hp-tools is meant to be a set of tools built on top of ucspi-tcp or s6-networking or similar, for creation of simple honeypots.
I started this pet project with utility hp-smtpd that pretends behaviour of qmail-smtpd and logs every incomming byte to the standard error output.
It could be executed with command:
tcpserver 0 25 ./hp-smtpd
where tcpserver is from ucspi-tcp package.
To compile it run:
make