[nodejs] TCP example

tcp-echo.js

"use strict";

const net = require("net");

const port = process.env.PORT || 44444;
const once = !!process.env.ONCE || false;

function echo(socket) {
    const server = this;
    const {remoteAddress, remoteFamily, remotePort} = socket;
    const bufs = [];
    socket.on("data", buf => bufs.push(buf)).once("end", _ => {
        const msg = Buffer.concat(bufs);
        console.log(msg.toString(), {remoteAddress, remoteFamily, remotePort});
        socket.end(Buffer.from(`accept: ${msg.toString()}`));
        if (once) server.close();
    });
};

const server = net.createServer({allowHalfOpen: true}, echo);
server.listen(port, _ => {
    const address = server.address();
    console.log(`listen on`, address);
});

tcp-send.js

"use strict";

const net = require("net");

const host = process.env.HOST || "localhost";
const port = process.env.PORT || 44444;
const msg = process.env.MSG || "Hello TCP";

const addr = {}, bufs = [];
const socket = net.createConnection({allowHalfOpen: true, port, host}, _ => {
    const {remoteAddress, remoteFamily, remotePort} = socket;
    Object.assign(addr, {remoteAddress, remoteFamily, remotePort});
    socket.end(Buffer.from(msg));
}).on("data", buf => bufs.push(buf)).once("end", _ => {
    const msg = Buffer.concat(bufs);
    console.log(msg.toString(), addr);
});

Compare with the UDP code: https://gist.github.com/bellbind/8b4d02adb3672df400280c3a6df68a91

[play on localhost]

server:

PORT=44444 node tcp-echo.js

client:

PORT=44444 MSG="Hello TCP" node tcp-send.js