1. 封装websocket
1.1.1. 协议
websocket是个二进制协议，需要先通过Http协议进行握手，从而协商完成从Http协议向websocket协议的转换。一旦握手结束，当前的TCP连接后续将采用二进制websocket协议进行双向双工交互，自此与Http协议无关。
可以通过这篇知乎了解一下websocket协议的基本原理：《WebSocket 是什么原理？为什么可以实现持久连接？》。
下面代码是封装的websocket
目录结构：
-impl
--connection.go
-main.go
-client.html
connection.go文件代码
package impl
import (
"errors"
"sync"
"github.com/gorilla/websocket"
)
type Connection struct {
wsConn *websocket.Conn
//读取websocket的channel
inChan chan []byte
//给websocket写消息的channel
outChan chan []byte
closeChan chan byte
mutex sync.Mutex
//closeChan 状态
isClosed bool
}
//初始化长连接
func InitConnection(wsConn *websocket.Conn) (conn *Connection, err error) {
conn = &Connection{
wsConn: wsConn,
inChan: make(chan []byte, 1000),
outChan: make(chan []byte, 1000),
closeChan: make(chan byte, 1),
}
//启动读协程
go conn.readLoop()
//启动写协程
go conn.writeLoop()
return
}
//读取websocket消息
func (conn *Connection) ReadMessage() (data []byte, err error) {
select {
case data = <-conn.inChan:
case <-conn.closeChan:
err = errors.New("connection is closed")
}
return
}
//发送消息到websocket
func (conn *Connection) WriteMessage(data []byte) (err error) {
select {
case conn.outChan <- data:
case <-conn.closeChan:
err = errors.New("connection is closed")
}
return
}
//关闭连接
func (conn *Connection) Close() {
//线程安全的Close,可重入
conn.wsConn.Close()
//只执行一次
conn.mutex.Lock()
if !conn.isClosed {
close(conn.closeChan)
conn.isClosed = true
}
conn.mutex.Unlock()
}
func (conn *Connection) readLoop() {
var (
data []byte
err error
)
for {
if _, data, err = conn.wsConn.ReadMessage(); err != nil {
goto ERR
}
//如果数据量过大阻塞在这里,等待inChan有空闲的位置！
select {
case conn.inChan <- data:
case <-conn.closeChan:
//closeChan关闭的时候
goto ERR
}
}
ERR:
conn.Close()
}
func (conn *Connection) writeLoop() {
var (
data []byte
err error
)
for {
select {
case data = <-conn.outChan:
case <-conn.closeChan:
goto ERR
}
if err = conn.wsConn.WriteMessage(websocket.TextMessage, data); err != nil {
goto ERR
}
}
ERR:
conn.Close()
}
main.go文件代码
package main
import (
"net/http"
"time"
"github.com/gorilla/websocket"
"github.com/student/1330/impl"
)
var (
upgrade = websocket.Upgrader{
//允许跨域
CheckOrigin: func(r *http.Request) bool {
return true
},
}
)
func wsHandler(w http.ResponseWriter, r *http.Request) {
var (
//websocket 长连接
wsConn *websocket.Conn
err error
conn *impl.Connection
data []byte
)
//header中添加Upgrade:websocket
if wsConn, err = upgrade.Upgrade(w, r, nil); err != nil {
return
}
if conn, err = impl.InitConnection(wsConn); err != nil {
goto ERR
}
go func() {
var (
err error
)
for {
if err = conn.WriteMessage([]byte("heartbeat")); err != nil {
return
}
time.Sleep(time.Second * 1)
}
}()
for {
if data, err = conn.ReadMessage(); err != nil {
goto ERR
}
if err = conn.WriteMessage(data); err != nil {
goto ERR
}
}
ERR:
conn.Close()
}
func main() {
//http标准库
http.HandleFunc("/ws", wsHandler)
http.ListenAndServe("0.0.0.0:5555", nil)
}
client.html文件代码
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script>
window.addEventListener("load", function(evt) {
var output = document.getElementById("output");
var input = document.getElementById("input");
var ws;
var print = function(message) {
var d = document.createElement("div");
d.innerHTML = message;
output.appendChild(d);
};
document.getElementById("open").onclick = function(evt) {
if (ws) {
return false;
}
ws = new WebSocket("ws://localhost:5555/ws");
ws.onopen = function(evt) {
print("OPEN");
}
ws.onclose = function(evt) {
print("CLOSE");
ws = null;
}
ws.onmessage = function(evt) {
print("RESPONSE: " + evt.data);
}
ws.onerror = function(evt) {
print("ERROR: " + evt.data);
}
return false;
};
document.getElementById("send").onclick = function(evt) {
if (!ws) {
return false;
}
print("SEND: " + input.value);
ws.send(input.value);
return false;
};
document.getElementById("close").onclick = function(evt) {
if (!ws) {
return false;
}
ws.close();
return false;
};
});
</script>
</head>
<body>
<table>
<tr><td valign="top" width="50%">
<p>Click "Open" to create a connection to the server,
"Send" to send a message to the server and "Close" to close the connection.
You can change the message and send multiple times.
</p>
<form>
<button id="open">Open</button>
<button id="close">Close</button>
<input id="input" type="text" value="Hello world!">
<button id="send">Send</button>
</form>
</td><td valign="top" width="50%">
<div id="output"></div>
</td></tr></table>
</body>
</html>