Golang Server close the connection of the client : websocket - websocket

Question

i have a problem with my golang server in which i'm using websockets.
The server opens the connection and the client could connect to it, but the problem is that when the server starts sending the data to the client, the client connection is closed after a small period of time. i suggest that the problem is with the server and not with the client because i tried to connect to the server with another web client, and it's the same issue. I didn't understand the cause ! Can someone help me?
server.go:
func Echo(ws *websocket.Conn) {
fmt.Println("Echoing")
for {
msg := MessageReceived{Name: "OrderCommand", Nbmsg: 3}
if err := websocket.JSON.Send(ws, msg); err != nil {
fmt.Println("Can't send")
break
}
//os.Exit(0)
}
}
func checkError(err error) {
if err != nil {
Log("Fatal error ", err.Error())
os.Exit(1)
}
}
func main() {
http.HandleFunc("/save", saveHandler)
http.Handle("/", websocket.Handler(Echo))
err:= http.ListenAndServe(":8081", nil)
checkError(err)
}
and client.go:
import (
"code.google.com/p/go.net/websocket"
"fmt"
"log"
)
func main() {
origin := "http://localhost/"
url := "ws://localhost:8081/echo"
ws, err := websocket.Dial(url, "", origin)
if err != nil {
log.Fatal(err)
}
var msg = make([]byte, 512)
var n int
if n, err = ws.Read(msg); err != nil {
log.Fatal(err)
}
fmt.Printf("Received: %s.\n", msg[:n])
}

Answer 1

Your problem, as others have pointed out, is that you must receive a message as well.
Currently, when someone connects, your program will step into the for-loop and start bombarding the client with messages. Probably not the intended behaviour of an echo server.
First you want to Receive a message, then Send a reply:
func Echo(ws *websocket.Conn) {
fmt.Println("Echoing")
msg := new(MessageReceived)
for {
// The server blocks here until a message from the client is received
websocket.JSON.Receive(ws, &msg)
fmt.Printf("Received message: %+v\n", msg)
// Reencode the same message and send it back
if err := websocket.JSON.Send(ws, msg); err != nil {
fmt.Println("Can't send echo")
break
}
}
}
A full working version can be found at Playground: http://play.golang.org/p/nQ3fJ5Nb0I
Since it uses websockets, you must compile it on your local computer.

Answer 2

Why using ws.Read when you can use websocket.JSON.Receive to deserialize the message?
Here are the server: http://play.golang.org/p/NZ6VJ4daGm
and the client: http://play.golang.org/p/rkJVKGhrGk (that I have changed to receive 10 messages before exiting).
The string "Can't send" will be printed by the server once the client closes the websocket connection.