code: function _handleMEI(requestBuffer, vector, unitID, callback) {
      var MEIType = requestBuffer[2];
      switch(parseInt(MEIType)) {
          case 14:
              _handleReadDeviceIdentification(requestBuffer, vector, unitID, callback);
              break;
          default:
              callback({ modbusErrorCode: 0x01 }); // illegal MEI type
      }
  }
docs: Function to handle FC43 request.
  
  @param requestBuffer - request Buffer from client
  @param vector - vector of functions for read and write
  @param unitID - Id of the requesting unit
  @param {function} callback - callback to be invoked passing {Buffer} response
  @returns undefined
  @private