Go language Websocket development guide: How to deal with message loss problem

Go Language Websocket Development Guide: How to Handle Message Loss Problem

1. Introduction
   In modern network applications, real-time messaging becomes more and more important The more important it is. As a two-way communication protocol, Websocket can establish a persistent connection between the client and the server and realize real-time data transmission. However, message loss may occur due to network instability or other reasons. This article will introduce how to use Go language to develop Websocket applications and deal with message loss problems.
2. Use Go language to develop Websocket applications
   Go language provides a series of powerful standard libraries for Websocket, which is very simple to use.

First, you need to import the net/http and github.com/gorilla/websocket packages.

import (
    "net/http"
    "github.com/gorilla/websocket"
)

Next, create a websocket processor:

func handleWebsocket(w http.ResponseWriter, r *http.Request) {
    // 允许跨域连接
    upgrader := websocket.Upgrader{
        CheckOrigin: func(r *http.Request) bool { return true },
    }

    // 升级HTTP连接为Websocket连接
    conn, err := upgrader.Upgrade(w, r, nil)
    if err != nil {
        log.Println("Websocket upgrade failed: ", err)
        return
    }

    // 处理消息
    for {
        messageType, message, err := conn.ReadMessage()
        if err != nil {
            log.Println("Read error: ", err)
            break
        }

        // 处理消息逻辑
        handleMessage(message)

        // 回复消息
        err = conn.WriteMessage(messageType, message)
        if err != nil {
            log.Println("Write error: ", err)
            break
        }
    }

    // 关闭连接
    conn.Close()
}

In the above code, we first upgrade the HTTP connection to a Websocket connection through the Upgrader structure. Then it loops to read, process, and reply messages until an exception occurs or the connection is closed.

Finally, create an HTTP server and register the Websocket processor to the specified path:

http.HandleFunc("/websocket", handleWebsocket)
http.ListenAndServe(":8000", nil)

3. Handling the message loss problem
   In Websocket applications, sometimes it may Messages may be lost due to network problems and other reasons. In order to solve this problem, we can use some technical means.

3.1 Message confirmation mechanism
You can add a unique identifier (such as an incremented sequence number) to the message. When the receiver receives the message, it sends a confirmation message to the sender. When the sender does not receive the confirmation message within a certain period of time, it needs to resend the message.

We can define a structure to handle the message confirmation mechanism:

type Message struct {
    ID       int
    Content  string
    AckChan  chan int
}

type MessageHandler struct {
    messages map[int]Message
}

func (handler *MessageHandler) handleMessage(message Message) {
    // 处理消息逻辑
    // ...

    // 发送确认消息
    message.AckChan <- message.ID
}

In the handleWebsocket function, we can process the message in the following way:

messageHandler := MessageHandler{
    messages: make(map[int]Message),
}

for {
    messageType, message, err := conn.ReadMessage()
    if err != nil {
        log.Println("Read error: ", err)
        break
    }

    // 创建消息对象
    ackChan := make(chan int)
    msg := Message{
        ID:       len(messageHandler.messages) + 1,
        Content:  string(message),
        AckChan:  ackChan,
    }

    // 处理消息
    messageHandler.handleMessage(msg)

    // 等待确认消息
    select {
    case <-ackChan:
        // 收到确认消息
    case <-time.After(time.Second):
        // 消息发送超时，重新发送消息
        conn.WriteMessage(messageType, message)
    }

    // 回复消息
    err = conn.WriteMessage(messageType, message)
    if err != nil {
        log.Println("Write error: ", err)
        break
    }
}

In MessageHandler, we use a map to save messages that have been sent but have not yet received confirmation. When a confirmation message is received, we remove the message from the map.

After the message processing logic is completed, a confirmation message is sent to the sender, and the sender receives the confirmation message through the passed AckChan channel. If no confirmation message is received within a certain period of time, the message will be resent.

3.2 Heartbeat Mechanism
In addition to using the message confirmation mechanism, we can also use the heartbeat mechanism to detect whether the connection is normal.

You can send a heartbeat message to the client regularly. If no reply is received within a period of time, the connection is considered to have been disconnected.

You can define a heartbeat structure:

type Heartbeat struct {
    PingMsg    []byte
    PongMsg    []byte
    Interval   time.Duration
}

func (h *Heartbeat) Start(conn *websocket.Conn) {
    ticker := time.NewTicker(h.Interval)
    defer ticker.Stop()

    for range ticker.C {
        // 发送心跳消息
        err := conn.WriteMessage(websocket.PingMessage, h.PingMsg)
        if err != nil {
            log.Println("Heartbeat error: ", err)
            break
        }

        // 设置心跳超时时间
        conn.SetReadDeadline(time.Now().Add(h.Interval))

        // 等待心跳回复
        _, _, err = conn.ReadMessage()
        if err != nil {
            log.Println("Heartbeat error: ", err)
            break
        }
    }
}

In the handleWebsocket function, we can turn on the heartbeat in the following way:

heartbeat := Heartbeat{
    PingMsg:    []byte("ping"),
    PongMsg:    []byte("pong"),
    Interval:   time.Second * 10,
}

go heartbeat.Start(conn)

In the above code, We use a timer to send heartbeat messages at intervals, then set the heartbeat timeout and wait for the heartbeat reply. If no heartbeat reply is received within a period of time, the connection is considered disconnected.

4. Summary
   This article introduces how to use Go language to develop Websocket applications and deal with message loss issues. By using the message confirmation mechanism and heartbeat mechanism, we can effectively solve the problem of message loss. Of course, depending on the specific business scenario, we can also perform more detailed processing as needed.

By studying this article, you can quickly understand Websocket development in Go language and apply these technologies in actual projects. Hope this article is helpful to you!

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