The socketio package is a simple abstraction layer for different web browser- supported transport mechanisms. It is meant to be fully compatible with the Socket.IO client JavaScript-library by LearnBoost Labs. A couple of patches to the client library are required due to the nature of canonicalization happening deep within the standard http-package. These patches will hopefully get merged into the official repository at some point. Meanwhile, use this fork of the client. Using 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:

• HTML5 WebSockets
• HTML5 WebSockets through Adobe® Flash® Sockets
• JSONP Long Polling
• XHR Long Polling
• XHR Multipart Streaming

The socketio package works hand-in-hand with the standard http package (by plugging itself into a configurable 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.Mux
• 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 codec, SIOCodec, is fully compatible with the LearnBoost's Socket.IO client.

package main

import (
	"http"
	"log"
	"socketio"
)

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) {
		sio.BroadcastExcept(c,
			struct{ announcement string }{"disconnected: " + c.String()})
	})

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

	sio.Mux("/socket.io/", nil)
	http.Handle("/", http.FileServer("www/", "/"))

	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Exit("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
$ cd example
$ make
$ ./example

(The MIT License)

Copyright (c) 2010 Jukka-Pekka Kekkonen <karatepekka@gmail.com>

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.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.