What is SockJS?

SockJS is a JavaScript library (for browsers) that provides a WebSocket-like object. SockJS gives you a coherent, cross-browser, Javascript API which creates a low latency, full duplex, cross-domain communication channel between the browser and the web server, with WebSockets or without. This necessitates the use of a server, which this is one version of, for GO.

SockJS-Go server library

SockJS-Go is a SockJS server library written in Go.

For latest v3 version of sockjs-go use:

github.com/igm/sockjs-go/v3/sockjs

For v2 version of sockjs-go use:

gopkg.in/igm/sockjs-go.v2/sockjs

Using version v1 is not recommended (DEPRECATED)

gopkg.in/igm/sockjs-go.v1/sockjs

Note: using github.com/igm/sockjs-go/sockjs is not recommended. It exists for backwards compatibility reasons and is not maintained.

Versioning

SockJS-Go project adopted gopkg.in approach for versioning. SockJS-Go library details can be found here

With the introduction of go modules a new version v3 is developed and maintained in the master and has new import part github.com/igm/sockjs-go/v3/sockjs.

Example

A simple echo sockjs server:

package main

import (
	"log"
	"net/http"

	"github.com/igm/sockjs-go/v3/sockjs"
)

func main() {
	handler := sockjs.NewHandler("/echo", sockjs.DefaultOptions, echoHandler)
	log.Fatal(http.ListenAndServe(":8081", handler))
}

func echoHandler(session sockjs.Session) {
	for {
		if msg, err := session.Recv(); err == nil {
			session.Send(msg)
			continue
		}
		break
	}
}

SockJS Protocol Tests Status

SockJS defines a set of protocol tests to quarantee a server compatibility with sockjs client library and various browsers. SockJS-Go server library aims to provide full compatibility, however there are couple of tests that don't and probably will never pass due to reasons explained in table below:

Failing Test	Explanation
XhrPolling.test_transport	does not pass due to a feature in net/http that does not send content-type header in case of StatusNoContent response code (even if explicitly set in the code), details
WebSocket.	Sockjs Go version supports RFC 6455, draft protocols hixie-76, hybi-10 are not supported
JSONEncoding	As menioned in browser quirks section: "it's advisable to use only valid characters. Using invalid characters is a bit slower, and may not work with SockJS servers that have a proper Unicode support." Go lang has a proper Unicode support
RawWebsocket.	The sockjs protocol tests use old WebSocket client library (hybi-10) that does not support RFC 6455 properly

WebSocket

As mentioned above sockjs-go library is compatible with RFC 6455. That means the browsers not supporting RFC 6455 are not supported properly. There are no plans to support draft versions of WebSocket protocol. The WebSocket support is based on Gorilla web toolkit implementation of WebSocket.

For detailed information about browser versions supporting RFC 6455 see this wiki page.