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websocket: Client not using websocket protocol: 'Upgrade' token not found in 'Connection' header

王林forward: 2024-02-09 14:24:101449browse

websocket：客户端未使用 websocket 协议：“连接”标头中未找到“升级”令牌

When making a WebSocket connection, sometimes the error "Client is not using the WebSocket protocol: 'Upgrade' token not found in 'Connection' header" error will appear. This error is usually caused by the client not using the WebSocket protocol correctly. WebSocket is a protocol that enables two-way communication between a client and a server, using a special handshake process to establish a connection. During the handshake, the client needs to properly send the "Upgrade" header to indicate the use of the WebSocket protocol. If the client does not send this header correctly, the server will return the above error. PHP editor Baicao will introduce in detail how to solve this problem in this article so that your WebSocket connection can proceed smoothly.

Question content

I'm trying to establish a websocket connection to a server written in go and javascript frontend. I have the following files in a directory:

main.go index.html

**This is my go code in main.go: **

package main


import (
    "fmt"
    "log"
    "net/http"

    "github.com/gorilla/websocket"
)

var upgrader = websocket.upgrader{
    readbuffersize:  1024,
    writebuffersize: 1024,
}

func homepage(w http.responsewriter, r *http.request) {
    http.servefile(w, r, "./index.html")
    conn, err := upgrader.upgrade(w, r, nil)
    if err != nil {
        log.println("error in handler:", err)
        return
    }
    log.println("client connected.")

    for {
        messagetype, p, err := conn.readmessage()
        if err != nil {
            log.println("fehler in readmessage: ", err)
            return
        }

        log.println(string(p))

        //echo message to client
        if err := conn.writemessage(messagetype, p); err != nil {
            log.println(err)
            return
        }
    }
}

func setuproutes() {
    http.handlefunc("/ws", homepage)
}

func main() {
    fmt.println("server gestartet")
    setuproutes()
    log.fatal(http.listenandserve(":9100", nil))

}

This is the html and javascript in index.html:

<!doctype html>
<html lang="de">
<head>
    <meta charset="utf-8">
    <title>some unimportant html </title>
</head>
<body>
    
    <script>


        let socket = new websocket("ws://localhost:9100/ws");
        console.log("websocket started.");

        socket.onopen = () => {
            console.log("client started.");
        }

        socket.onclose = (event) => {
            console.log("socket closed: ", event);
        }

        socket.onerror = (error) => {
            console.log("socket error: ", error);
        }

        socket.onmessage = (msg) => {
            console.log(msg);
        }
    </script>
</body>
</html>

However, when I run the thing using go run main.go I get the following error:

2022/11/20 16:38:33 http: superfluous response.writeheader call from github.com/gorilla/websocket.(*upgrader).returnerror (server.go:83)
2022/11/20 16:38:33 error in handler: websocket: the client is not using the websocket protocol: 'upgrade' token not found in 'connection' header
2022/11/20 16:38:33 error in handler: write tcp [::1]:9100->[::1]:63712: wsasend: eine bestehende verbindung wurde softwaregesteuert durch den hostcomputer abgebrochen.
2022/11/20 16:39:06 error in handler: write tcp [::1]:9100->[::1]:63733: wsasend: eine bestehende verbindung wurde softwaregesteuert durch den hostcomputer abgebrochen.
exit status 0xc000013a

The German meaning is "The existing connection is terminated under the control of the host software"

I'm missing something, and my understanding isn't deep enough to figure out what the problem is. Any help is greatly appreciated!

I thought maybe my js websocket was missing an upgrade, but in chrome I can see the following request header for the request url ws://localhost:9100/ws which says "upgrade:websocket"

Accept-Encoding: gzip, deflate, br
Accept-Language: de-DE,de;q=0.9,en-US;q=0.8,en;q=0.7
Cache-Control: no-cache
Connection: Upgrade
Host: localhost:9100
Origin: http://localhost:9100
Pragma: no-cache
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
Sec-WebSocket-Key: h3DWLuXsI9/GkTo+sIjyzw==
Sec-WebSocket-Version: 13
Upgrade: websocket
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

Solution

I was able to fix it thanks to cerise limón's helpful comment. The problem is that I need one endpoint for indexing files and another for websockets. So I changed the relevant part to:

func websocketHandler(w http.ResponseWriter, r *http.Request) {
    conn, err := upgrader.Upgrade(w, r, nil) //conn is a websocket connection (aus http wird websocket protokoll)
    if err != nil {
        log.Println("Error in handler:", err)
        return
    }
    log.Println("Client connected.")

    
    for {
        messageType, p, err := conn.ReadMessage()
        if err != nil {
            log.Println("Fehler in ReadMessage: ", err)
            return
        }

        log.Println(string(p))

        //echo message to client
        if err := conn.WriteMessage(messageType, p); err != nil {
            log.Println(err)
            return
        }
    }
}

func homePage(w http.ResponseWriter, r *http.Request) {
    http.ServeFile(w, r, "./index.html")
}

func setupRoutes() {
    http.HandleFunc("/", homePage)
    http.HandleFunc("/ws", websocketHandler)

}

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