,
 		sendNonce:  sendNonce,
 		shrSecret:  shrSecret,
 	}

 	// Sign the challenge bytes for authentication.
 	locSignature := signChallenge(challenge, locPrivKey)

 	// Share (in secret) each other's pubkey & challenge signature
 	authSigMsg, err := shareAuthSignature(sc, locPubKey, locSignature)
 	if err != nil {
 		return nil, err
 	}
 	remPubKey, remSignature := authSigMsg.Key, authSigMsg.Sig
 	if !remPubKey.VerifyBytes(challenge[:], remSignature) {
 		return nil, errors.New("Challenge verification failed")
 	}

 	// We've authorized.
 	sc.remPubKey = remPubKey
 	return sc, nil
 }

 // Returns authenticated remote pubkey
 func (sc *SecretConnection) RemotePubKey() crypto.PubKeyEd25519 {
 	return sc.remPubKey
 }

 // Writes encrypted frames of `sealedFrameSize`
 // CONTRACT: data smaller than dataMaxSize is read atomically.
 func (sc *SecretConnection) Write(data []byte) (n int, err error) {
 	for 0 < len(data) {
 		var frame []byte = make([]byte, totalFrameSize)
 		var chunk []byte
 		if dataMaxSize < len(data) {
 			chunk = data[:dataMaxSize]
 			data = data[dataMaxSize:]
 		} else {
 			chunk = data
 			data = nil
 		}
 		chunkLength := len(chunk)
 		binary.BigEndian.PutUint16(frame, uint16(chunkLength))
 		copy(frame[dataLenSize:], chunk)

 		// encrypt the frame
 		var sealedFrame = make([]byte, sealedFrameSize)
 		secretbox.Seal(sealedFrame[:0], frame, sc.sendNonce, sc.shrSecret)
 		// fmt.Printf("secretbox.Seal(sealed:%X,sendNonce:%X,shrSecret:%X\n", sealedFrame, sc.sendNonce, sc.shrSecret)
 		incr2Nonce(sc.sendNonce)
 		// end encryption

 		_, err := sc.conn.Write(sealedFrame)
 		if err != nil {
 			return n, err
 		} else {
 			n += len(chunk)
 		}
 	}
 	return
 }

 // CONTRACT: data smaller than dataMaxSize is read atomically.
 func (sc *SecretConnection) Read(data []byte) (n int, err error) {
 	if 0 < len(sc.recvBuffer) {
 		n_ := copy(data, sc.recvBuffer)
 		sc.recvBuffer = sc.recvBuffer[n_:]
 		return
 	}

 	sealedFrame := make([]byte, sealedFrameSize)
 	_, err = io.ReadFull(sc.conn, sealedFrame)
 	if err != nil {
 		return
 	}

 	// decrypt the frame
 	var frame = make([]byte, totalFrameSize)
 	// fmt.Printf("secretbox.Open(sealed:%X,recvNonce:%X,shrSecret:%X\n", sealedFrame, sc.recvNonce, sc.shrSecret)
 	_, ok := secretbox.Open(frame[:0], sealedFrame, sc.recvNonce, sc.shrSecret)
 	if !ok {
 		return n, errors.New("Failed to decrypt SecretConnection")
 	}
 	incr2Nonce(sc.recvNonce)
 	// end decryption

 	var chunkLength = binary.BigEndian.Uint16(frame) // read the first two bytes
 	if chunkLength > dataMaxSize {
 		return 0, errors.New("chunkLength is greater than dataMaxSize")
 	}
 	var chunk = frame[dataLenSize : dataLenSize+chunkLength]

 	n = copy(data, chunk)
 	sc.recvBuffer = chunk[n:]
 	return
 }

 // Implements net.Conn
 func (sc *SecretConnection) Close() error                  { return sc.conn.Close() }
 func (sc *SecretConnection) LocalAddr() net.Addr           { return sc.conn.(net.Conn).LocalAddr() }
 func (sc *SecretConnection) RemoteAddr() net.Addr          { return sc.conn.(net.Conn).RemoteAddr() }
 func (sc *SecretConnection) SetDeadline(t time.Time) error { return sc.conn.(net.Conn).SetDeadline(t) }
 func (sc *SecretConnection) SetReadDeadline(t time.Time) error {
 	return sc.conn.(net.Conn).SetReadDeadline(t)
 }
 func (sc *SecretConnection) SetWriteDeadline(t time.Time) error {
 	return sc.conn.(net.Conn).SetWriteDeadline(t)
 }

 func genEphKeys() (ephPub, ephPriv *[32]byte) {
 	var err error
 	ephPub, ephPriv, err = box.GenerateKey(crand.Reader)
 	if err != nil {
 		PanicCrisis("Could not generate ephemeral keypairs")
 	}
 	return
 }

 func shareEphPubKey(conn io.ReadWriteCloser, locEphPub *[32]byte) (remEphPub *[32]byte, err error) {
 	var err1, err2 error

 	Parallel(
 		func() {
 			_, err1 = conn.Write(locEphPub[:])
 		},
 		func() {
 			remEphPub = new([32]byte)
 			_, err2 = io.ReadFull(conn, remEphPub[:])
 		},
 	)

 	if err1 != nil {
 		return nil, err1
 	}
 	if err2 != nil {
 		return nil, err2
 	}

 	return remEphPub, nil
 }

 func computeSharedSecret(remPubKey, locPrivKey *[32]byte) (shrSecret *[32]byte) {
 	shrSecret = new([32]byte)
 	box.Precompute(shrSecret, remPubKey, locPrivKey)
 	return
 }

 func sort32(foo, bar *[32]byte) (lo, hi *[32]byte) {
 	if bytes.Compare(foo[:], bar[:]) < 0 {
 		lo = foo
 		hi = bar
 	} else {
 		lo = bar
 		hi = foo
 	}
 	return
 }

 func genNonces(loPubKey, hiPubKey *[32]byte, locIsLo bool) (recvNonce, sendNonce *[24]byte) {
 	nonce1 := hash24(append(loPubKey[:], hiPubKey[:]...))
 	nonce2 := new([24]byte)
 	copy(nonce2[:], nonce1[:])
 	nonce2[len(nonce2)-1] ^= 0x01
 	if locIsLo {
 		recvNonce = nonce1
 		sendNonce = nonce2
 	} else {
 		recvNonce = nonce2
 		sendNonce = nonce1
 	}
 	return
 }

 func genChallenge(loPubKey, hiPubKey *[32]byte) (challenge *[32]byte) {
 	return hash32(append(loPubKey[:], hiPubKey[:]...))
 }

 func signChallenge(challenge *[32]byte, locPrivKey crypto.PrivKeyEd25519) (signature crypto.SignatureEd25519) {
 	signature = locPrivKey.Sign(challenge[:]).(crypto.SignatureEd25519)
 	return
 }

 type authSigMessage struct {
 	Key crypto.PubKeyEd25519
 	Sig crypto.SignatureEd25519
 }

 func shareAuthSignature(sc *SecretConnection, pubKey crypto.PubKeyEd25519, signature crypto.SignatureEd25519) (*authSigMessage, error) {
 	var recvMsg authSigMessage
 	var err1, err2 error

 	Parallel(
 		func() {
 			msgBytes := wire.BinaryBytes(authSigMessage{pubKey, signature})
 			_, err1 = sc.Write(msgBytes)
 		},
 		func() {
 			readBuffer := make([]byte, authSigMsgSize)
 			_, err2 = io.ReadFull(sc, readBuffer)
 			if err2 != nil {
 				return
 			}
 			n := int64(0) // not used.
 			recvMsg = wire.ReadBinary(authSigMessage{}, bytes.NewBuffer(readBuffer), &n, &err2).(authSigMessage)
 		})

 	if err1 != nil {
 		return nil, err1
 	}
 	if err2 != nil {
 		return nil, err2
 	}

 	return &recvMsg, nil
 }

 func verifyChallengeSignature(challenge *[32]byte, remPubKey crypto.PubKeyEd25519, remSignature crypto.SignatureEd25519) bool {
 	return remPubKey.VerifyBytes(challenge[:], remSignature)
 }

 //--------------------------------------------------------------------------------

 // sha256
 func hash32(input []byte) (res *[32]byte) {
 	hasher := sha256.New()
 	hasher.Write(input) // does not error
 	resSlice := hasher.Sum(nil)
 	res = new([32]byte)
 	copy(res[:], resSlice)
 	return
 }

 // We only fill in the first 20 bytes with ripemd160
 func hash24(input []byte) (res *[24]byte) {
 	hasher := ripemd160.New()
 	hasher.Write(input) // does not error
 	resSlice := hasher.Sum(nil)
 	res = new([24]byte)
 	copy(res[:], resSlice)
 	return
 }

 // ripemd160
 func hash20(input []byte) (res *[20]byte) {
 	hasher := ripemd160.New()
 	hasher.Write(input) // does not error
 	resSlice := hasher.Sum(nil)
 	res = new([20]byte)
 	copy(res[:], resSlice)
 	return
 }

 // increment nonce big-endian by 2 with wraparound.
 func incr2Nonce(nonce *[24]byte) {
 	incrNonce(nonce)
 	incrNonce(nonce)
 }

 // increment nonce big-endian by 1 with wraparound.
 func incrNonce(nonce *[24]byte) {
 	for i := 23; 0 <= i; i-- {
 		nonce[i] += 1
 		if nonce[i] != 0 {
 			return
 		}
 	}
 }
--- a/secret_connection_test.go
+++ b/secret_connection_test.go
@ -0,0 +1,202 @@
 package p2p

 import (
 	"bytes"
 	"io"
 	"testing"

 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-crypto"
 )

 type dummyConn struct {
 	*io.PipeReader
 	*io.PipeWriter
 }

 func (drw dummyConn) Close() (err error) {
 	err2 := drw.PipeWriter.CloseWithError(io.EOF)
 	err1 := drw.PipeReader.Close()
 	if err2 != nil {
 		return err
 	}
 	return err1
 }

 // Each returned ReadWriteCloser is akin to a net.Connection
 func makeDummyConnPair() (fooConn, barConn dummyConn) {
 	barReader, fooWriter := io.Pipe()
 	fooReader, barWriter := io.Pipe()
 	return dummyConn{fooReader, fooWriter}, dummyConn{barReader, barWriter}
 }

 func makeSecretConnPair(tb testing.TB) (fooSecConn, barSecConn *SecretConnection) {
 	fooConn, barConn := makeDummyConnPair()
 	fooPrvKey := crypto.GenPrivKeyEd25519()
 	fooPubKey := fooPrvKey.PubKey().(crypto.PubKeyEd25519)
 	barPrvKey := crypto.GenPrivKeyEd25519()
 	barPubKey := barPrvKey.PubKey().(crypto.PubKeyEd25519)

 	Parallel(
 		func() {
 			var err error
 			fooSecConn, err = MakeSecretConnection(fooConn, fooPrvKey)
 			if err != nil {
 				tb.Errorf("Failed to establish SecretConnection for foo: %v", err)
 				return
 			}
 			remotePubBytes := fooSecConn.RemotePubKey()
 			if !bytes.Equal(remotePubBytes[:], barPubKey[:]) {
 				tb.Errorf("Unexpected fooSecConn.RemotePubKey.  Expected %v, got %v",
 					barPubKey, fooSecConn.RemotePubKey())
 			}
 		},
 		func() {
 			var err error
 			barSecConn, err = MakeSecretConnection(barConn, barPrvKey)
 			if barSecConn == nil {
 				tb.Errorf("Failed to establish SecretConnection for bar: %v", err)
 				return
 			}
 			remotePubBytes := barSecConn.RemotePubKey()
 			if !bytes.Equal(remotePubBytes[:], fooPubKey[:]) {
 				tb.Errorf("Unexpected barSecConn.RemotePubKey.  Expected %v, got %v",
 					fooPubKey, barSecConn.RemotePubKey())
 			}
 		})

 	return
 }

 func TestSecretConnectionHandshake(t *testing.T) {
 	fooSecConn, barSecConn := makeSecretConnPair(t)
 	fooSecConn.Close()
 	barSecConn.Close()
 }

 func TestSecretConnectionReadWrite(t *testing.T) {
 	fooConn, barConn := makeDummyConnPair()
 	fooWrites, barWrites := []string{}, []string{}
 	fooReads, barReads := []string{}, []string{}

 	// Pre-generate the things to write (for foo & bar)
 	for i := 0; i < 100; i++ {
 		fooWrites = append(fooWrites, RandStr((RandInt()%(dataMaxSize*5))+1))
 		barWrites = append(barWrites, RandStr((RandInt()%(dataMaxSize*5))+1))
 	}

 	// A helper that will run with (fooConn, fooWrites, fooReads) and vice versa
 	genNodeRunner := func(nodeConn dummyConn, nodeWrites []string, nodeReads *[]string) func() {
 		return func() {
 			// Node handskae
 			nodePrvKey := crypto.GenPrivKeyEd25519()
 			nodeSecretConn, err := MakeSecretConnection(nodeConn, nodePrvKey)
 			if err != nil {
 				t.Errorf("Failed to establish SecretConnection for node: %v", err)
 				return
 			}
 			// In parallel, handle reads and writes
 			Parallel(
 				func() {
 					// Node writes
 					for _, nodeWrite := range nodeWrites {
 						n, err := nodeSecretConn.Write([]byte(nodeWrite))
 						if err != nil {
 							t.Errorf("Failed to write to nodeSecretConn: %v", err)
 							return
 						}
 						if n != len(nodeWrite) {
 							t.Errorf("Failed to write all bytes. Expected %v, wrote %v", len(nodeWrite), n)
 							return
 						}
 					}
 					nodeConn.PipeWriter.Close()
 				},
 				func() {
 					// Node reads
 					readBuffer := make([]byte, dataMaxSize)
 					for {
 						n, err := nodeSecretConn.Read(readBuffer)
 						if err == io.EOF {
 							return
 						} else if err != nil {
 							t.Errorf("Failed to read from nodeSecretConn: %v", err)
 							return
 						}
 						*nodeReads = append(*nodeReads, string(readBuffer[:n]))
 					}
 					nodeConn.PipeReader.Close()
 				})
 		}
 	}

 	// Run foo & bar in parallel
 	Parallel(
 		genNodeRunner(fooConn, fooWrites, &fooReads),
 		genNodeRunner(barConn, barWrites, &barReads),
 	)

 	// A helper to ensure that the writes and reads match.
 	// Additionally, small writes (<= dataMaxSize) must be atomically read.
 	compareWritesReads := func(writes []string, reads []string) {
 		for {
 			// Pop next write & corresponding reads
 			var read, write string = "", writes[0]
 			var readCount = 0
 			for _, readChunk := range reads {
 				read += readChunk
 				readCount += 1
 				if len(write) <= len(read) {
 					break
 				}
 				if len(write) <= dataMaxSize {
 					break // atomicity of small writes
 				}
 			}
 			// Compare
 			if write != read {
 				t.Errorf("Expected to read %X, got %X", write, read)
 			}
 			// Iterate
 			writes = writes[1:]
 			reads = reads[readCount:]
 			if len(writes) == 0 {
 				break
 			}
 		}
 	}

 	compareWritesReads(fooWrites, barReads)
 	compareWritesReads(barWrites, fooReads)

 }

 func BenchmarkSecretConnection(b *testing.B) {
 	b.StopTimer()
 	fooSecConn, barSecConn := makeSecretConnPair(b)
 	fooWriteText := RandStr(dataMaxSize)
 	// Consume reads from bar's reader
 	go func() {
 		readBuffer := make([]byte, dataMaxSize)
 		for {
 			_, err := barSecConn.Read(readBuffer)
 			if err == io.EOF {
 				return
 			} else if err != nil {
 				b.Fatalf("Failed to read from barSecConn: %v", err)
 			}
 		}
 	}()

 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
 		_, err := fooSecConn.Write([]byte(fooWriteText))
 		if err != nil {
 			b.Fatalf("Failed to write to fooSecConn: %v", err)
 		}
 	}
 	b.StopTimer()

 	fooSecConn.Close()
 	//barSecConn.Close() race condition
 }
--- a/switch.go
+++ b/switch.go
@ -0,0 +1,384 @@
 package p2p

 import (
 	"errors"
 	"fmt"
 	"net"
 	"time"

 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-crypto"
 	"github.com/tendermint/log15"
 )

 type Reactor interface {
 	Service // Start, Stop

 	SetSwitch(*Switch)
 	GetChannels() []*ChannelDescriptor
 	AddPeer(peer *Peer)
 	RemovePeer(peer *Peer, reason interface{})
 	Receive(chID byte, peer *Peer, msgBytes []byte)
 }

 //--------------------------------------

 type BaseReactor struct {
 	QuitService // Provides Start, Stop, .Quit
 	Switch      *Switch
 }

 func NewBaseReactor(log log15.Logger, name string, impl Reactor) *BaseReactor {
 	return &BaseReactor{
 		QuitService: *NewQuitService(log, name, impl),
 		Switch:      nil,
 	}
 }

 func (br *BaseReactor) SetSwitch(sw *Switch) {
 	br.Switch = sw
 }
 func (_ *BaseReactor) GetChannels() []*ChannelDescriptor              { return nil }
 func (_ *BaseReactor) AddPeer(peer *Peer)                             {}
 func (_ *BaseReactor) RemovePeer(peer *Peer, reason interface{})      {}
 func (_ *BaseReactor) Receive(chID byte, peer *Peer, msgBytes []byte) {}

 //-----------------------------------------------------------------------------

 /*
 The `Switch` handles peer connections and exposes an API to receive incoming messages
 on `Reactors`.  Each `Reactor` is responsible for handling incoming messages of one
 or more `Channels`.  So while sending outgoing messages is typically performed on the peer,
 incoming messages are received on the reactor.
 */
 type Switch struct {
 	BaseService

 	listeners    []Listener
 	reactors     map[string]Reactor
 	chDescs      []*ChannelDescriptor
 	reactorsByCh map[byte]Reactor
 	peers        *PeerSet
 	dialing      *CMap
 	nodeInfo     *NodeInfo             // our node info
 	nodePrivKey  crypto.PrivKeyEd25519 // our node privkey
 }

 var (
 	ErrSwitchDuplicatePeer      = errors.New("Duplicate peer")
 	ErrSwitchMaxPeersPerIPRange = errors.New("IP range has too many peers")
 )

 const (
 	peerDialTimeoutSeconds  = 3  // TODO make this configurable
 	handshakeTimeoutSeconds = 20 // TODO make this configurable
 	maxNumPeers             = 50 // TODO make this configurable
 )

 func NewSwitch() *Switch {
 	sw := &Switch{
 		reactors:     make(map[string]Reactor),
 		chDescs:      make([]*ChannelDescriptor, 0),
 		reactorsByCh: make(map[byte]Reactor),
 		peers:        NewPeerSet(),
 		dialing:      NewCMap(),
 		nodeInfo:     nil,
 	}
 	sw.BaseService = *NewBaseService(log, "P2P Switch", sw)
 	return sw
 }

 // Not goroutine safe.
 func (sw *Switch) AddReactor(name string, reactor Reactor) Reactor {
 	// Validate the reactor.
 	// No two reactors can share the same channel.
 	reactorChannels := reactor.GetChannels()
 	for _, chDesc := range reactorChannels {
 		chID := chDesc.ID
 		if sw.reactorsByCh[chID] != nil {
 			PanicSanity(fmt.Sprintf("Channel %X has multiple reactors %v & %v", chID, sw.reactorsByCh[chID], reactor))
 		}
 		sw.chDescs = append(sw.chDescs, chDesc)
 		sw.reactorsByCh[chID] = reactor
 	}
 	sw.reactors[name] = reactor
 	reactor.SetSwitch(sw)
 	return reactor
 }

 // Not goroutine safe.
 func (sw *Switch) Reactors() map[string]Reactor {
 	return sw.reactors
 }

 // Not goroutine safe.
 func (sw *Switch) Reactor(name string) Reactor {
 	return sw.reactors[name]
 }

 // Not goroutine safe.
 func (sw *Switch) AddListener(l Listener) {
 	sw.listeners = append(sw.listeners, l)
 }

 // Not goroutine safe.
 func (sw *Switch) Listeners() []Listener {
 	return sw.listeners
 }

 // Not goroutine safe.
 func (sw *Switch) IsListening() bool {
 	return len(sw.listeners) > 0
 }

 // Not goroutine safe.
 func (sw *Switch) SetNodeInfo(nodeInfo *NodeInfo) {
 	sw.nodeInfo = nodeInfo
 }

 // Not goroutine safe.
 func (sw *Switch) NodeInfo() *NodeInfo {
 	return sw.nodeInfo
 }

 // Not goroutine safe.
 // NOTE: Overwrites sw.nodeInfo.PubKey
 func (sw *Switch) SetNodePrivKey(nodePrivKey crypto.PrivKeyEd25519) {
 	sw.nodePrivKey = nodePrivKey
 	if sw.nodeInfo != nil {
 		sw.nodeInfo.PubKey = nodePrivKey.PubKey().(crypto.PubKeyEd25519)
 	}
 }

 // Switch.Start() starts all the reactors, peers, and listeners.
 func (sw *Switch) OnStart() error {
 	sw.BaseService.OnStart()
 	// Start reactors
 	for _, reactor := range sw.reactors {
 		_, err := reactor.Start()
 		if err != nil {
 			return err
 		}
 	}
 	// Start peers
 	for _, peer := range sw.peers.List() {
 		sw.startInitPeer(peer)
 	}
 	// Start listeners
 	for _, listener := range sw.listeners {
 		go sw.listenerRoutine(listener)
 	}
 	return nil
 }

 func (sw *Switch) OnStop() {
 	sw.BaseService.OnStop()
 	// Stop listeners
 	for _, listener := range sw.listeners {
 		listener.Stop()
 	}
 	sw.listeners = nil
 	// Stop peers
 	for _, peer := range sw.peers.List() {
 		peer.Stop()
 	}
 	sw.peers = NewPeerSet()
 	// Stop reactors
 	for _, reactor := range sw.reactors {
 		reactor.Stop()
 	}
 }

 // NOTE: This performs a blocking handshake before the peer is added.
 // CONTRACT: Iff error is returned, peer is nil, and conn is immediately closed.
 func (sw *Switch) AddPeerWithConnection(conn net.Conn, outbound bool) (*Peer, error) {
 	// Set deadline for handshake so we don't block forever on conn.ReadFull
 	conn.SetDeadline(time.Now().Add(handshakeTimeoutSeconds * time.Second))

 	// First, encrypt the connection.
 	sconn, err := MakeSecretConnection(conn, sw.nodePrivKey)
 	if err != nil {
 		conn.Close()
 		return nil, err
 	}
 	// Then, perform node handshake
 	peerNodeInfo, err := peerHandshake(sconn, sw.nodeInfo)
 	if err != nil {
 		sconn.Close()
 		return nil, err
 	}
 	// Check that the professed PubKey matches the sconn's.
 	if !peerNodeInfo.PubKey.Equals(sconn.RemotePubKey()) {
 		sconn.Close()
 		return nil, fmt.Errorf("Ignoring connection with unmatching pubkey: %v vs %v",
 			peerNodeInfo.PubKey, sconn.RemotePubKey())
 	}
 	// Avoid self
 	if peerNodeInfo.PubKey.Equals(sw.nodeInfo.PubKey) {
 		sconn.Close()
 		return nil, fmt.Errorf("Ignoring connection from self")
 	}
 	// Check version, chain id
 	if err := sw.nodeInfo.CompatibleWith(peerNodeInfo); err != nil {
 		sconn.Close()
 		return nil, err
 	}

 	// The peerNodeInfo is not verified, so overwrite
 	// the IP, and the port too if we dialed out
 	// Everything else we just have to trust
 	peerNodeInfo.Address = sconn.RemoteAddr().String()
 	peer := newPeer(sconn, peerNodeInfo, outbound, sw.reactorsByCh, sw.chDescs, sw.StopPeerForError)

 	// Add the peer to .peers
 	// ignore if duplicate or if we already have too many for that IP range
 	if err := sw.peers.Add(peer); err != nil {
 		log.Notice("Ignoring peer", "error", err, "peer", peer)
 		peer.Stop()
 		return nil, err
 	}

 	// remove deadline and start peer
 	conn.SetDeadline(time.Time{})
 	if sw.IsRunning() {
 		sw.startInitPeer(peer)
 	}

 	log.Notice("Added peer", "peer", peer)
 	return peer, nil
 }

 func (sw *Switch) startInitPeer(peer *Peer) {
 	peer.Start()               // spawn send/recv routines
 	sw.addPeerToReactors(peer) // run AddPeer on each reactor
 }

 func (sw *Switch) DialPeerWithAddress(addr *NetAddress) (*Peer, error) {
 	log.Info("Dialing address", "address", addr)
 	sw.dialing.Set(addr.IP.String(), addr)
 	conn, err := addr.DialTimeout(peerDialTimeoutSeconds * time.Second)
 	sw.dialing.Delete(addr.IP.String())
 	if err != nil {
 		log.Info("Failed dialing address", "address", addr, "error", err)
 		return nil, err
 	}
 	peer, err := sw.AddPeerWithConnection(conn, true)
 	if err != nil {
 		log.Info("Failed adding peer", "address", addr, "conn", conn, "error", err)
 		return nil, err
 	}
 	log.Notice("Dialed and added peer", "address", addr, "peer", peer)
 	return peer, nil
 }

 func (sw *Switch) IsDialing(addr *NetAddress) bool {
 	return sw.dialing.Has(addr.IP.String())
 }

 // Broadcast runs a go routine for each attempted send, which will block
 // trying to send for defaultSendTimeoutSeconds. Returns a channel
 // which receives success values for each attempted send (false if times out)
 func (sw *Switch) Broadcast(chID byte, msg interface{}) chan bool {
 	successChan := make(chan bool, len(sw.peers.List()))
 	log.Info("Broadcast", "channel", chID, "msg", msg)
 	for _, peer := range sw.peers.List() {
 		go func(peer *Peer) {
 			success := peer.Send(chID, msg)
 			successChan <- success
 		}(peer)
 	}
 	return successChan
 }

 // Returns the count of outbound/inbound and outbound-dialing peers.
 func (sw *Switch) NumPeers() (outbound, inbound, dialing int) {
 	peers := sw.peers.List()
 	for _, peer := range peers {
 		if peer.outbound {
 			outbound++
 		} else {
 			inbound++
 		}
 	}
 	dialing = sw.dialing.Size()
 	return
 }

 func (sw *Switch) Peers() IPeerSet {
 	return sw.peers
 }

 // Disconnect from a peer due to external error.
 // TODO: make record depending on reason.
 func (sw *Switch) StopPeerForError(peer *Peer, reason interface{}) {
 	log.Notice("Stopping peer for error", "peer", peer, "error", reason)
 	sw.peers.Remove(peer)
 	peer.Stop()
 	sw.removePeerFromReactors(peer, reason)
 }

 // Disconnect from a peer gracefully.
 // TODO: handle graceful disconnects.
 func (sw *Switch) StopPeerGracefully(peer *Peer) {
 	log.Notice("Stopping peer gracefully")
 	sw.peers.Remove(peer)
 	peer.Stop()
 	sw.removePeerFromReactors(peer, nil)
 }

 func (sw *Switch) addPeerToReactors(peer *Peer) {
 	for _, reactor := range sw.reactors {
 		reactor.AddPeer(peer)
 	}
 }

 func (sw *Switch) removePeerFromReactors(peer *Peer, reason interface{}) {
 	for _, reactor := range sw.reactors {
 		reactor.RemovePeer(peer, reason)
 	}
 }

 func (sw *Switch) listenerRoutine(l Listener) {
 	for {
 		inConn, ok := <-l.Connections()
 		if !ok {
 			break
 		}

 		// ignore connection if we already have enough
 		if maxNumPeers <= sw.peers.Size() {
 			log.Info("Ignoring inbound connection: already have enough peers", "address", inConn.RemoteAddr().String(), "numPeers", sw.peers.Size(), "max", maxNumPeers)
 			continue
 		}

 		// Ignore connections from IP ranges for which we have too many
 		if sw.peers.HasMaxForIPRange(inConn) {
 			log.Info("Ignoring inbound connection: already have enough peers for that IP range", "address", inConn.RemoteAddr().String())
 			continue
 		}

 		// New inbound connection!
 		_, err := sw.AddPeerWithConnection(inConn, false)
 		if err != nil {
 			log.Notice("Ignoring inbound connection: error on AddPeerWithConnection", "address", inConn.RemoteAddr().String(), "error", err)
 			continue
 		}

 		// NOTE: We don't yet have the listening port of the
 		// remote (if they have a listener at all).
 		// The peerHandshake will handle that
 	}

 	// cleanup
 }

 //-----------------------------------------------------------------------------

 type SwitchEventNewPeer struct {
 	Peer *Peer
 }

 type SwitchEventDonePeer struct {
 	Peer  *Peer
 	Error interface{}
 }
--- a/switch_test.go
+++ b/switch_test.go
@ -0,0 +1,234 @@
 package p2p

 import (
 	"bytes"
 	"sync"
 	"testing"
 	"time"

 	. "github.com/tendermint/go-common"
 	"github.com/tendermint/go-crypto"
 	"github.com/tendermint/go-wire"
 )

 type PeerMessage struct {
 	PeerKey string
 	Bytes   []byte
 	Counter int
 }

 type TestReactor struct {
 	BaseReactor

 	mtx          sync.Mutex
 	channels     []*ChannelDescriptor
 	peersAdded   []*Peer
 	peersRemoved []*Peer
 	logMessages  bool
 	msgsCounter  int
 	msgsReceived map[byte][]PeerMessage
 }

 func NewTestReactor(channels []*ChannelDescriptor, logMessages bool) *TestReactor {
 	tr := &TestReactor{
 		channels:     channels,
 		logMessages:  logMessages,
 		msgsReceived: make(map[byte][]PeerMessage),
 	}
 	tr.BaseReactor = *NewBaseReactor(log, "TestReactor", tr)
 	return tr
 }

 func (tr *TestReactor) GetChannels() []*ChannelDescriptor {
 	return tr.channels
 }

 func (tr *TestReactor) AddPeer(peer *Peer) {
 	tr.mtx.Lock()
 	defer tr.mtx.Unlock()
 	tr.peersAdded = append(tr.peersAdded, peer)
 }

 func (tr *TestReactor) RemovePeer(peer *Peer, reason interface{}) {
 	tr.mtx.Lock()
 	defer tr.mtx.Unlock()
 	tr.peersRemoved = append(tr.peersRemoved, peer)
 }

 func (tr *TestReactor) Receive(chID byte, peer *Peer, msgBytes []byte) {
 	if tr.logMessages {
 		tr.mtx.Lock()
 		defer tr.mtx.Unlock()
 		//fmt.Printf("Received: %X, %X\n", chID, msgBytes)
 		tr.msgsReceived[chID] = append(tr.msgsReceived[chID], PeerMessage{peer.Key, msgBytes, tr.msgsCounter})
 		tr.msgsCounter++
 	}
 }

 //-----------------------------------------------------------------------------

 // convenience method for creating two switches connected to each other.
 func makeSwitchPair(t testing.TB, initSwitch func(*Switch) *Switch) (*Switch, *Switch) {

 	s1PrivKey := crypto.GenPrivKeyEd25519()
 	s2PrivKey := crypto.GenPrivKeyEd25519()

 	// Create two switches that will be interconnected.
 	s1 := initSwitch(NewSwitch())
 	s1.SetNodeInfo(&NodeInfo{
 		PubKey:  s1PrivKey.PubKey().(crypto.PubKeyEd25519),
 		Moniker: "switch1",
 		Network: "testing",
 		Version: "123.123.123",
 	})
 	s1.SetNodePrivKey(s1PrivKey)
 	s2 := initSwitch(NewSwitch())
 	s2.SetNodeInfo(&NodeInfo{
 		PubKey:  s2PrivKey.PubKey().(crypto.PubKeyEd25519),
 		Moniker: "switch2",
 		Network: "testing",
 		Version: "123.123.123",
 	})
 	s2.SetNodePrivKey(s2PrivKey)

 	// Start switches and reactors
 	s1.Start()
 	s2.Start()

 	// Create a listener for s1
 	l := NewDefaultListener("tcp", ":8001", true)

 	// Dial the listener & add the connection to s2.
 	lAddr := l.ExternalAddress()
 	connOut, err := lAddr.Dial()
 	if err != nil {
 		t.Fatalf("Could not connect to listener address %v", lAddr)
 	} else {
 		t.Logf("Created a connection to listener address %v", lAddr)
 	}
 	connIn, ok := <-l.Connections()
 	if !ok {
 		t.Fatalf("Could not get inbound connection from listener")
 	}

 	go s1.AddPeerWithConnection(connIn, false) // AddPeer is blocking, requires handshake.
 	s2.AddPeerWithConnection(connOut, true)

 	// Wait for things to happen, peers to get added...
 	time.Sleep(100 * time.Millisecond)

 	// Close the server, no longer needed.
 	l.Stop()

 	return s1, s2
 }

 func TestSwitches(t *testing.T) {
 	s1, s2 := makeSwitchPair(t, func(sw *Switch) *Switch {
 		// Make two reactors of two channels each
 		sw.AddReactor("foo", NewTestReactor([]*ChannelDescriptor{
 			&ChannelDescriptor{ID: byte(0x00), Priority: 10},
 			&ChannelDescriptor{ID: byte(0x01), Priority: 10},
 		}, true))
 		sw.AddReactor("bar", NewTestReactor([]*ChannelDescriptor{
 			&ChannelDescriptor{ID: byte(0x02), Priority: 10},
 			&ChannelDescriptor{ID: byte(0x03), Priority: 10},
 		}, true))
 		return sw
 	})
 	defer s1.Stop()
 	defer s2.Stop()

 	// Lets send a message from s1 to s2.
 	if s1.Peers().Size() != 1 {
 		t.Errorf("Expected exactly 1 peer in s1, got %v", s1.Peers().Size())
 	}
 	if s2.Peers().Size() != 1 {
 		t.Errorf("Expected exactly 1 peer in s2, got %v", s2.Peers().Size())
 	}

 	ch0Msg := "channel zero"
 	ch1Msg := "channel foo"
 	ch2Msg := "channel bar"

 	s1.Broadcast(byte(0x00), ch0Msg)
 	s1.Broadcast(byte(0x01), ch1Msg)
 	s1.Broadcast(byte(0x02), ch2Msg)

 	// Wait for things to settle...
 	time.Sleep(5000 * time.Millisecond)

 	// Check message on ch0
 	ch0Msgs := s2.Reactor("foo").(*TestReactor).msgsReceived[byte(0x00)]
 	if len(ch0Msgs) != 1 {
 		t.Errorf("Expected to have received 1 message in ch0")
 	}
 	if !bytes.Equal(ch0Msgs[0].Bytes, wire.BinaryBytes(ch0Msg)) {
 		t.Errorf("Unexpected message bytes. Wanted: %X, Got: %X", wire.BinaryBytes(ch0Msg), ch0Msgs[0].Bytes)
 	}

 	// Check message on ch1
 	ch1Msgs := s2.Reactor("foo").(*TestReactor).msgsReceived[byte(0x01)]
 	if len(ch1Msgs) != 1 {
 		t.Errorf("Expected to have received 1 message in ch1")
 	}
 	if !bytes.Equal(ch1Msgs[0].Bytes, wire.BinaryBytes(ch1Msg)) {
 		t.Errorf("Unexpected message bytes. Wanted: %X, Got: %X", wire.BinaryBytes(ch1Msg), ch1Msgs[0].Bytes)
 	}

 	// Check message on ch2
 	ch2Msgs := s2.Reactor("bar").(*TestReactor).msgsReceived[byte(0x02)]
 	if len(ch2Msgs) != 1 {
 		t.Errorf("Expected to have received 1 message in ch2")
 	}
 	if !bytes.Equal(ch2Msgs[0].Bytes, wire.BinaryBytes(ch2Msg)) {
 		t.Errorf("Unexpected message bytes. Wanted: %X, Got: %X", wire.BinaryBytes(ch2Msg), ch2Msgs[0].Bytes)
 	}

 }

 func BenchmarkSwitches(b *testing.B) {

 	b.StopTimer()

 	s1, s2 := makeSwitchPair(b, func(sw *Switch) *Switch {
 		// Make bar reactors of bar channels each
 		sw.AddReactor("foo", NewTestReactor([]*ChannelDescriptor{
 			&ChannelDescriptor{ID: byte(0x00), Priority: 10},
 			&ChannelDescriptor{ID: byte(0x01), Priority: 10},
 		}, false))
 		sw.AddReactor("bar", NewTestReactor([]*ChannelDescriptor{
 			&ChannelDescriptor{ID: byte(0x02), Priority: 10},
 			&ChannelDescriptor{ID: byte(0x03), Priority: 10},
 		}, false))
 		return sw
 	})
 	defer s1.Stop()
 	defer s2.Stop()

 	// Allow time for goroutines to boot up
 	time.Sleep(1000 * time.Millisecond)
 	b.StartTimer()

 	numSuccess, numFailure := 0, 0

 	// Send random message from foo channel to another
 	for i := 0; i < b.N; i++ {
 		chID := byte(i % 4)
 		successChan := s1.Broadcast(chID, "test data")
 		for s := range successChan {
 			if s {
 				numSuccess += 1
 			} else {
 				numFailure += 1
 			}
 		}
 	}

 	log.Warn(Fmt("success: %v, failure: %v", numSuccess, numFailure))

 	// Allow everything to flush before stopping switches & closing connections.
 	b.StopTimer()
 	time.Sleep(1000 * time.Millisecond)

 }
--- a/types.go
+++ b/types.go
@ -0,0 +1,74 @@
 package p2p

 import (
 	"fmt"
 	"net"
 	"strconv"
 	"strings"

 	"github.com/tendermint/go-crypto"
 )

 type NodeInfo struct {
 	PubKey  crypto.PubKeyEd25519 `json:"pub_key"`
 	Moniker string               `json:"moniker"`
 	Network string               `json:"network"`
 	Address string               `json:"address"`
 	Version string               `json:"version"` // major.minor.revision
 	Other   []string             `json:"other"`   // other application specific data
 }

 // CONTRACT: two nodes are compactible if the major/minor versions match and network match
 func (info *NodeInfo) CompatibleWith(other *NodeInfo) error {
 	iMajor, iMinor, _, iErr := splitVersion(info.Version)
 	oMajor, oMinor, _, oErr := splitVersion(other.Version)

 	// if our own version number is not formatted right, we messed up
 	if iErr != nil {
 		return iErr
 	}

 	// version number must be formatted correctly ("x.x.x")
 	if oErr != nil {
 		return oErr
 	}

 	// major version must match
 	if iMajor != oMajor {
 		return fmt.Errorf("Peer is on a different major version. Got %v, expected %v", oMajor, iMajor)
 	}

 	// minor version must match
 	if iMinor != oMinor {
 		return fmt.Errorf("Peer is on a different minor version. Got %v, expected %v", oMinor, iMinor)
 	}

 	// nodes must be on the same network
 	if info.Network != other.Network {
 		return fmt.Errorf("Peer is on a different network. Got %v, expected %v", other.Network, info.Network)
 	}

 	return nil
 }

 func (info *NodeInfo) Host() string {
 	host, _, _ := net.SplitHostPort(info.Address)
 	return host
 }

 func (info *NodeInfo) Port() int {
 	_, port, _ := net.SplitHostPort(info.Address)
 	port_i, err := strconv.Atoi(port)
 	if err != nil {
 		return -1
 	}
 	return port_i
 }

 func splitVersion(version string) (string, string, string, error) {
 	spl := strings.Split(version, ".")
 	if len(spl) != 3 {
 		return "", "", "", fmt.Errorf("Invalid version format %v", version)
 	}
 	return spl[0], spl[1], spl[2], nil
 }
--- a/upnp/README.md
+++ b/upnp/README.md
@ -0,0 +1,5 @@
 # `tendermint/p2p/upnp`

 ## Resources

 * http://www.upnp-hacks.org/upnp.html
--- a/upnp/log.go
+++ b/upnp/log.go
@ -0,0 +1,7 @@
 package upnp

 import (
 	"github.com/tendermint/go-logger"
 )

 var log = logger.New("module", "upnp")
--- a/upnp/probe.go
+++ b/upnp/probe.go
@ -0,0 +1,111 @@
 package upnp

 import (
 	"errors"
 	"fmt"
 	"net"
 	"time"

 	. "github.com/tendermint/go-common"
 )

 type UPNPCapabilities struct {
 	PortMapping bool
 	Hairpin     bool
 }

 func makeUPNPListener(intPort int, extPort int) (NAT, net.Listener, net.IP, error) {
 	nat, err := Discover()
 	if err != nil {
 		return nil, nil, nil, errors.New(fmt.Sprintf("NAT upnp could not be discovered: %v", err))
 	}
 	log.Info(Fmt("ourIP: %v", nat.(*upnpNAT).ourIP))

 	ext, err := nat.GetExternalAddress()
 	if err != nil {
 		return nat, nil, nil, errors.New(fmt.Sprintf("External address error: %v", err))
 	}
 	log.Info(Fmt("External address: %v", ext))

 	port, err := nat.AddPortMapping("tcp", extPort, intPort, "Tendermint UPnP Probe", 0)
 	if err != nil {
 		return nat, nil, ext, errors.New(fmt.Sprintf("Port mapping error: %v", err))
 	}
 	log.Info(Fmt("Port mapping mapped: %v", port))

 	// also run the listener, open for all remote addresses.
 	listener, err := net.Listen("tcp", fmt.Sprintf(":%v", intPort))
 	if err != nil {
 		return nat, nil, ext, errors.New(fmt.Sprintf("Error establishing listener: %v", err))
 	}
 	return nat, listener, ext, nil
 }

 func testHairpin(listener net.Listener, extAddr string) (supportsHairpin bool) {
 	// Listener
 	go func() {
 		inConn, err := listener.Accept()
 		if err != nil {
 			log.Notice(Fmt("Listener.Accept() error: %v", err))
 			return
 		}
 		log.Info(Fmt("Accepted incoming connection: %v -> %v", inConn.LocalAddr(), inConn.RemoteAddr()))
 		buf := make([]byte, 1024)
 		n, err := inConn.Read(buf)
 		if err != nil {
 			log.Notice(Fmt("Incoming connection read error: %v", err))
 			return
 		}
 		log.Info(Fmt("Incoming connection read %v bytes: %X", n, buf))
 		if string(buf) == "test data" {
 			supportsHairpin = true
 			return
 		}
 	}()

 	// Establish outgoing
 	outConn, err := net.Dial("tcp", extAddr)
 	if err != nil {
 		log.Notice(Fmt("Outgoing connection dial error: %v", err))
 		return
 	}

 	n, err := outConn.Write([]byte("test data"))
 	if err != nil {
 		log.Notice(Fmt("Outgoing connection write error: %v", err))
 		return
 	}
 	log.Info(Fmt("Outgoing connection wrote %v bytes", n))

 	// Wait for data receipt
 	time.Sleep(1 * time.Second)
 	return
 }

 func Probe() (caps UPNPCapabilities, err error) {
 	log.Info("Probing for UPnP!")

 	intPort, extPort := 8001, 8001

 	nat, listener, ext, err := makeUPNPListener(intPort, extPort)
 	if err != nil {
 		return
 	}
 	caps.PortMapping = true

 	// Deferred cleanup
 	defer func() {
 		err = nat.DeletePortMapping("tcp", intPort, extPort)
 		if err != nil {
 			log.Warn(Fmt("Port mapping delete error: %v", err))
 		}
 		listener.Close()
 	}()

 	supportsHairpin := testHairpin(listener, fmt.Sprintf("%v:%v", ext, extPort))
 	if supportsHairpin {
 		caps.Hairpin = true
 	}

 	return
 }
--- a/upnp/upnp.go
+++ b/upnp/upnp.go
@ -0,0 +1,380 @@
 /*
 Taken from taipei-torrent

 Just enough UPnP to be able to forward ports
 */
 package upnp

 // BUG(jae): TODO: use syscalls to get actual ourIP. http://pastebin.com/9exZG4rh

 import (
 	"bytes"
 	"encoding/xml"
 	"errors"
 	"io/ioutil"
 	"net"
 	"net/http"
 	"strconv"
 	"strings"
 	"time"
 )

 type upnpNAT struct {
 	serviceURL string
 	ourIP      string
 	urnDomain  string
 }

 // protocol is either "udp" or "tcp"
 type NAT interface {
 	GetExternalAddress() (addr net.IP, err error)
 	AddPortMapping(protocol string, externalPort, internalPort int, description string, timeout int) (mappedExternalPort int, err error)
 	DeletePortMapping(protocol string, externalPort, internalPort int) (err error)
 }

 func Discover() (nat NAT, err error) {
 	ssdp, err := net.ResolveUDPAddr("udp4", "239.255.255.250:1900")
 	if err != nil {
 		return
 	}
 	conn, err := net.ListenPacket("udp4", ":0")
 	if err != nil {
 		return
 	}
 	socket := conn.(*net.UDPConn)
 	defer socket.Close()

 	err = socket.SetDeadline(time.Now().Add(3 * time.Second))
 	if err != nil {
 		return
 	}

 	st := "InternetGatewayDevice:1"

 	buf := bytes.NewBufferString(
 		"M-SEARCH * HTTP/1.1\r\n" +
 			"HOST: 239.255.255.250:1900\r\n" +
 			"ST: ssdp:all\r\n" +
 			"MAN: \"ssdp:discover\"\r\n" +
 			"MX: 2\r\n\r\n")
 	message := buf.Bytes()
 	answerBytes := make([]byte, 1024)
 	for i := 0; i < 3; i++ {
 		_, err = socket.WriteToUDP(message, ssdp)
 		if err != nil {
 			return
 		}
 		var n int
 		n, _, err = socket.ReadFromUDP(answerBytes)
 		for {
 			n, _, err = socket.ReadFromUDP(answerBytes)
 			if err != nil {
 				break
 			}
 			answer := string(answerBytes[0:n])
 			if strings.Index(answer, st) < 0 {
 				continue
 			}
 			// HTTP header field names are case-insensitive.
 			// http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2
 			locString := "\r\nlocation:"
 			answer = strings.ToLower(answer)
 			locIndex := strings.Index(answer, locString)
 			if locIndex < 0 {
 				continue
 			}
 			loc := answer[locIndex+len(locString):]
 			endIndex := strings.Index(loc, "\r\n")
 			if endIndex < 0 {
 				continue
 			}
 			locURL := strings.TrimSpace(loc[0:endIndex])
 			var serviceURL, urnDomain string
 			serviceURL, urnDomain, err = getServiceURL(locURL)
 			if err != nil {
 				return
 			}
 			var ourIP net.IP
 			ourIP, err = localIPv4()
 			if err != nil {
 				return
 			}
 			nat = &upnpNAT{serviceURL: serviceURL, ourIP: ourIP.String(), urnDomain: urnDomain}
 			return
 		}
 	}
 	err = errors.New("UPnP port discovery failed.")
 	return
 }

 type Envelope struct {
 	XMLName xml.Name `xml:"http://schemas.xmlsoap.org/soap/envelope/ Envelope"`
 	Soap    *SoapBody
 }
 type SoapBody struct {
 	XMLName    xml.Name `xml:"http://schemas.xmlsoap.org/soap/envelope/ Body"`
 	ExternalIP *ExternalIPAddressResponse
 }

 type ExternalIPAddressResponse struct {
 	XMLName   xml.Name `xml:"GetExternalIPAddressResponse"`
 	IPAddress string   `xml:"NewExternalIPAddress"`
 }

 type ExternalIPAddress struct {
 	XMLName xml.Name `xml:"NewExternalIPAddress"`
 	IP      string
 }

 type UPNPService struct {
 	ServiceType string `xml:"serviceType"`
 	ControlURL  string `xml:"controlURL"`
 }

 type DeviceList struct {
 	Device []Device `xml:"device"`
 }

 type ServiceList struct {
 	Service []UPNPService `xml:"service"`
 }

 type Device struct {
 	XMLName     xml.Name    `xml:"device"`
 	DeviceType  string      `xml:"deviceType"`
 	DeviceList  DeviceList  `xml:"deviceList"`
 	ServiceList ServiceList `xml:"serviceList"`
 }

 type Root struct {
 	Device Device
 }

 func getChildDevice(d *Device, deviceType string) *Device {
 	dl := d.DeviceList.Device
 	for i := 0; i < len(dl); i++ {
 		if strings.Index(dl[i].DeviceType, deviceType) >= 0 {
 			return &dl[i]
 		}
 	}
 	return nil
 }

 func getChildService(d *Device, serviceType string) *UPNPService {
 	sl := d.ServiceList.Service
 	for i := 0; i < len(sl); i++ {
 		if strings.Index(sl[i].ServiceType, serviceType) >= 0 {
 			return &sl[i]
 		}
 	}
 	return nil
 }

 func localIPv4() (net.IP, error) {
 	tt, err := net.Interfaces()
 	if err != nil {
 		return nil, err
 	}
 	for _, t := range tt {
 		aa, err := t.Addrs()
 		if err != nil {
 			return nil, err
 		}
 		for _, a := range aa {
 			ipnet, ok := a.(*net.IPNet)
 			if !ok {
 				continue
 			}
 			v4 := ipnet.IP.To4()
 			if v4 == nil || v4[0] == 127 { // loopback address
 				continue
 			}
 			return v4, nil
 		}
 	}
 	return nil, errors.New("cannot find local IP address")
 }

 func getServiceURL(rootURL string) (url, urnDomain string, err error) {
 	r, err := http.Get(rootURL)
 	if err != nil {
 		return
 	}
 	defer r.Body.Close()
 	if r.StatusCode >= 400 {
 		err = errors.New(string(r.StatusCode))
 		return
 	}
 	var root Root
 	err = xml.NewDecoder(r.Body).Decode(&root)
 	if err != nil {
 		return
 	}
 	a := &root.Device
 	if strings.Index(a.DeviceType, "InternetGatewayDevice:1") < 0 {
 		err = errors.New("No InternetGatewayDevice")
 		return
 	}
 	b := getChildDevice(a, "WANDevice:1")
 	if b == nil {
 		err = errors.New("No WANDevice")
 		return
 	}
 	c := getChildDevice(b, "WANConnectionDevice:1")
 	if c == nil {
 		err = errors.New("No WANConnectionDevice")
 		return
 	}
 	d := getChildService(c, "WANIPConnection:1")
 	if d == nil {
 		// Some routers don't follow the UPnP spec, and put WanIPConnection under WanDevice,
 		// instead of under WanConnectionDevice
 		d = getChildService(b, "WANIPConnection:1")

 		if d == nil {
 			err = errors.New("No WANIPConnection")
 			return
 		}
 	}
 	// Extract the domain name, which isn't always 'schemas-upnp-org'
 	urnDomain = strings.Split(d.ServiceType, ":")[1]
 	url = combineURL(rootURL, d.ControlURL)
 	return
 }

 func combineURL(rootURL, subURL string) string {
 	protocolEnd := "://"
 	protoEndIndex := strings.Index(rootURL, protocolEnd)
 	a := rootURL[protoEndIndex+len(protocolEnd):]
 	rootIndex := strings.Index(a, "/")
 	return rootURL[0:protoEndIndex+len(protocolEnd)+rootIndex] + subURL
 }

 func soapRequest(url, function, message, domain string) (r *http.Response, err error) {
 	fullMessage := "<?xml version=\"1.0\" ?>" +
 		"<s:Envelope xmlns:s=\"http://schemas.xmlsoap.org/soap/envelope/\" s:encodingStyle=\"http://schemas.xmlsoap.org/soap/encoding/\">\r\n" +
 		"<s:Body>" + message + "</s:Body></s:Envelope>"

 	req, err := http.NewRequest("POST", url, strings.NewReader(fullMessage))
 	if err != nil {
 		return nil, err
 	}
 	req.Header.Set("Content-Type", "text/xml ; charset=\"utf-8\"")
 	req.Header.Set("User-Agent", "Darwin/10.0.0, UPnP/1.0, MiniUPnPc/1.3")
 	//req.Header.Set("Transfer-Encoding", "chunked")
 	req.Header.Set("SOAPAction", "\"urn:"+domain+":service:WANIPConnection:1#"+function+"\"")
 	req.Header.Set("Connection", "Close")
 	req.Header.Set("Cache-Control", "no-cache")
 	req.Header.Set("Pragma", "no-cache")

 	// log.Stderr("soapRequest ", req)

 	r, err = http.DefaultClient.Do(req)
 	if err != nil {
 		return nil, err
 	}
 	/*if r.Body != nil {
 	    defer r.Body.Close()
 	}*/

 	if r.StatusCode >= 400 {
 		// log.Stderr(function, r.StatusCode)
 		err = errors.New("Error " + strconv.Itoa(r.StatusCode) + " for " + function)
 		r = nil
 		return
 	}
 	return
 }

 type statusInfo struct {
 	externalIpAddress string
 }

 func (n *upnpNAT) getExternalIPAddress() (info statusInfo, err error) {

 	message := "<u:GetExternalIPAddress xmlns:u=\"urn:" + n.urnDomain + ":service:WANIPConnection:1\">\r\n" +
 		"</u:GetExternalIPAddress>"

 	var response *http.Response
 	response, err = soapRequest(n.serviceURL, "GetExternalIPAddress", message, n.urnDomain)
 	if response != nil {
 		defer response.Body.Close()
 	}
 	if err != nil {
 		return
 	}
 	var envelope Envelope
 	data, err := ioutil.ReadAll(response.Body)
 	reader := bytes.NewReader(data)
 	xml.NewDecoder(reader).Decode(&envelope)

 	info = statusInfo{envelope.Soap.ExternalIP.IPAddress}

 	if err != nil {
 		return
 	}

 	return
 }

 func (n *upnpNAT) GetExternalAddress() (addr net.IP, err error) {
 	info, err := n.getExternalIPAddress()
 	if err != nil {
 		return
 	}
 	addr = net.ParseIP(info.externalIpAddress)
 	return
 }

 func (n *upnpNAT) AddPortMapping(protocol string, externalPort, internalPort int, description string, timeout int) (mappedExternalPort int, err error) {
 	// A single concatenation would break ARM compilation.
 	message := "<u:AddPortMapping xmlns:u=\"urn:" + n.urnDomain + ":service:WANIPConnection:1\">\r\n" +
 		"<NewRemoteHost></NewRemoteHost><NewExternalPort>" + strconv.Itoa(externalPort)
 	message += "</NewExternalPort><NewProtocol>" + protocol + "</NewProtocol>"
 	message += "<NewInternalPort>" + strconv.Itoa(internalPort) + "</NewInternalPort>" +
 		"<NewInternalClient>" + n.ourIP + "</NewInternalClient>" +
 		"<NewEnabled>1</NewEnabled><NewPortMappingDescription>"
 	message += description +
 		"</NewPortMappingDescription><NewLeaseDuration>" + strconv.Itoa(timeout) +
 		"</NewLeaseDuration></u:AddPortMapping>"

 	var response *http.Response
 	response, err = soapRequest(n.serviceURL, "AddPortMapping", message, n.urnDomain)
 	if response != nil {
 		defer response.Body.Close()
 	}
 	if err != nil {
 		return
 	}

 	// TODO: check response to see if the port was forwarded
 	// log.Println(message, response)
 	// JAE:
 	// body, err := ioutil.ReadAll(response.Body)
 	// fmt.Println(string(body), err)
 	mappedExternalPort = externalPort
 	_ = response
 	return
 }

 func (n *upnpNAT) DeletePortMapping(protocol string, externalPort, internalPort int) (err error) {

 	message := "<u:DeletePortMapping xmlns:u=\"urn:" + n.urnDomain + ":service:WANIPConnection:1\">\r\n" +
 		"<NewRemoteHost></NewRemoteHost><NewExternalPort>" + strconv.Itoa(externalPort) +
 		"</NewExternalPort><NewProtocol>" + protocol + "</NewProtocol>" +
 		"</u:DeletePortMapping>"

 	var response *http.Response
 	response, err = soapRequest(n.serviceURL, "DeletePortMapping", message, n.urnDomain)
 	if response != nil {
 		defer response.Body.Close()
 	}
 	if err != nil {
 		return
 	}

 	// TODO: check response to see if the port was deleted
 	// log.Println(message, response)
 	_ = response
 	return
 }
--- a/util.go
+++ b/util.go
@ -0,0 +1,15 @@
 package p2p

 import (
 	"crypto/sha256"
 )

 // doubleSha256 calculates sha256(sha256(b)) and returns the resulting bytes.
 func doubleSha256(b []byte) []byte {
 	hasher := sha256.New()
 	hasher.Write(b)
 	sum := hasher.Sum(nil)
 	hasher.Reset()
 	hasher.Write(sum)
 	return hasher.Sum(nil)
 }
--- a/version.go
+++ b/version.go
@ -0,0 +1,3 @@
 package p2p

 const Version = "0.3.0"