Hi Pari
Check your labview.ini file for a line like:-
serialDevices="COM1;COM2;LPT1;
In this example you would refer to LPT1 as port 2 or ASRL2 because it is #2 in the list (COM1 is 0th, COM1 is 1st, LPT1 is 2nd)
If the program is a .exe then it will need its own .ini file e.g fred.exe will need a fred.ini file
Hope this helps
Keith