Go如何实现Websocket服务以及代理

# 升级为 websocket
Upgrade: websocket
Connection: Upgrade
# 一个 Base64 encode 的值，有于验证服务器端是否支持websocket
Sec-WebSocket-Key: x4JJHMbDL22zLk1GBhXDw==
# 用户协议，可以视为不同业务逻辑的频道
Sec-WebSocket-Protocol: chat
# 协议版本，13是当前通用版本，几乎不需要更改
Sec-WebSocket-Version: 13

HTTP/1.1 101 Switching Protocols
# 协议升级
Upgrade: websocket
# 连接状态
Connection: Upgrade
# WebSocket服务端根据Sec-WebSocket-Key生成
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
# WebSocket协议用户协议
Sec-WebSocket-Protocol: chat

func WebSocketServer() {
	addr := "localhost:8002"
	http.HandleFunc("/wshandler", WebSocketUpgrade)
	log.Println("Starting websocket server at " + addr)

	go func() {
		err := http.ListenAndServe(addr, nil)
		if err != nil {
			log.Fatal(err)
		}
	}()

	log.Println("WebSocket 服务器正在运行。按Ctrl+C退出")
	select {}
}

func WebSocketUpgrade(resp http.ResponseWriter, req *http.Request) {
	// 初始化 Upgrader
	upgrader := websocket.Upgrader{} // 使用默认的选项
	// 第三个参数是响应头,默认会初始化
	conn, err := upgrader.Upgrade(resp, req, nil)
	if err != nil {
		log.Println(err)
		return
	}
	defer conn.Close()

	// 读取客户端的发送额消息,并返回
	go ReadMessage(conn)
	select {}
}

// 读取客户端发送的消息,并返回
func ReadMessage(conn *websocket.Conn) {
	for {
		// 消息类型:文本消息和二进制消息
		messageType, msg, err := conn.ReadMessage()
		if err != nil {
			log.Println(err)
			return
		}
		fmt.Println("receive msg:", string(msg))

		err = conn.WriteMessage(messageType, msg)
		if err != nil {
			log.Println("write error:", err)
			return
		}
	}
}

package websocket

import (
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
)

var (
	// 代理服务器地址
	proxyServer     = "127.0.0.1:8082"
	// 真实websocket服务器地址
	websocketServer = "http://127.0.0.1:8002"
)

func WebSocketProxy() {
	url, err := url.Parse(websocketServer)
	if err != nil {
		log.Println(err)
	}
	proxy := httputil.NewSingleHostReverseProxy(url)
	log.Println("WebSocket 代理启动, 按CTRL+C退出")
	http.ListenAndServe(proxyServer, proxy)
}

websocket 服务器每隔 3 秒会主动向服务器推送消息"Heart Beat"

func WebSocketServer() {
	addr := "localhost:8002"
	http.HandleFunc("/wshandler", WebSocketUpgrade)
	log.Println("Starting websocket server at " + addr)

	go func() {
		err := http.ListenAndServe(addr, nil)
		if err != nil {
			log.Fatal(err)
		}
	}()

	log.Println("WebSocket 服务器正在运行。按Ctrl+C退出")
	select {}
}

func WebSocketUpgrade(resp http.ResponseWriter, req *http.Request) {
	// 初始化 Upgrader
	upgrader := websocket.Upgrader{} // 使用默认的选项
	// 第三个参数是响应头,默认会初始化
	conn, err := upgrader.Upgrade(resp, req, nil)
	if err != nil {
		log.Println(err)
		return
	}
	defer conn.Close()

	// 主动向服务端推送消息
	go PushMessage(conn)

	// 读取客户端的发送额消息,并返回
	go ReadMessage(conn)
	select {}
}

// websocket 服务器主动服务器推送消息
func PushMessage(conn *websocket.Conn) {
	for {
		err := conn.WriteMessage(websocket.TextMessage, []byte("heart beat"))
		if err != nil {
			log.Println(err)
			return
		}
		time.Sleep(time.Second * 3)
	}
}

// 读取客户端发送的消息,并返回
func ReadMessage(conn *websocket.Conn) {
	for {
		// 消息类型:文本消息和二进制消息
		messageType, msg, err := conn.ReadMessage()
		if err != nil {
			log.Println(err)
			return
		}
		fmt.Println("receive msg:", string(msg))

		err = conn.WriteMessage(messageType, msg)
		if err != nil {
			log.Println("write error:", err)
			return
		}
	}
}