I don't understand what you've got here. Your example program only has a single serial port init so only one port at a time can be initialized and only a single port at a time can be written to and read from. Or are you attempting to call this VI as a subVI twice in a main program?
Yes I am calling this program multiple times throughout the program and sometimes I write to com 1 and sometimes to com 0. I have recently made this work by closeing and reinitializing the port after each communication
And if you want simultaneous communication, I suggest you use VISA instead of the old serial drivers and set the VISA Read/Write for asynchronous. The old serial drivers are no longer supported by NI and are gone in LabVIEW 7.
