The port driver reads the initialization data from the INI file, interprets the data, and issues the appropriate DosDevIOCtl calls to the open port given by the file handle.

This function is called from the spooler function, PrtOpen, to complete port opening. Note that PrtOpen issues the actual DosOpen first. PrtOpen holds a semaphore for each port in use, and a linked list of threads waiting on the semaphore because, although the spooler serializes output, it is still possible for applications to write directly to the port by using DevOpenDC (OD_DIRECT).