只要动手做起来，多投入时间和精力、耐心去研究，以大多人的智商加google，平时遇到的大部分问题我们都是可以自己解决的，大部分的知识我们都是可以掌握的。
我们都知道http协议是单向请求的，无法实现双向通信，它只能从客户端发送请求，然后服务端再响应请求，无法做到服务端主动向客户端去推送消息。
尽管可以通过setTimeout/setInterval轮询的方式来不断去刷新获取服务端的数据，但是轮询的效率低，非常浪费资源。webscoket就是为了解决这一问题而存在的。
webscoket的特点：
1、建立在Tcp协议之上
2、与http协议有着很好的兼容性
3、通信高效，因为它的数据格式比较轻量、性能开销小
4、可以发送文本和二进制数据
5、没有同源限制
6、协议标识符是ws
简单的通信原理如下
客户端的实现：
浏览器端的实现
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>WebSocket</title>
</head>
<body>
<h1>Echo Test</h1>
<input id="sendTxt" type="text"/>
<button id="sendBtn">发送</button>
<div id="recv"></div>
<script type="text/javascript">
var WebSocket = new WebSocket("ws://localhost:8080");
WebSocket.onopen = function(){
console.log('websocket open');
document.getElementById("recv").innerHTML = "Connected";
}
WebSocket.onclose = function(){
console.log('websocket close');
}
WebSocket.onmessage = function(e){
console.log(e.data);
document.getElementById("recv").innerHTML = e.data;
}
document.getElementById("sendBtn").onclick = function(){
var txt = document.getElementById("sendTxt").value;
WebSocket.send(txt);
}
</script>
</body>
</html>
服务端实现：
nodejs搭建服务器，可以参考git上的《一起学nodejs》搭建服务器
文件目录下 npm install webscoket
var WebSocketServer = require('websocket').server;
var http = require('http');
var server = http.createServer(function(request, response) {
console.log((new Date()) + ' Received request for ' + request.url);
response.writeHead(404);
response.end();
});
server.listen(8080, function() {
console.log((new Date()) + ' Server is listening on port 8080');
});
wsServer = new WebSocketServer({
httpServer: server,
// You should not use autoAcceptConnections for production
// applications, as it defeats all standard cross-origin protection
// facilities built into the protocol and the browser. You should
// *always* verify the connection's origin and decide whether or not
// to accept it.
autoAcceptConnections: false
});
function originIsAllowed(origin) {
// put logic here to detect whether the specified origin is allowed.
return true;
}
wsServer.on('request', function(request) {
if (!originIsAllowed(request.origin)) {
// Make sure we only accept requests from an allowed origin
request.reject();
console.log((new Date()) + ' Connection from origin ' + request.origin + ' rejected.');
return;
}
var connection = request.accept('', request.origin);
console.log((new Date()) + ' Connection accepted.');
connection.on('message', function(message) {
if (message.type === 'utf8') {
console.log('Received Message: ' + message.utf8Data);
connection.sendUTF(message.utf8Data);
}
else if (message.type === 'binary') {
console.log('Received Binary Message of ' + message.binaryData.length + ' bytes');
connection.sendBytes(message.binaryData);
}
});
connection.on('close', function(reasonCode, description) {
console.log((new Date()) + ' Peer ' + connection.remoteAddress + ' disconnected.');
});
});
参考资料：
客户端（浏览器端）实现参考阮一峰：http://www.ruanyifeng.com/blog/2017/05/websocket.html
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