The newline character will print in your output, and your output will look less nice. Part of the point of this assignment is to force you to meet a specification strictly, even though the spec has some onerous details. People in industry mentioned that our students don't get a lot of experience in terms of dealing with the need for well-defined interfaces, so I put a little bit into this assignment. Maybe we should test your MP's in pairs, with client and server from different people. We would have to tweak the ports, I guess.
Carriage return is displayed.
If you call strlen on what you get from fgets, it will count the carriage return. Don't special-case it.