A basic TCP proxy written in node.js with dynamic remote host

tcpproxy.js

#!/usr/bin/env node
const net = require('net');

process.on('uncaughtException', function(error) {
  console.error(error);
});

const localPortHttp  = process.argv[2];
const localPortHttps = process.argv[3];

let server = net.createServer(function(localsocket) {
  const remoteSocket = new net.Socket();
  const obj = { count: 0 };

  // remoteSocket.connect(remotePort, remoteHost);

  localsocket.on('connect', function(data) {
    console.log('>>> connection #%d from %s:%d',
      server.connections,
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
  });

  localsocket.on('data', function(data) {
    console.log('%s:%d - writing data to remote',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    if (obj.count === 0) {
      let host = data.toString().replace(/\r?\n|\r/g, " ").split(":")[1].split(" ")[1];
      remoteSocket.connect(localPortHttp, host);
      obj.count++;
    }

    let flushed = remoteSocket.write(data);
    if (!flushed) {
      console.log('  remote not flushed; pausing local');
      localsocket.pause();
    }
  });

  remoteSocket.on('data', function(data) {
    console.log('%s:%d - writing data to local',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    console.log('send to local:', data.toString());
    let flushed = localsocket.write(data);
    if (!flushed) {
      console.log('  local not flushed; pausing remote');
      remoteSocket.pause();
    }
  });

  localsocket.on('drain', function() {
    console.log('%s:%d - resuming remote',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    remoteSocket.resume();
  });

  remoteSocket.on('drain', function() {
    console.log('%s:%d - resuming local',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    localsocket.resume();
  });

  localsocket.on('close', function(had_error) {
    console.log('%s:%d - closing remote',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    remoteSocket.end();
  });

  remoteSocket.on('close', function(had_error) {
    console.log('%s:%d - closing local',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    localsocket.end();
  });

});

let serverHttps = net.createServer(function(localsocket) {
  const remoteSocket = new net.Socket();
  const obj = { count: 0 };

  localsocket.on('connect', function(data) {
    console.log('>>> connection #%d from %s:%d',
      server.connections,
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
  });

  localsocket.on('data', function(data) {
    console.log('%s:%d - writing data to remote',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    if (obj.count === 0) {
      let host = data.toString().replace(/[^\x20-\x7E]/g, '').replace(/[^.,1-9a-z ]/g, ' ').split(' ');
      host = longest_string(host);
      remoteSocket.connect(localPortHttps, host[0]);
      obj.count++;
    }

    let flushed = remoteSocket.write(data);
    if (!flushed) {
      console.log('  remote not flushed; pausing local');
      localsocket.pause();
    }
  });

  remoteSocket.on('data', function(data) {
    console.log('%s:%d - writing data to local',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    console.log('send to local:', data.toString());
    let flushed = localsocket.write(data);
    if (!flushed) {
      console.log('  local not flushed; pausing remote');
      remoteSocket.pause();
    }
  });

  localsocket.on('drain', function() {
    console.log('%s:%d - resuming remote',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    remoteSocket.resume();
  });

  remoteSocket.on('drain', function() {
    console.log('%s:%d - resuming local',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    localsocket.resume();
  });

  localsocket.on('close', function(had_error) {
    console.log('%s:%d - closing remote',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    remoteSocket.end();
  });

  remoteSocket.on('close', function(had_error) {
    console.log('%s:%d - closing local',
      localsocket.remoteAddress,
      localsocket.remotePort,
    );
    localsocket.end();
  });

});


function longest_string(str_ara) {
  var max = str_ara[0].length;
  str_ara.map(v => max = Math.max(max, v.length));
  result = str_ara.filter(v => v.length == max);
  return result;
}

server.listen(localPortHttp  , '0.0.0.0');
serverHttps.listen(localPortHttps , '0.0.0.0');

console.log('redirecting connections from 0.0.0.0:%d and 0.0.0.0:%s', localPortHttp , localPortHttps);


// For running the proxy execute this:
// ./proxy.js 80 443
// This would run proxy on port 80 and 443