Wrapper for net.connect to test if a host can be connected to on a given tcp port

test-connect.js

'use strict';

var fmt = require('util').format;
var net = require('net');

module.exports = testConnection;

if (require.main !== module) {
  return;
}

var host = process.argv[2];
var port = 1 * (process.argv[3] || 80);
var timeout = 1 * (process.argv[4] || 5);

if (timeout < 100) {
  // assume given in seconds
  timeout = timeout * 1000;
}

testConnection(host, port, timeout, console.log);

function testConnection(host, port, timeout, callback) {
  var failure = new Error(fmt('could not connect to: %s:%d within %dms',
                              host, port, timeout));
  var timer = setTimeout(failed, timeout);
  var so = net.connect(port, host, connected);
  so.setTimeout(timeout, failed);
  so.once('error', failed);
  return so;

  function cleanup() {
    if (!so) {
      return false;
    }
    clearTimeout(timer);
    so.end();
    so.destroy();
    so.unref();
    so = null;
    return true;
  }

  function connected() {
    if (cleanup()) {
      callback(null, true);
    }
  }

  function failed(err) {
    if (cleanup()) {
      callback(err || failure);
    }
  }
}