The easiest way to do it would be through TCP/IP services.
With enough experience you can write your own server program, assign it to a port on the second RasPi, and configure the 'inetd' daemon to launch you program every time a request for that port comes in. That does take a fair amount of background knowledge though.
An easier way to do the same general thing is to run a webserver on the second RasPi and have the first one (with the GPS) make HTTP requests using the 'httplib' module (renamed to 'http.client' in Python 3). The general subject you want is "CGI scripting under Apache", and it's pretty simple once you know the basic tools.
'CGI' stands for 'Common Gateway Interface', and describes how the webserver passes information to the script that will process it. There's a set of standard variables the script can read, like REQUEST_URI and QUERY_STRING. Wikipedia has a decent description of it: http://en.wikipedia.org/wiki/Common_Gateway_Interface
'Apache' is the webserver on almost all Linux machines, and definitely the one you'll use on a RasPi. There's a good set of instructions on getting it running here: http://elinux.org/RPi_Apache2
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