if postmaster is started on a certain port, should I be able to telnet there?

I started postmaster via:

./bin/postmaster -D data -p 7000 &

but why is a telnet localhost 7000

result in a refused connection even though

./bin/psql -p 7000 test postgres

works?

Connecting via DBD::Pg is failing and I wanted to try telnetting to
debug the problem but telnet results in refused connections.