NetServer::Generic hasn't been updated in 10 years, its author quit programming and became a famous science fiction writer.
in reply to Telnet server that read a single character
I would suggest using a more maintained and mature module like IO::Socket::Telnet::HalfDuplex.
For your error, the problem is that you're probably not connecting to a real terminal, I'm guessing you want the
telnet running on localhost.
Also, please tell us what you're trying to accomplish with single character read. It's not really what telnet is about, and perhaps you don't really want telnet either since it isn't at all secure.