CoolTalk does not actually require any type of Server to operate.
All data is passed from user to user directly.
The 411 server provides an easy way to locate other users. This is especially important for dialup users whose service providers use dynamic IP addressing. In this scheme, your IP will be different each time you connect to the network, and thus nobody will know your address ahead of time. Each time you run CoolTalk, it sends your IP and other information to whatever 411 server you have specified. The server then makes a note of their presence.