tcp proxy

tcp-proxy.js

'use strict';

const net = require('net');

function printUsage() {
  console.log('Usage:');
  console.log('  $ node tcp-proxy 3306 remote.ucdok.com 3306');
  process.exit();
}

const port = parseInt(process.argv[2], 10);
if (isNaN(port)) {
  printUsage();
}
const remoteAddr = String(process.argv[3]).trim();
if (!remoteAddr || remoteAddr === 'undefined') {
  printUsage();
}
const remotePort = parseInt(process.argv[4], 10);
if (isNaN(remotePort)) {
  printUsage();
}

function log() {
  process.stdout.write((new Date()).toTimeString() + ' ');
  console.log.apply(console, arguments);
}

function addrInfo(conn) {
  return [ conn.remoteAddress, conn.remotePort ].join(':');
}

const server = net.createServer(conn => {
  log('new client connection:', addrInfo(conn));
  const remote = net.connect(remotePort, remoteAddr, () => {
    log('connected to remote server');
  });
  pipe(conn, remote);
  pipe(remote, conn);
  remote.on('close', () => {
    log('remote closed: ', addrInfo(remote));
    closeAll();
  });
  remote.on('error', err => {
    log('remote error: ', addrInfo(remote), err);
  });
  conn.on('close', () => {
    log('client closed: ', addrInfo(conn));
    closeAll();
  });
  conn.on('error', err => {
    log('client error: ',addrInfo(conn),  err);
    closeAll();
  });
  function closeAll() {
    log('close all: ', addrInfo(conn));
    remote.destroy();
    conn.destroy();
  }
  function pipe(a, b) {
    a.on('data', d => b.write(d));
    a.on('end', () => b.end());
  }
});
server.listen(port, err => {
  console.log('server started: %s => %s:%s', port, remoteAddr, remotePort);
});