IRC is what introduced me to client-server architecture. Like many back then and still today I had this vague idea of "server" meaning some kind of powerful computer with no monitor. I used to love IRC but I was only in dialup Internet and wasn't allowed to use it very often. I sorely wanted to be able to idle on IRC at all times like some people did. But then I discovered I could actually install unrealircd on my own computer! I had my own little network with eggies talking to each other. I experimented with different clients and even connecting manually with telnet. It was great!