code: function () {
                              libra.pop();
                              // if logging is active, emit 'reply'
                              if ( elen ) me.emit( err_reply ? 'error-reply' : 'reply', cmd, data, cmd.fn || fn );
                              // execute callback
                              cmd.zn( err_reply, data, cmd.fn );
                              // check if the client is quitting connection
                              return cmd.isQuit ? cocker.bye() : null;
                          }
docs: get queue head