Can I get a linux system to listen for data on a serial port and then validate it?

Hi!

We have a very ancient Parking system running on an NT server. We encode our guests keys for their hotel room on magnetic key cards with a series of strings of data like 00000000555500000120000130000201100000120000014000002011. Previously, we would encode their room keys and then go on another machine to encode their parking system key. The machine that encode the parking keys in dead and the software is no longer supported.  BUT, the server that communicates with the gates and tells them that a key is valid is still working. I am not sure I wanna do anything with that.

Is there any program that I can use to listed to the gates like their server those which I can have look at the data being read which is basically 0s and room number 0s arrival date 0s departure and reply back asking them to open?

If not then I will even settle for a program that can tell if anything is written on a specific track and reply to open.

Any ideas would be use full!

Thanks