exports.findAvailablePort = function (app, callback) {
  var port = null
  try {
    port = Number(fs.readFileSync(path.join(__dirname, '/../.port.tmp')))
  } catch (e) {
    port = Number(process.env.PORT || config.port)
  }
  console.log('')
  // Check that default port is free, else offer to change
  portScanner.findAPortNotInUse(port, port + 50, '127.0.0.1', function (error,availablePort) {
    if (error) { throw error }
    port = availablePort
    fs.writeFileSync(path.join(__dirname, '/../.port.tmp'), port)
    callback(port)
  })
}