I want a script to start and interact with a long running process. The process is started first time the script is executed, after that the script can be executed repeatedly, but will detect that the process is already running. The script should be able to interact with the process. I would like this to work on Unix and Windows.

I am unsure how I do this. Specifically how do I detect if the process is already running and open a pipe to it? Should I use sockets (e.g. registering the server process on a known port and then check if it responds) or should I use "named pipes"? Or is there some easier way?