This is https://packages.debian.org/source/sid/netkit-telnet , with some bugfixes.
Note: Besides netkit-telnet, there's also a netkit-telnet-ssl package,
that only differs in the fact that the later adds an argument if you want to
make a telnet connection over SSL. The version on my fork (with the bugfixes)
for netkit-telnet-ssl also exists, and is updated quite more often.
- netkit-telnet-ssl: https://github.com/marado/netkit-telnet-ssl