code: function disconnect() {
    var force = arguments.length <= 0 || arguments[0] === undefined ? false : arguments[0];
    var cb = arguments.length <= 1 || arguments[1] === undefined ? undefined : arguments[1];
  
    console.log('Disconnecting client: ' + clientId);
    stopPub = true;
    client.end(force, cb);
  }
docs: disconnect disconnect from the broker
  @param  {Boolean}  force force disconnect. Default: false
  @param  {Function} cb    Callback function the be called after disconnect. Default: undefined