That brings up a very important point:   many server programs need to handle “many, even hundreds, of input channels,” but a simple socket-select design often works beautifully for them, with no need for threads.

Also, if the design does start getting complicated, a little bell should go off in your head:   “this has probably been done a thousand times before, and it's got to be on CPAN somewhere.”   So, before you go far down the primrose-path of coding something new, you stop writing and start looking.   Works every time.   You can find everything from well-tested component pieces, to battle-hardened complete frameworks.