go-rpc

HTTP RPC server supporting calls via uri params, jsonrpc, and jsonrpc over websockets

Client Requests

Suppose we want to expose the rpc function HelloWorld(name string, num int).

GET (URI)

As a GET request, it would have URI encoded parameters, and look like:

curl 'http://localhost:8008/hello_world?name="my_world"&num=5'

Note the ' around the url, which is just so bash doesn't ignore the quotes in "my_world". This should also work:

curl http://localhost:8008/hello_world?name=\"my_world\"&num=5

A GET request to / returns a list of available endpoints. For those which take arguments, the arguments will be listed in order, with _ where the actual value should be.

POST (JSONRPC)

As a POST request, we use JSONRPC. For instance, the same request would have this as the body:

{
	"jsonrpc":"2.0",
	"id":"anything",
	"method":"hello_world",
	"params":["my_world", 5]
}

Note the params does not currently support key-value pairs (https://github.com/tendermint/go-rpc/issues/1), so order matters (you can get the order from making a GET request to /)

With the above saved in file data.json, we can make the request with

curl --data @data.json http://localhost:8008

WebSocket (JSONRPC)

All requests are exposed over websocket in the same form as the POST JSONRPC. Websocket connections are available at their own endpoint, typically /websocket, though this is configurable when starting the server.

Server Definition

Define some types and routes:

// Define a type for results and register concrete versions with go-wire
type Result interface{}

type ResultStatus struct {
	Value string
}

var _ = wire.RegisterInterface(
	struct{ Result }{},
	wire.ConcreteType{&ResultStatus{}, 0x1},
)

// Define some routes
var Routes = map[string]*rpcserver.RPCFunc{
	"status": rpcserver.NewRPCFunc(StatusResult, "arg"),
}

// an rpc function
func StatusResult(v string) (Result, error) {
	return &ResultStatus{v}, nil
}

Now start the server:

mux := http.NewServeMux()
rpcserver.RegisterRPCFuncs(mux, Routes)
wm := rpcserver.NewWebsocketManager(Routes, nil)
mux.HandleFunc("/websocket", wm.WebsocketHandler)
go func() {
	_, err := rpcserver.StartHTTPServer("0.0.0.0:8008", mux)
	if err != nil {
		panic(err)
	}
}()

Note that unix sockets are supported as well (eg. /path/to/socket instead of 0.0.0.0:8008)

Now see all available endpoints by sending a GET request to 0.0.0.0:8008. Each route is available as a GET request, as a JSONRPCv2 POST request, and via JSONRPCv2 over websockets

Examples

• Tendermint
• Network Monitor