In the early 2000s I had a program on my girlfriend's, now ex-wife's, family computer that would kill the AOL process when sent a specific string over a TCP por

In the early 2000s I had a program on my girlfriend's, now ex-wife's, family computer that would kill the AOL process when sent a specific string over a TCP port so that I could call her when her sister was using the computer. That combined with a DynDNS client let me call anytime. Her sister caught on but couldn't prove it.