websocket

websocket is a minimal and idiomatic WebSocket library for Go.

Install

go get nhooyr.io/websocket

Features

• Minimal and idiomatic API
• Tiny codebase at 1700 lines
• First class context.Context support
• Thorough tests, fully passes the autobahn-testsuite
• Zero dependencies
• JSON and ProtoBuf helpers in the wsjson and wspb subpackages
• Highly optimized by default
• Concurrent writes out of the box

Roadmap

• WebSockets over HTTP/2 #4
• WASM Compilation #121

Examples

For a production quality example that shows off the full API, see the echo example on the godoc. On github, the example is at example_echo_test.go.

Use the errors.As function new in Go 1.13 to check for websocket.CloseError. See the CloseError godoc example.

Server

http.HandlerFunc(func (w http.ResponseWriter, r *http.Request) {
	c, err := websocket.Accept(w, r, nil)
	if err != nil {
		// ...
	}
	defer c.Close(websocket.StatusInternalError, "the sky is falling")

	ctx, cancel := context.WithTimeout(r.Context(), time.Second*10)
	defer cancel()

	var v interface{}
	err = wsjson.Read(ctx, c, &v)
	if err != nil {
		// ...
	}

	log.Printf("received: %v", v)

	c.Close(websocket.StatusNormalClosure, "")
})

Client

The client side of this library requires at least Go 1.12 as it uses a new feature in net/http to perform WebSocket handshakes.

ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
defer cancel()

c, _, err := websocket.Dial(ctx, "ws://localhost:8080", nil)
if err != nil {
	// ...
}
defer c.Close(websocket.StatusInternalError, "the sky is falling")

err = wsjson.Write(ctx, c, "hi")
if err != nil {
	// ...
}

c.Close(websocket.StatusNormalClosure, "")

Design justifications

• A minimal API is easier to maintain due to less docs, tests and bugs
• A minimal API is also easier to use and learn
• Context based cancellation is more ergonomic and robust than setting deadlines
• net.Conn is never exposed as WebSocket over HTTP/2 will not have a net.Conn.
• Using net/http's Client for dialing means we do not have to reinvent dialing hooks and configurations like other WebSocket libraries
• We do not support the deflate compression extension because Go's compress/flate library is very memory intensive and browsers do not handle WebSocket compression intelligently. See #5

Comparison

Before the comparison, I want to point out that both gorilla/websocket and gobwas/ws were extremely useful in implementing the WebSocket protocol correctly so big thanks to the authors of both. In particular, I made sure to go through the issue tracker of gorilla/websocket to ensure I implemented details correctly and understood how people were using WebSockets in production.

gorilla/websocket

https://github.com/gorilla/websocket

This package is the community standard but it is 6 years old and over time has accumulated cruft. There are too many ways to do the same thing. Just compare the godoc of nhooyr/websocket side by side with gorilla/websocket.

The API for nhooyr/websocket has been designed such that there is only one way to do things which makes it easy to use correctly. Not only is the API simpler, the implementation is only 1700 lines whereas gorilla/websocket is at 3500 lines. That's more code to maintain, more code to test, more code to document and more surface area for bugs.

Moreover, nhooyr/websocket has support for newer Go idioms such as context.Context and also uses net/http's Client and ResponseWriter directly for WebSocket handshakes. gorilla/websocket writes its handshakes to the underlying net.Conn which means it has to reinvent hooks for TLS and proxies and prevents support of HTTP/2.

Some more advantages of nhooyr/websocket are that it supports concurrent writes and makes it very easy to close the connection with a status code and reason.

The ping API is also nicer. gorilla/websocket requires registering a pong handler on the Conn which results in awkward control flow. With nhooyr/websocket you use the Ping method on the Conn that sends a ping and also waits for the pong, though you must be reading from the connection for the pong to be read.

In terms of performance, the differences mostly depend on your application code. nhooyr/websocket reuses message buffers out of the box if you use the wsjson and wspb subpackages. As mentioned above, nhooyr/websocket also supports concurrent writers.

The only performance con to nhooyr/websocket is that uses one extra goroutine to support cancellation with context.Context. This costs 2 KB of memory which is cheap compared to the benefits.

x/net/websocket

https://godoc.org/golang.org/x/net/websocket

Unmaintained and the API does not reflect WebSocket semantics. Should never be used.

See https://github.com/golang/go/issues/18152

gobwas/ws

https://github.com/gobwas/ws

This library has an extremely flexible API but that comes at the cost of usability and clarity.

This library is fantastic in terms of performance. The author put in significant effort to ensure its speed and I have applied as many of its optimizations as I could into nhooyr/websocket. Definitely check out his fantastic blog post about performant WebSocket servers.

If you want a library that gives you absolute control over everything, this is the library, but for most users, the API provided by nhooyr/websocket will fit better as it is nearly just as performant but much easier to use correctly and idiomatic.

Contributing

See .github/CONTRIBUTING.md.

Users

If your company or project is using this library, feel free to open an issue or PR to amend this list.

• Coder
• Tatsu Works - Ingresses 20 TB in websocket data every month on their Discord bot.