如何从golang的websocket服务器向客户端主动发送消息

问题描述：

I'm a newcomer for the golang and websocket.

I'm trying to write a websocket server which can send the messages actively to client once the handshake is done.

but my server will just only send the message to the client when got the request from the client.

Does anyone know how to implement this feature or where can I find the related answer for that?

Thank you so much.

the source code is as follows:

package main

import (
    "log"
    "net/http"
)

func handler(w http.ResponseWriter, req *http.Request) {
    w.Header().Set("Content-Type", "text/plain")
    w.Write([]byte("Hi, the handshake is completed.
"))
    w.Write([]byte("Let's start to talk something.
"))
}

func main() {
    http.HandleFunc("/", handler)
    log.Printf("Start to listen on 443.")
    err := http.ListenAndServeTLS(":443", "server.crt", "server.key", nil)
    log.Fatal(err)
}

我是golang和websocket的新手。 p>

我' m尝试编写一个websocket服务器，一旦握手完成，该服务器便可以将消息主动发送给客户端。 p>

，但是我的服务器只会在收到来自服务器的请求后才将消息发送给客户端客户端。 p>

有人知道如何实现此功能，或者在哪里可以找到相关的答案？ p>

非常感谢。 p>

源代码如下： p>

 程序包主要 
 
import（
“ log” 
“ net / http” 
）
 
func处理程序（带有http.ResponseWriter，req * http.Request）{
 w.Header（）。Set（“ Content  -Type“，” text / plain“）
 w.Write（[] byte（”嗨，握手完成了。
“））
 w.Write（[] byte（”让我们开始谈谈。  
“））
} 
 
func main（）{
 http.HandleFunc（” /“，handler）
 log.Printf（”开始侦听443。“）
 err：= http。  ListenAndServeTLS（“：443”，“ server.crt”，“ server.key”，nil）
 log.Fatal（err）
} 
  code>  pre> 
  div>

答

Try package websocket.

Here's a simple example grab from the Godoc:

var upgrader = websocket.Upgrader{
    ReadBufferSize:  1024,
    WriteBufferSize: 1024,
}

func handler(w http.ResponseWriter, r *http.Request) {
    conn, err := upgrader.Upgrade(w, r, nil)
    if err != nil {
        log.Println(err)
        return
    }
    defer conn.Close()

    msg := []byte("Let's start to talk something.")
    err = conn.WriteMessage(websocket.TextMessage, msg)
    if err != nil {
        log.Println(err)
    }

    // do other stuff...
}

答

first of all, youre server is on http not websocket (for that you can upgrade it to websocket using gorilla e.g)

second, before client making a request there is no way to response him because you have no connection with him (daaa)

答

Thanks you all for you both's help to answer me. and sorry for the very late reply here.

You both's answer is really helpful and I learn a lot.

Finally, I also find the simple way to achieve the same result without using the gorilla, here comes my code:

package main

import (
    "fmt"
    "log"
    "net/http"
    "golang.org/x/net/websocket"
)

func Echo(ws *websocket.Conn) {
    var err error
    msg := `Hi, the handshake it complete!`

    for {
        if err = websocket.Message.Send(ws, msg); err != nil {
            fmt.Println("Can't send")
        } else {
            fmt.Println("Sending")
        }
    }
}

func main() {
    http.Handle("/", websocket.Handler(Echo))

    if err := http.ListenAndServeTLS("10.10.10.10:1010", "server.crt", "server.key", nil); err != nil {
        log.Fatal("ListenAndServe:", err)
    }
}

如何从golang的websocket服务器向客户端主动发送消息

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