I am developing one software for managing parking lot. System is designed to use four HID RFID devices for authorization clients on gates. Each device should be connected to server by Serial port RS232. Now I wondering is there some device or method to join all that devices on one device and after that to I have only one RS232 cable connected to server. My problem is in that RFID card readers are simple (stupid) devices and there I am not able to change anything, but Ill like to know from which specific device is coming input. What Ill want to do with that new device which need to join four readers is to add suffix or prefix to string that sent from RFID card reader. So I can identify device that is sending card number to my server. I am developing my system on Win platforms.