Error 6101 in Modbus Library MB Serial Example

Updated Jan 18, 2023

Reported In


  • CompactRIO Chassis


  • LabVIEW Datalogging and Supervisory Control Module




Modbus Library, 

Issue Details

I have installed the Modbus LabVIEW Library but when I run "MB Serial Example" I get Error 6101.


Error 6101 is a timeout error and it is caused by the failure of the communication between the client and the server.

If you experience this error, please ensure you have all the below stated points implemented:
  • The MB Serial Example must be started before the MB Serial Example;
  • The COM Ports must be connected using a null modem cable. Moreover the cable must match the communication protocol of the hardware (for example if the hardware has a RS-485 port, be sure that the cable is RS-485 compliant).  
  • One of the COM Ports is not working properly. In order to verify that a serial port is operational, you can perform a serial loopback test: further details can be found in the "How to Do a Serial Loopback Test" tutorial linked below. There are also some free utilities that can be used to check the functionality of COM ports, as for example Portmon for Windows.
  • Ensure that the cable is properly secured and that the Modbus wiring is correct (based on your cable connection type)