strobe is a network/security tool that locates and
describes all listening tcp ports on a (remote) host or on
many hosts in a bandwidth utilisation maximising, and pro-
cess resource minimizing manner.
strobe is a tool for checking your services and make sure you know what is running.
Yes it can be used for poking for security holes on other hosts. If you use it for bad purposes, I'll be angry and universal karma will come after you :-)
It compiled relatively easily on NeXTStep (see the file strobe.c.ORIG for the original file, and strobe.c has the code I used to compile) using the stock cc from 3.3.