Error 63 With the Host VI Generated by the Communication Wizard

Updated Jun 13, 2024

Reported In


  • LabVIEW Full
  • LabVIEW Professional
  • LabVIEW Real-Time Module

Operating System

  • Windows

Issue Details

When running the Host VI that was generated by the Communication Wizard, why do I see this error?

Error 63 occurred at TCP Open Connection in

Possible reason(s):
LabVIEW: Serial port receive buffer overflow.
LabVIEW: The network connection was refused by the server.


Error 63 at TCP Open Connection means either that the server refused the connection or that the server hasn't been started.

If you are building the VIs into executables, be sure to build the Normal Priority Loop VI (NPL) as a Source VI with the Time Critical Loop VI (TCL) as a Dynamic VI (see screenshot below).

If you are not building the VIs into executables, then follow these steps:
  1. Check to make sure that the TCP server is running on your target before you connect to it using the Host VI. In the case of running the VIs generated by the Communication Wizard, the VIs for the server are located in the NPL VI. In this VI you will find the Create Listener and Wait Listener VIs. So make sure that you first target to the RT controller and run the NPL. This VI will call the TCL VI and will set the TCP server ready for connections.
  2. After the NPL is running then go to Operate┬╗Switch Target┬╗LabVIEW for Windows.
  3. Run the Host VI.

If that doesn't fix the problem and you have XP SP2, then ensure that your Firewall is disabled.