tcp-proxy-receiver.js

var net = require('net');
var listener = net.createServer();
var port = process.env.PORT || 6980;
var sendNack = !!process.env.SEND_NACK;
var startBlock = String.fromCharCode(0x0B);
var endBlock = String.fromCharCode(0x1C, 0x0D);

listener.on('connection', function (socket) {

  function printEventMessage(event) {
    console.log(event);
  }

  socket.on('end', function () {
    printEventMessage('end');
  });

  socket.on('close', function () {
    printEventMessage('close');
  });

  var buffer = '';
  socket.on('error', function (err) {
    printEventMessage('error');
    console.log(err);
  });

  socket.on('data', function (data) {
    printEventMessage('data');
    console.log(data.toString());
    var ack = startBlock;
    if (sendNack) {
      ack = ack + 'MSH|^~\\&|REDOX|RDX|||20161130174746||ACK||P|2.3\rMSA|AE';
      //ack = ack + 'MSH|^~\\&\nMSA|AE';
    } else {
      ack = ack + 'MSH|^~\\&|REDOX|RDX|||20161130174746||ACK||P|2.3\rMSA|AA';
      //ack = ack + 'MSH|^~\\&\nMSA|AA';
    }

    ack = ack + endBlock;

    setTimeout(function () {
      socket.write(ack);
    }, 4000);
  });
});

listener.on('error', function (err) {
  console.error('Error in MLLP listener. Error: ' + err.code);
});

listener.on('close', function () {
  console.log('Closed connection on port ' + port);
});

listener.listen(port, function () {

  console.log('Listening on port ' + port);
});