# 升級(jí)為 websocket
Upgrade: websocket
Connection: Upgrade
# 一個(gè) Base64 encode 的值，有于驗(yàn)證服務(wù)器端是否支持websocket
Sec-WebSocket-Key: x4JJHMbDL22zLk1GBhXDw==
# 用戶協(xié)議，可以視為不同業(yè)務(wù)邏輯的頻道
Sec-WebSocket-Protocol: chat
# 協(xié)議版本，13是當(dāng)前通用版本，幾乎不需要更改
Sec-WebSocket-Version: 13

HTTP/1.1 101 Switching Protocols
# 協(xié)議升級(jí)
Upgrade: websocket
# 連接狀態(tài)
Connection: Upgrade
# WebSocket服務(wù)端根據(jù)Sec-WebSocket-Key生成
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
# WebSocket協(xié)議用戶協(xié)議
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 服務(wù)器正在運(yùn)行。按Ctrl+C退出")
	select {}
}

func WebSocketUpgrade(resp http.ResponseWriter, req *http.Request) {
	// 初始化 Upgrader
	upgrader := websocket.Upgrader{} // 使用默認(rèn)的選項(xiàng)
	// 第三個(gè)參數(shù)是響應(yīng)頭,默認(rèn)會(huì)初始化
	conn, err := upgrader.Upgrade(resp, req, nil)
	if err != nil {
		log.Println(err)
		return
	}
	defer conn.Close()

	// 讀取客戶端的發(fā)送額消息,并返回
	go ReadMessage(conn)
	select {}
}

// 讀取客戶端發(fā)送的消息,并返回
func ReadMessage(conn *websocket.Conn) {
	for {
		// 消息類(lèi)型:文本消息和二進(jìn)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 (
	// 代理服務(wù)器地址
	proxyServer     = "127.0.0.1:8082"
	// 真實(shí)websocket服務(wù)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 代理啟動(dòng), 按CTRL+C退出")
	http.ListenAndServe(proxyServer, proxy)
}

websocket 服務(wù)器每隔 3 秒會(huì)主動(dòng)向服務(wù)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 服務(wù)器正在運(yùn)行。按Ctrl+C退出")
	select {}
}

func WebSocketUpgrade(resp http.ResponseWriter, req *http.Request) {
	// 初始化 Upgrader
	upgrader := websocket.Upgrader{} // 使用默認(rèn)的選項(xiàng)
	// 第三個(gè)參數(shù)是響應(yīng)頭,默認(rèn)會(huì)初始化
	conn, err := upgrader.Upgrade(resp, req, nil)
	if err != nil {
		log.Println(err)
		return
	}
	defer conn.Close()

	// 主動(dòng)向服務(wù)端推送消息
	go PushMessage(conn)

	// 讀取客戶端的發(fā)送額消息,并返回
	go ReadMessage(conn)
	select {}
}

// websocket 服務(wù)器主動(dòng)服務(wù)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)
	}
}

// 讀取客戶端發(fā)送的消息,并返回
func ReadMessage(conn *websocket.Conn) {
	for {
		// 消息類(lèi)型:文本消息和二進(jìn)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
		}
	}
}