服务端主动发送数据回客户端在H5里的实现步奏

程序员文章站 2022-03-16 15:30:20

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我们知道，在Server Sent Event里，通过EventSource对象接收服务器发送事件的通知是有三个事件的，message, open, error这三种，今天就给大家演示一下服务端主动发送数据回客户端在H5里的实现步奏。

Server Sent Event

Server Sent Event通过EventSource对象接收服务器发送事件的通知. 有三个事件message, open, error

下面的代码演示了使用的方法

例子代码运行环境: node.js

代码

粘贴下面代码运行node index.js

//index.html
<!DOCTYPE html>
<html>
<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>server-sent</title>
</head>
<body>
  <script>
    window.addEventListener("load",function () {
      let status = document.getElementById("status");
      let output = document.getElementById("output");
      let source;
 
      function connect() {
        source = new EventSource("stream");//与服务器端建立连接
        //鉴定message事件, 获取服务端发送的数据
        source.addEventListener("message", function (event) {
          output.textContent = event.data;
        }, false);
        //监听open事件, 判断连接是否进行中
        source,addEventListener("open", function (event) {
          status.textContent = '连接打开了';
        },false);
        //监听error事件, 处理连接错误的情况
        source.addEventListener("error", function (event) {
          if (event.target.readyState === EventSource.CLOSED) {
            source.close();
            status.textContent = '连接关闭了';
          } else {
            status.textContent = "连接关闭了!未知错误!";
          }
        }, false);
      }
      if(!!window.EventSource) {
        connect();
      } else {
        status.textContent = "不支持server-sent"
      }
    },false);
  </script>
  <span id="status">Connection closed!</span>
  <br>
  <span id="output"></span>
</body>
</html>

服务端代码

//index.js
const http = require('http');
const fs = require('fs');
http.createServer(function (req, res) {
  let interval,
      fileName,
      index = "./index.html";
  console.log(req.url);
  if(req.url === "/") {
    fileName = index;
  } else {
    fileName = "." + req.url;
  }
 
  if (fileName === "./stream") {//如果server sent event则设置相应头信息
    res.writeHead(200, {
      "Content-Type" : "text/event-stream",
      "Cache-Control" : "no-cache",
      "Connection": "keep-alive",
    })
    res.write("retry: 10000\n");//过10000秒重试
    res.write("data: " + (new Date()) + "\n\n");
    interval = setInterval(function () {
      res.write("data: " + (new Date()) + "\n\n");
    }, 1000);
    //监听close事件, 用于停止定时器
    req.connection.addListener("close", function () {
      clearInterval(interval);
    }, false);
  } else if (fileName === index) {
    //判断是否为页面请求, 并找到相应文件返回页面
    fs.exists(fileName, function (exists) {
      if (exists) {
        fs.readFile(fileName, function (error, content) {
          if (error) {
            res.writeHead(500);
            res.end();
          } else {
            res.writeHead(200, {"Content-Type" : "text/html"});
            res.end(content, "utf-8");
          }
        })
      } else {
        console.log(123);
        res.writeHead(404);
        res.end();
      }
    })
  } else {
    res.writeHead(404);
    res.end();
  }
}).listen(8080, "127.0.0.1");
console.log("at 8080");

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