   How to write a custom com port driver?
  Hello,I have a micro controller that has a few com ports and I connect to it via tcpip through a specialized software interface. I want to create a windows driver so that I can send data to it like a regular com port. Unfortunately, all out-going data needs to be tagged so the micro-controller knows what ports to send the data to.I've bene looking all over but I cannot find any information on how to write such a driver.Any info would be greatly appreciated.   
  Well, since you say you've found nothing I'll assume you need the MS DDK from here. Beyond that all I can say is from what I've heard about driver programming expect it to be messy.   ;  If your hardware needs a serial (COM) port interface, you're better off using that. For PC's that don't have COM ports (typically laptops) alternatives include custom bridging hardware (USB to serial dongles) or as you mentioned TCP/IPCustom TCP/IP stacks for small microcontrollers are readily available. Google around, you should be able to find at least one for the ATMEL series. Once you get TCP working to intermediate hardware you can then use the serial interface of that chip to hook into your hardware.If at all possible avoid using the DDK - there are plenty of alternatives.   