Can concurrency, in a server, be implemented using only a single thread?

Question

I know multithreading is ideal for this situation, but would there be any instance of where this situation could be applicable?

Answer 1

Yes you could be serving multiple clients at once from a single thread. This is typically implemented using the select() or poll() socket functions.

A single threaded select() based polling server can use less system resources than a multi-threaded server.