A Socket.IO backend implementation written in Go



The socketio package is a simple abstraction layer for different web browser- supported transport mechanisms. It is fully compatible with the Socket.IO client (version 0.6) JavaScript-library by LearnBoost Labs. By writing custom codecs the socketio could be perhaps used with other clients, too.

It provides an easy way for developers to rapidly prototype with the most popular browser transport mechanism today:

Compatibility with Socket.IO 0.7->

Go-socket.io is currently compatible with Socket.IO 0.6 clients only.


The Paper Experiment

Crash course

The socketio package works hand-in-hand with the standard http package (by plugging itself into http.ServeMux) and hence it doesn't need a full network port for itself. It has an callback-style event handling API. The callbacks are:

  • SocketIO.OnConnect
  • SocketIO.OnDisconnect
  • SocketIO.OnMessage

Other utility-methods include:

  • SocketIO.ServeMux
  • SocketIO.Broadcast
  • SocketIO.BroadcastExcept
  • SocketIO.GetConn

Each new connection will be automatically assigned an session id and using those the clients can reconnect without losing messages: the server persists clients' pending messages (until some configurable point) if they can't be immediately delivered. All writes are by design asynchronous and can be made through Conn.Send. The server also abstracts handshaking and various keep-alive mechanisms.

Finally, the actual format on the wire is described by a separate Codec. The default bundled codecs, SIOCodec and SIOStreamingCodec are fully compatible with the LearnBoost's Socket.IO client (master and development branches).

Example: A simple chat server

package main

import (

func main() {
	sio := socketio.NewSocketIO(nil)

	sio.OnConnect(func(c *socketio.Conn) {
		sio.Broadcast(struct{ announcement string }{"connected: " + c.String()})

	sio.OnDisconnect(func(c *socketio.Conn) {
			struct{ announcement string }{"disconnected: " + c.String()})

	sio.OnMessage(func(c *socketio.Conn, msg socketio.Message) {
			struct{ message []string }{[]string{c.String(), msg.Data()}})

	mux := sio.ServeMux()
	mux.Handle("/", http.FileServer("www/", "/"))

	if err := http.ListenAndServe(":8080", mux); err != nil {
		log.Fatal("ListenAndServe:", err)


You can get the code and run the bundled example by following these steps:

$ git clone git://github.com/madari/go-socket.io.git
$ cd go-socket.io
$ git submodule update --init --recursive
$ make install
$ cd example
$ make
$ ./example


(The MIT License)

Copyright (c) 2011 Jukka-Pekka Kekkonen <[email protected]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.


  • Tip make go1 compatible

    Tip make go1 compatible

    Hi Jukka,

    I did the minimal changes to make your nice go-socket.io package compatible with Go 1.0.x. It compiles and all unit tests run.

    Please review the error handling around syscall.EAGAIN. I guess this needs to be reworked a little.

    The example works for me, after changing the importing socketio like this socketio "github.com/nightlyone/go-socket.io"

    I guess you wanna change this to "github.com/madari/go-socket.io" after the pull.

    Thanks for your consideration.

    Best Regards

    Ingo Oeser, aka nightlyone

    opened by nightlyone 4
  • Out of Date Protocol

    Out of Date Protocol

    Socket.IO is on 0.8.4 now; the protocol has been upgraded quite a bit. Are there any plans to upgrade this library to match? Is there anything you could use help on in bringing the project up to date? I'd love to see if I could get this working on App Engine as an alternative to the Channel API. Google's App Engine team is really interested to see what happens if it can work, too.

    opened by paddycarver 4
  • Patches justinfx

    Patches justinfx

    Done a number of things to the library:

    Memory Fixes: *There were some areas in the codecs where buffers were not being reset and memory kept growing. Changes some areas to use []byte instead of string. I still think there might be some memory leaks, but it requires more testing. I think memory will continue to grow as you pound the server with many connections sending many message. But its less a problem now that it was before


    • Heartbeats have been split off into a separate goroutine so it doesn't become impacted by heavy message tracffic and drop users.


    • Added an authorization hook into the handler so that the user can specify a function that returns bool on whether the connection is authorized, based on the request.
    opened by justinfx 3
  • connection.go: reader() - cannot send messages over 4096 bytes

    connection.go: reader() - cannot send messages over 4096 bytes

    It seems that even though you can set c.sio.config.ReadBufferSize to any size, the underlying transport buffers are still using the default 4096 buffer value? So as it stands, if you increase ReadBufferSize beyond 4096 and send a large message, you get a bufio: Buffer Full, which is unhandled and drops the connection. I have been trying to work out a temporary solution where it checks for this error, and continues to loop and build the total amount until EOF. But mainly its been a hack.

    Is this something that is going to be solved in the streaming codec with v0.7? Or can you see any clear solutions as it stands? I was able to get my hack to work in the sense of allowing an unlimited size message, but obviously that is not desirable, and the value of ReadBufferSize should really set a true limit. Maybe there needs to be a MaxMessageSize or something, so the ReadBufferSize can keep being reused to build up the total message UP TO MaxMessageSize. If it exceeds that, it would send back some kind of socketio failure, or, i guess drop the connection still.

    opened by justinfx 2
  • connection.go:327: undefined: closed

    connection.go:327: undefined: closed

    The latest Go update breaks make...

    [james@love go-socket.io]$ make clean rm -rf _.o *.a *.[568vq] [568vq].out *.so _obj _test _testmain.go *.exe cgo .cgo[12]. test.out build.out [james@love go-socket.io]$ make 6g -o go.6 util.go servemux.go message.go config.go session.go socketio.go connection.go codec.go codec_sio.go codec_siostreaming.go transport.go transport_xhrpolling.go transport_xhrmultipart.go transport_htmlfile.go transport_websocket.go transport_flashsocket.go transport_jsonppolling.go client.go doc.go connection.go:327: undefined: closed connection.go:375: undefined: closed make: *** [go.6] Error 1

    opened by jamesthornton 2
  • fixes for handling

    fixes for handling "Origin" Header

    • Header["Origin"] was returning a slice, which was directly formatted into the response Header and would fail to match the original origin. Using Header.Get("Origin") now
    opened by justinfx 1
  • Message and Codec fixes

    Message and Codec fixes

    Extracted from larger pull req The changes to the codec_*test.go files was because it passed the gotest under the release. Not sure if you were testing under a certain weekly build or not.

    opened by justinfx 1
  • Use CodeLingo to Address Further Issues

    Use CodeLingo to Address Further Issues

    Hi @madari!

    Thanks for merging the fixes from our earlier pull request. They were generated by CodeLingo which we've used to find a further 187 issues in the repo. This PR adds a set of CodeLingo Tenets which catch any new cases of the found issues in PRs to your repo.

    CodeLingo will also send follow-up PRs to fix the existing repos in the codebase. Install CodeLingo GitHub app after merging this PR. It will always be free for open source.

    We're most interested to see if we can help with project specific bugs. Tell us about more interesting issues and we'll see if our tech can help - free of charge.

    Thanks, Leila and the CodeLingo Team

    opened by CodeLingoTeam 0
  • go 1 support

    go 1 support

    on gnanderson's branch i have tried to do some a basic update but it would be great if you could update the repository name to the package name socketio https://github.com/gnanderson/go-socket.io/pull/1

    opened by dspiteself 0
  • fix for interface conversion error

    fix for interface conversion error

    trying to connect (jsonp-polling, xhr-long polliing) using https protocol throws the following error.

    panic: interface conversion: net.Conn is *tls.Conn, not *net.TCPConn [recovered] panic: runtime error: invalid memory address or nil pointer dereference

    opened by lmumar 0
  • connection.go:265 -  unable to queue heartbeat. fail now. TODO: FIXME

    connection.go:265 - unable to queue heartbeat. fail now. TODO: FIXME

    Let me just start by saying thank you so much for this library. I am learning Go right now by porting a Message Server over from python (Tornado, TornadIO, ZMQ) to Go and I'm really excited by these bindings so far!

    I'm hitting one of your Fix Me's in connection.go:265 c.sio.Log("sio/keepalive: unable to queue heartbeat. fail now. TODO: FIXME", c)

    What I am doing is rapid fire throughput tests with a command line client. When I use only a single client, I dont hit this wall. When I run 2 concurrent connections, the messaging hangs on this for a moment and ultimately then finishes, returning these errors after all the queued messages have been delivered.

    My question is mainly about what is really happening here. Does it have anything to do with the heartbeats being queued on the same channel as the messages, and they are saturating the buffer to where heartbeats cant get through? Or is it a matter of raising the queue length value? Is it a situation where ideally the heartbeat needs to be suspended while there is actual activity?

    Thanks! -- justin

    Accepted Defect 
    opened by justinfx 7
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