By looking through the files on the computer you discovered that apparently this CT card was some kind of telecommunication device.
There is a special protocol for it, called "CTIF".
You were wondering why someone invented all this when there are already standarised communication protocols.
You also found "Coincidence" which is a chat program which actually uses the CTIF protocol.
You can select a server and talk to other people who are also using the same server.
For some unknown reason the servers are selected by an ID which is just a number.
The "Coincidence" (and also the rest of the system) is using the latin alphabet. It's not what you use in everyday life but luckily you have already learnt it for programming.
Entering randomly chosen numbers as the server ID is not the best possible strategy because most numbers don't have Coincidence servers assigned.
There is an infinite number of numbers. Even when considering only the non-negative integers representable by a finite number of bits the number of available Coincidence server IDs is finite but still very large.
Luckily, on the computer you found some files listing various servers together with their assigned numbers.
Most of those were inactive. And those few which were active didn't have anyone to talk with.