Websockets

This example will show how to work with websockets in Go. We will build a simple server which echoes back everything we send to it. For this we have to go get the popular gorilla/websocket library like so:

$ go get github.com/gorilla/websocket

From now on, every application we write will be able to make use of this library.

  1. // websockets.go
  2. package main
  4. import (
  5.     "fmt"
  6.     "net/http"
  8.     "github.com/gorilla/websocket"
  9. )
  11. var upgrader = websocket.Upgrader{
  12.     ReadBufferSize:  1024,
  13.     WriteBufferSize: 1024,
  14. }
  16. func main() {
  17.     http.HandleFunc("/echo", func(w http.ResponseWriter, r *http.Request) {
  18.         conn, _ := upgrader.Upgrade(w, r, nil) // error ignored for sake of simplicity
  20.         for {
  21.             // Read message from browser
  22.             msgType, msg, err := conn.ReadMessage()
  23.             if err != nil {
  24.                 return
  25.             }
  27.             // Print the message to the console
  28.             fmt.Printf("%s sent: %s\n", conn.RemoteAddr(), string(msg))
  30.             // Write message back to browser
  31.             if err = conn.WriteMessage(msgType, msg); err != nil {
  32.                 return
  33.             }
  34.         }
  35.     })
  37.     http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
  38.         http.ServeFile(w, r, "websockets.html")
  39.     })
  41.     http.ListenAndServe(":8080", nil)
  42. }
  1. <!-- websockets.html -->
  2. <input id="input" type="text" />
  3. <button onclick="send()">Send</button>
  4. <pre id="output"></pre>
  5. <script>
  6.     var input = document.getElementById("input");
  7.     var output = document.getElementById("output");
  8.     var socket = new WebSocket("ws://localhost:8080/echo");
  10.     socket.onopen = function () {
  11.         output.innerHTML += "Status: Connected\n";
  12.     };
  14.     socket.onmessage = function (e) {
  15.         output.innerHTML += "Server: " + e.data + "\n";
  16.     };
  18.     function send() {
  19.         socket.send(input.value);
  20.         input.value = "";
  21.     }
  22. </script>
  1. $ go run websockets.go
  2. [127.0.0.1]:53403 sent: Hello Go Web Examples, you're doing great!