# Using ABCI-CLI To facilitate testing and debugging of ABCI servers and simple apps, we built a CLI, the `abci-cli`, for sending ABCI messages from the command line. ## Install Make sure you [have Go installed](https://golang.org/doc/install). Next, install the `abci-cli` tool and example applications: ``` mkdir -p $GOPATH/src/github.com/tendermint cd $GOPATH/src/github.com/tendermint git clone https://github.com/tendermint/tendermint.git cd tendermint make get_tools make get_vendor_deps make install_abci ``` Now run `abci-cli` to see the list of commands: ``` Usage: abci-cli [command] Available Commands: batch Run a batch of abci commands against an application check_tx Validate a tx commit Commit the application state and return the Merkle root hash console Start an interactive abci console for multiple commands counter ABCI demo example deliver_tx Deliver a new tx to the application kvstore ABCI demo example echo Have the application echo a message help Help about any command info Get some info about the application query Query the application state set_option Set an options on the application Flags: --abci string socket or grpc (default "socket") --address string address of application socket (default "tcp://127.0.0.1:26658") -h, --help help for abci-cli -v, --verbose print the command and results as if it were a console session Use "abci-cli [command] --help" for more information about a command. ``` ## KVStore - First Example The `abci-cli` tool lets us send ABCI messages to our application, to help build and debug them. The most important messages are `deliver_tx`, `check_tx`, and `commit`, but there are others for convenience, configuration, and information purposes. We'll start a kvstore application, which was installed at the same time as `abci-cli` above. The kvstore just stores transactions in a merkle tree. Its code can be found [here](https://github.com/tendermint/tendermint/blob/develop/abci/cmd/abci-cli/abci-cli.go) and looks like: ``` func cmdKVStore(cmd *cobra.Command, args []string) error { logger := log.NewTMLogger(log.NewSyncWriter(os.Stdout)) // Create the application - in memory or persisted to disk var app types.Application if flagPersist == "" { app = kvstore.NewKVStoreApplication() } else { app = kvstore.NewPersistentKVStoreApplication(flagPersist) app.(*kvstore.PersistentKVStoreApplication).SetLogger(logger.With("module", "kvstore")) } // Start the listener srv, err := server.NewServer(flagAddrD, flagAbci, app) if err != nil { return err } srv.SetLogger(logger.With("module", "abci-server")) if err := srv.Start(); err != nil { return err } // Wait forever cmn.TrapSignal(func() { // Cleanup srv.Stop() }) return nil } ``` Start by running: ``` abci-cli kvstore ``` And in another terminal, run ``` abci-cli echo hello abci-cli info ``` You'll see something like: ``` -> data: hello -> data.hex: 68656C6C6F ``` and: ``` -> data: {"size":0} -> data.hex: 7B2273697A65223A307D ``` An ABCI application must provide two things: - a socket server - a handler for ABCI messages When we run the `abci-cli` tool we open a new connection to the application's socket server, send the given ABCI message, and wait for a response. The server may be generic for a particular language, and we provide a [reference implementation in Golang](https://github.com/tendermint/tendermint/tree/develop/abci/server). See the [list of other ABCI implementations](./ecosystem.md) for servers in other languages. The handler is specific to the application, and may be arbitrary, so long as it is deterministic and conforms to the ABCI interface specification. So when we run `abci-cli info`, we open a new connection to the ABCI server, which calls the `Info()` method on the application, which tells us the number of transactions in our Merkle tree. Now, since every command opens a new connection, we provide the `abci-cli console` and `abci-cli batch` commands, to allow multiple ABCI messages to be sent over a single connection. Running `abci-cli console` should drop you in an interactive console for speaking ABCI messages to your application. Try running these commands: ``` > echo hello -> code: OK -> data: hello -> data.hex: 0x68656C6C6F > info -> code: OK -> data: {"size":0} -> data.hex: 0x7B2273697A65223A307D > commit -> code: OK -> data.hex: 0x0000000000000000 > deliver_tx "abc" -> code: OK > info -> code: OK -> data: {"size":1} -> data.hex: 0x7B2273697A65223A317D > commit -> code: OK -> data.hex: 0x0200000000000000 > query "abc" -> code: OK -> log: exists -> height: 0 -> value: abc -> value.hex: 616263 > deliver_tx "def=xyz" -> code: OK > commit -> code: OK -> data.hex: 0x0400000000000000 > query "def" -> code: OK -> log: exists -> height: 0 -> value: xyz -> value.hex: 78797A ``` Note that if we do `deliver_tx "abc"` it will store `(abc, abc)`, but if we do `deliver_tx "abc=efg"` it will store `(abc, efg)`. Similarly, you could put the commands in a file and run `abci-cli --verbose batch < myfile`. ## Counter - Another Example Now that we've got the hang of it, let's try another application, the "counter" app. Like the kvstore app, its code can be found [here](https://github.com/tendermint/tendermint/blob/master/abci/cmd/abci-cli/abci-cli.go) and looks like: ``` func cmdCounter(cmd *cobra.Command, args []string) error { app := counter.NewCounterApplication(flagSerial) logger := log.NewTMLogger(log.NewSyncWriter(os.Stdout)) // Start the listener srv, err := server.NewServer(flagAddrC, flagAbci, app) if err != nil { return err } srv.SetLogger(logger.With("module", "abci-server")) if err := srv.Start(); err != nil { return err } // Wait forever cmn.TrapSignal(func() { // Cleanup srv.Stop() }) return nil } ``` The counter app doesn't use a Merkle tree, it just counts how many times we've sent a transaction, asked for a hash, or committed the state. The result of `commit` is just the number of transactions sent. This application has two modes: `serial=off` and `serial=on`. When `serial=on`, transactions must be a big-endian encoded incrementing integer, starting at 0. If `serial=off`, there are no restrictions on transactions. We can toggle the value of `serial` using the `set_option` ABCI message. When `serial=on`, some transactions are invalid. In a live blockchain, transactions collect in memory before they are committed into blocks. To avoid wasting resources on invalid transactions, ABCI provides the `check_tx` message, which application developers can use to accept or reject transactions, before they are stored in memory or gossipped to other peers. In this instance of the counter app, `check_tx` only allows transactions whose integer is greater than the last committed one. Let's kill the console and the kvstore application, and start the counter app: ``` abci-cli counter ``` In another window, start the `abci-cli console`: ``` > set_option serial on -> code: OK -> log: OK (SetOption doesn't return anything.) > check_tx 0x00 -> code: OK > check_tx 0xff -> code: OK > deliver_tx 0x00 -> code: OK > check_tx 0x00 -> code: BadNonce -> log: Invalid nonce. Expected >= 1, got 0 > deliver_tx 0x01 -> code: OK > deliver_tx 0x04 -> code: BadNonce -> log: Invalid nonce. Expected 2, got 4 > info -> code: OK -> data: {"hashes":0,"txs":2} -> data.hex: 0x7B22686173686573223A302C22747873223A327D ``` This is a very simple application, but between `counter` and `kvstore`, its easy to see how you can build out arbitrary application states on top of the ABCI. [Hyperledger's Burrow](https://github.com/hyperledger/burrow) also runs atop ABCI, bringing with it Ethereum-like accounts, the Ethereum virtual-machine, Monax's permissioning scheme, and native contracts extensions. But the ultimate flexibility comes from being able to write the application easily in any language. We have implemented the counter in a number of languages [see the example directory](https://github.com/tendermint/tendermint/tree/develop/abci/example). To run the Node JS version, `cd` to `example/js` and run ``` node app.js ``` (you'll have to kill the other counter application process). In another window, run the console and those previous ABCI commands. You should get the same results as for the Go version. ## Bounties Want to write the counter app in your favorite language?! We'd be happy to add you to our [ecosystem](https://tendermint.com/ecosystem)! We're also offering [bounties](https://hackerone.com/tendermint/) for implementations in new languages! The `abci-cli` is designed strictly for testing and debugging. In a real deployment, the role of sending messages is taken by Tendermint, which connects to the app using three separate connections, each with its own pattern of messages. For more information, see the [application developers guide](./app-development.md). For examples of running an ABCI app with Tendermint, see the [getting started guide](./getting-started.md). Next is the ABCI specification.