全双工通信

nodejs，net模块
单工
半双工的通信通道搭建
发送，然后登台接收，然后再发送

socket 套接字通信
交换机通信
web通信技术 https://zhuanlan.zhihu.com/p/21573180

轮询，每个一秒钟请求一次服务器，例如 定时器
长轮询

全双工通信的关键

• 在于应用层协议，需要有标记包段的信号
• 处理一下情况，需要有标记包长的字段
  • 粘包
  • 不完整包
• 错误处理

server

const net = require('net');
const server = net.createServer((socket) => {
    socket.on('data', function(buffer) {
        console.log(buffer);
        const seqBuffer = buffer.slice(0, 2);
        const lessonid = buffer.readInt32BE(2);
        setTimeout(()=> {
            // console.log(data[lessonid])
            const buffer = Buffer.concat([
                seqBuffer,
                Buffer.from(data[lessonid])
            ])
            socket.write(
                buffer
            );
        }, 10 + Math.random() * 1000)
    })
});
server.listen(4000);
const data = {
    136797: "01 | 课程介绍",
    136798: "02 | 内容综述",
    136799: "03 | Node.js是什么？",
    136800: "04 | Node.js可以用来做什么？",
    136801: "05 | 课程实战项目介绍",
    136803: "06 | 什么是技术预研？",
    136804: "07 | Node.js开发环境安装",
    136806: "08 | 第一个Node.js程序：石头剪刀布游戏",
    136807: "09 | 模块：CommonJS规范",
    136808: "10 | 模块：使用模块规范改造石头剪刀布游戏",
    136809: "11 | 模块：npm",
    141994: "12 | 模块：Node.js内置模块",
    143517: "13 | 异步：非阻塞I/O",
    143557: "14 | 异步：异步编程之callback",
    143564: "15 | 异步：事件循环",
    143644: "16 | 异步：异步编程之Promise",
    146470: "17 | 异步：异步编程之async/await",
    146569: "18 | HTTP：什么是HTTP服务器？",
    146582: "19 | HTTP：简单实现一个HTTP服务器"
}

client

const net = require('net');
const socket = new net.Socket({});
socket.connect({
    host: '127.0.0.1',
    port: 4000
});
const lessonids = [
    "136797",
    "136798",
    "136799",
    "136800",
    "136801",
    "136803",
    "136804",
    "136806",
    "136807",
    "136808",
    "136809",
    "141994",
    "143517",
    "143557",
    "143564",
    "143644",
    "146470",
    "146569",
    "146582"
]
let id = Math.floor(Math.random() * lessonids.length);
socket.on('data', (buffer) => {
    const seqBuffer = buffer.slice(0, 2);
    const titleBuffer = buffer.slice(2);
    console.log(seqBuffer.readInt16BE(), titleBuffer.toString())
})
let seq = 0;
function encode(index) {
    buffer = Buffer.alloc(6);
    buffer.writeInt16BE(seq)
    buffer.writeInt32BE(
        lessonids[index], 2
    );
    console.log(seq, lessonids[index]);
    seq++;
    return buffer;
}
for (let k = 0; k < 100; k++) {
    id = Math.floor(Math.random() * lessonids.length);
    socket.write(encode(id));
}