Websocket not working
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anthon...@gmail.com
Feb 23, 2016, 3:27:16 PM2/23/16
to golang-nuts
Hi. Golang newbie here so my apologies if this is obvious :(
I've copied and pasted a websockets example but it is not working.
When I open the web page I get: Firefox can't establish a connection to the server at ws://localhost:8080/echo.
The code I copied is listed below.
Any help would be much appreciated.
Go code
======
package main
import (
"golang.org/x/net/websocket"
"net/http"
"fmt"
)
func echoHandler(ws *websocket.Conn) {
for {
receivedtext := make([]byte, 100)
n,err := ws.Read(receivedtext)
if err != nil {
fmt.Printf("Received: %d bytes\n",n)
}
s := string(receivedtext[:n])
fmt.Printf("Received: %d bytes: %s\n",n,s)
}
}
func main() {
http.Handle("/echo", websocket.Handler(echoHandler))
http.Handle("/", http.FileServer(http.Dir(".")))
err := http.ListenAndServe(":8080", nil)
if err != nil {
panic("Error: " + err.Error())
}
}
Web page
=======
<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>
I've copied and pasted a websockets example but it is not working.
When I open the web page I get: Firefox can't establish a connection to the server at ws://localhost:8080/echo.
The code I copied is listed below.
Any help would be much appreciated.
Go code
======
package main
import (
"golang.org/x/net/websocket"
"net/http"
"fmt"
)
func echoHandler(ws *websocket.Conn) {
for {
receivedtext := make([]byte, 100)
n,err := ws.Read(receivedtext)
if err != nil {
fmt.Printf("Received: %d bytes\n",n)
}
s := string(receivedtext[:n])
fmt.Printf("Received: %d bytes: %s\n",n,s)
}
}
func main() {
http.Handle("/echo", websocket.Handler(echoHandler))
http.Handle("/", http.FileServer(http.Dir(".")))
err := http.ListenAndServe(":8080", nil)
if err != nil {
panic("Error: " + err.Error())
}
}
Web page
=======
<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>
Reed O'Brien
Feb 23, 2016, 3:56:35 PM2/23/16
to golang-nuts, anthon...@gmail.com
Are you accessing the html page via a file:///home/you/index.html?
If so that could be your issue. Try accessing it through another web server[1] or serving it from another handler in your app.
[1] There's dozens out there, and it is as simple as https://github.com/golang/go/wiki/HttpStaticFiles, but I use the following for ad hoc local needs: https://github.com/reedobrien/dserve
C Banning
Feb 24, 2016, 9:03:42 AM2/24/16
to golang-nuts, anthon...@gmail.com
You've got a couple of things going on -
- your echoHandler() needs a ws.Write(receivedtext[:n]) to "echo" the message back to the browser app.
- you must launch the browser app from the directory listing: http://localhost:8080 - if you launch the browser app directly from the file system the browser will block access to localhost:8080 because it looks like cross-origin resource sharing (CORS) and the web socket.Handler doesn't support that. (That's why you get the 403 error when Firefox tries to establish the connection.)
anthon...@gmail.com
Feb 26, 2016, 1:50:24 AM2/26/16
to golang-nuts, anthon...@gmail.com
Doh, I was launching the browser app from a file.
It's working properly now.
Thanks Reed O'Brien and C Banning for your help :)
Anthony
It's working properly now.
Thanks Reed O'Brien and C Banning for your help :)
Anthony
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