node RPC（Remote Procedure Call）

protocol-buffers

https://www.npmjs.com/package/protocol-buffers

buffer

http://nodejs.cn/api/buffer.html#buffer_buf_writebigint64be_value_offset

tcp之单工通信

client和server之间，只能是单向的一方向另一方发送数据。

// client.js
const net = require('net');
const socket = new net.Socket();
socket.connect({port:2000});
process.stdin.on('data',e=>{
    socket.write(Buffer.from([1,2,3]));
})
//server.js
const net = require('net');
net.createServer((socket) => {
    socket.on('data',data=>{
      console.log('server,',data,data.toString());
    })
  }).listen(2000,()=>{
    console.log('server is running')
  })

tcp之半双工通信

client和server，有来有往，如client发送一条消息，收到server响应后，才能发送下一条消息。

//client.js
const net = require('net');
const socket = new net.Socket();
socket.connect({port:2000});
let count = 0;
socket.write(Buffer.from(level()+''));
socket.on('data',data=>{
    console.log('client,',data,data.toString());
    count++;
    if(count<10){
        socket.write(Buffer.from(level()+''));
    }
})
function level(){return Math.floor(Math.random()*(6-1+1))+1};
//server.js
const net = require('net');
net.createServer((socket) => {
    socket.on('data',data=>{
      console.log('server,',data,data.toString());
      if(data){
        socket.write('response');
      }
    })
  }).listen(2000,()=>{
    console.log('server is running')
  })

tcp之全双工通信

client不停的发送请求，不需等到结果就可以发送下一个请求（需要有一个标识，来匹配请求和响应）
在一秒之内，server随机时间返回数据，来混淆数据包的顺序

//client.js
const net = require('net');
const socket = new net.Socket();
socket.connect({port:2000});
function send(num){
    const buf = Buffer.allocUnsafe(2);
    buf.write(num+'', 0); //请求标识
    buf.write(level()+'', 1); //发送的消息
    socket.write(buf);
}
socket.on('data',data=>{
    console.log('client,',data.slice(1).toString(),data.slice(0,1).toString());
})
for(let i=0;i<10;i++){
    setTimeout(()=>{
        send(i);
    },i*2*100)
}
function level(){return Math.floor(Math.random()*(6-1+1))+1};
//server.js
const net = require('net');
net.createServer((socket) => {
    socket.on('data',data=>{
      console.log('server,',data.slice(1).toString(),data.slice(0,1).toString());
      if(data){
        socket.write('response');
        setTimeout(()=>{
          const buf = Buffer.allocUnsafe(4);
          buf.write(data.slice(0,1).toString(),0);
          buf.write(obj[data.slice(1).toString()]||"",1);
          socket.write(buf);
        },10+Math.random()*1000)
      }
    })
  }).listen(2000,()=>{
    console.log('server is running')
  })

  const obj = {
    0:'000',
    1:'111',
    2:'222',
    3:'333',
    4:'444',
    5:'555',
    6:'666',
    7:'777',
    8:'888',
    9:'999'
  }