I am looking for a way to communicate with RS232 serial COM port on windows. I have found 2 solutions on the net, which is not totally free (introduces deliberate delays on the function) and with limited capability on Windows. The latter can only write to a COM port on Windows, not read. Theme For Windows Xp Dark Edition here. I can't look at the code of the first solution since it is compiled into a.dll (makes sense, otherwise people can just edit the delay and not purchase it.) and the second one seems only to use fopen() to open the port and later fwrite() to it for writing, just like one would do to a stream. But apparently freading it returns nothing. I know it's possible as the first solution did it, although it does require Apache to use php-cgi module instead of php5module. Another option is to use an object via ActiveX on windows.

This class can be used to communicate with a serial port under Linux or Windows. PHP Serial: Communicate with a serial port. Of my PHP Serial Class page. This class can be used to communicate with a serial port under Linux or Windows. It takes the path (like '/dev/ttyS0' for linux or 'COM1' for windows) of serial.

There are several, mostly commercial serial objects for COM on windows. You can also expose a.Net based object and register it for COM use as well. Of course, this does presume you have control on the server to register a COM control, as you would need a serial interface. Another issue is resource contention if this is for use via the Web. If this is for a serial printer, for instance, then a print queue manager would be your best option over direct communication.