code: function sendMessageOnce( oWs, sCommand, jsonMessage )
  {
  	//	...
  	sendMessage( oWs, sCommand, jsonMessage );
  
  	//	...
  	let nCheckInterval = setInterval( () =>
  	{
  		if ( 0 === oWs.bufferedAmount )
  		{
  			//	Im' not busy anymore - set a flag or something like that
  			clearInterval( nCheckInterval );
  			nCheckInterval = null;
  
  			//	close socket
  			oWs.close( 1000, 'done' );
  		}
  	}, 50 );
  }
docs: send message and then close the socket
  
  @public
  @param	{object}	oWs
  @param	{string}	sCommand
  @param	{object}	jsonMessage
  @return {boolean}