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// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// GNU Lesser General Public License for more details.
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <>.
package rpc
import (
mapset ""
const MetadataApi = "rpc"
// CodecOption specifies which type of messages a codec supports.
// Deprecated: this option is no longer honored by Server.
type CodecOption int
const (
// OptionMethodInvocation is an indication that the codec supports RPC method calls
OptionMethodInvocation CodecOption = 1 << iota
// OptionSubscriptions is an indication that the codec suports RPC notifications
OptionSubscriptions = 1 << iota // support pub sub
// Server is an RPC server.
type Server struct {
services serviceRegistry
idgen func() ID
run int32
codecs mapset.Set
// NewServer creates a new server instance with no registered handlers.
func NewServer() *Server {
server := &Server{idgen: randomIDGenerator(), codecs: mapset.NewSet(), run: 1}
// Register the default service providing meta information about the RPC service such
// as the services and methods it offers.
rpcService := &RPCService{server}
server.RegisterName(MetadataApi, rpcService)
return server
// RegisterName creates a service for the given receiver type under the given name. When no
// methods on the given receiver match the criteria to be either a RPC method or a
// subscription an error is returned. Otherwise a new service is created and added to the
// service collection this server provides to clients.
func (s *Server) RegisterName(name string, receiver interface{}) error {
return, receiver)
// ServeCodec reads incoming requests from codec, calls the appropriate callback and writes
// the response back using the given codec. It will block until the codec is closed or the
// server is stopped. In either case the codec is closed.
// Note that codec options are no longer supported.
func (s *Server) ServeCodec(codec ServerCodec, options CodecOption) {
defer codec.Close()
// Don't serve if server is stopped.
if atomic.LoadInt32(& == 0 {
// Add the codec to the set so it can be closed by Stop.
defer s.codecs.Remove(codec)
c := initClient(codec, s.idgen, &
// serveSingleRequest reads and processes a single RPC request from the given codec. This
// is used to serve HTTP connections. Subscriptions and reverse calls are not allowed in
// this mode.
func (s *Server) serveSingleRequest(ctx context.Context, codec ServerCodec) {
// Don't serve if server is stopped.
if atomic.LoadInt32(& == 0 {
h := newHandler(ctx, codec, s.idgen, &
h.allowSubscribe = false
defer h.close(io.EOF, nil)
reqs, batch, err := codec.Read()
if err != nil {
if err != io.EOF {
codec.Write(ctx, errorMessage(&invalidMessageError{"parse error"}))
if batch {
} else {
// Stop stops reading new requests, waits for stopPendingRequestTimeout to allow pending
// requests to finish, then closes all codecs which will cancel pending requests and
// subscriptions.
func (s *Server) Stop() {
if atomic.CompareAndSwapInt32(&, 1, 0) {
log.Debug("RPC server shutting down")
s.codecs.Each(func(c interface{}) bool {
return true
// RPCService gives meta information about the server.
// e.g. gives information about the loaded modules.
type RPCService struct {
server *Server
// Modules returns the list of RPC services with their version number
func (s *RPCService) Modules() map[string]string {
modules := make(map[string]string)
for name := range {
modules[name] = "1.0"
return modules
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