I did some research on the networking and server- client stuff, and I found that clients need to be connected to server by specifying ip address and port. Now this creeps me out - I also found that to use port number it is supposed to be registered in some global database that contains all of them, so I can't just pick random one and go with it. What I want to do is make a multi player component for my game, that might even use dedicated server (in my case not a real server - just separate pc). Seeing that there are many many programs and games using one of the ports and those have its range since they use maximum of five numbers, do I really need to register the port to use it in my game?

While your server is listening on a specific port no other can do that and same thing around. If some other server process is already listening to a port you want to use you get an error saying something like "address already in use"

There is some kind of database available that can be querried for system defined ports and for what kind of service they are normaly used. But this is a different functionality.

This database is used to make applications idependent from fixed port numbers.

For professional development, there is no reason not to request a port from the IANA.

Professional or not, is it actually required to do this?

Professional or not, is it actually required to do this?

There is no enforced requirement. Nothing keeps you from setting up your game to run on port 80 even if it isn't using HTTP.

If you use ports that have well known uses, you may find yourself colliding with other applications or network traffic.

There is no enforced requirement. Nothing keeps you from setting up your game to run on port 80 even if it isn't using HTTP.