Wiretap TCP connection

wiretap.js

var net = require('net');
var stream = require('stream');
var util = require('util');

// ANSI colors.
var green = '\u001b[32m';
var yellow = '\u001b[33m';
var reset = '\u001b[0m';

// CLI args.
var host = process.argv[2];
if (!host) {
  console.log('usage: node wiretap.js <host> [<port>]');
  process.exit(1);
}
var port = parseInt(process.argv[3] || '80', 10);

// A transform stream to tap data.
function WireTap(prefix) {
  stream.Transform.call(this, {});
  this.prefix = prefix;
}
util.inherits(WireTap, stream.Transform);
WireTap.prototype._transform = function (chunk, encoding, callback) {
  console.log(this.prefix + "'" + chunk.toString('utf-8') + "'");
  callback(null, chunk);
};

// Server.
var server = net.createServer(function (c) {
  var c2t = new WireTap(green + '> ');
  var t2c = new WireTap(yellow + '< ');

  console.log(reset + '-- client connection started');
  var target = net.connect(port, host, function () {
    console.log(reset + '-- target connection opened');
    c.pipe(c2t).pipe(target);
    target.pipe(t2c).pipe(c);
  });
  target.on('end', function () {
    console.log(reset + '-- target connection closed');
    unpipe();
  });
  c.on('end', function () {
    console.log(reset + '-- client connection closed');
    unpipe();
  });

  function unpipe() {
    c.unpipe(c2t);
    c2t.unpipe(target);
    target.unpipe(t2c);
    t2c.unpipe(c);
  }
});
server.listen(5050, function () {
  console.log('Listening on 5050, proxying to', host + ':' + port);
});