使用Websocket向客户端广播服务器端消息

Question

I am new to Golang, I am trying to a create a WebSocket server which will broadcast messages to the connected clients. The messages here will be generated from the server side(by creating a default client).

Here is my client.go

c, _, err := websocket.DefaultDialer.Dial(u.String(), nil)
if err != nil {
    log.Fatal("dial:", err)
}
defer c.Close()
done := make(chan struct{})
new_chan := make(chan string)
//defer new_chan.Stop()
go func() {
    for {
        new_chan <- "my message"
    }
}()

hub := newHub()
go hub.run()
client := &Client{hub: hub, ws: c, send: make(chan []byte, 256)}

for {
    select {
    case <-done:
        return
    case t := <-new_chan:
        err := c.WriteMessage(websocket.TextMessage, []byte(t))
        if err != nil {
            log.Println("write:", err)
            return
        }
        log.Printf(t)
        client.hub.broadcast <- bytes.TrimSpace(bytes.Replace([]byte(t), newline, space, -1))
    }
}

this function will generate the messages and try to broadcast to other clients.

server.go will add the clients to the hub

func echo(w http.ResponseWriter, r *http.Request) {
c, err := upgrader.Upgrade(w, r, nil)
if err != nil {
    log.Print("upgrade:", err)
    return
}
hub := newHub()
go hub.run()

client := &Client{hub: hub, ws: c, send: make(chan []byte, 256)}
client.hub.register <- client

go client.writePump()

writePump() here will listen to the client.send channel and broadcast messages Now the connected client's hub is different is from the hub of the client at the server. So when I try to send messages, I am not receiving anything. How can I make it belong to the same hub(context)?

Answer 1

It looks like you are starting from the Gorilla chat example. In that example, use hub.broadcast <- message to broadcast a message to all clients where hub is the *Hub created in main().

There's no need to create a client connection to send message originated from the server.

Here's a modified version of the main() that broadcasts "hello" to all clients every second:

func broadcast(hub *Hub) {
    m := []byte("hello")
    for range time.NewTicker(time.Second).C {
        hub.broadcast <- m
    }
}

func main() {
    flag.Parse()
    hub := newHub()
    go hub.run()
    go broadcast(hub)
    http.HandleFunc("/", serveHome)
    http.HandleFunc("/ws", func(w http.ResponseWriter, r *http.Request) {
        serveWs(hub, w, r)
    })
    err := http.ListenAndServe(*addr, nil)
    if err != nil {
        log.Fatal("ListenAndServe: ", err)
    }
}