Gorilla Websockets, golang simple websockets example
I previously posted a quick example of using the standard library websockets API in golang. Unfortunately there are a number of issues that make difficult to use in practice. Notably, it lacks support for PING/PONG packets which are often used to for KeepAlive functionality in websockets. This is particularly important, as browsers tend to be aggressive in killing off these connections.
So, here’s a quick complete example of Gorilla Websockets in golang, with similar functionality to that I posted previously. It simply echos everything it receives back to the client. First the golang code:
package main
import (
"github.com/gorilla/websocket"
"net/http"
"fmt"
)
var upgrader = websocket.Upgrader{
ReadBufferSize: 1024,
WriteBufferSize: 1024,
}
func print_binary(s []byte) {
fmt.Printf("Received b:");
for n := 0;n < len(s);n++ {
fmt.Printf("%d,",s[n]);
}
fmt.Printf("\n");
}
func echoHandler(w http.ResponseWriter, r *http.Request) {
conn, err := upgrader.Upgrade(w, r, nil)
if err != nil {
//log.Println(err)
return
}
for {
messageType, p, err := conn.ReadMessage()
if err != nil {
return
}
print_binary(p)
err = conn.WriteMessage(messageType, p);
if err != nil {
return
}
}
}
func main() {
http.HandleFunc("/echo", echoHandler)
http.Handle("/", http.FileServer(http.Dir(".")))
err := http.ListenAndServe(":8080", nil)
if err != nil {
panic("Error: " + err.Error())
}
}
And then the html used to interface with the websocket. Save it in the same directory as the golang program, and access it at: http://localhost:8080/filename.html
<html>
<head>
<meta charset="UTF-8" />
<script>
var serversocket = new WebSocket("ws://localhost:8080/echo");
serversocket.onopen = function() {
serversocket.send("Connection init");
}
// Write message on receive
serversocket.onmessage = function(e) {
document.getElementById('comms').innerHTML += "Received: " + e.data + "<br>";
};
function senddata() {
var data = document.getElementById('sendtext').value;
serversocket.send(data);
document.getElementById('comms').innerHTML += "Sent: " + data + "<br>";
}
</script>
</head>
<body>
<input id="sendtext" type="text" />
<input type="button" id="sendBtn" value="send" onclick="senddata()"></input>
<div id='comms'></div>
</body>
</html>
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