code: function send() {
    var message = arguments.length <= 0 || arguments[0] === undefined ? 'hello mqtt-controls' : arguments[0];
    var topic = arguments.length <= 1 || arguments[1] === undefined ? null : arguments[1];
  
    var t = undefined;
    if (topic === null) {
      t = topics.publish;
    } else {
      t = topic;
    }
    client.publish(t, message);
  }
docs: Send one signal to the borker
  @param  {String} message - The message to send. Default: `{'hello mqtt-controls'}`
  @param  {String} topic - The topic to send to. Default: is `topics = {'subscribe':'/output/#','publih':'/input/'}`