# RS-232 and Multithreading

You can call RS-232 Library functions from different threads in the same process, even if the functions operate on the same port. The following limitations apply:

- Do not use the rs232err global variable in a multithreaded application. Use ReturnRS232Err instead.
- Do not call XModemReceive or ComToFile from two threads at the same time if the target file in both calls is the Standard Output.