Flag: hoist_the_anchor_we_leave_the_port
The challenge flavortext says "Do you know nmap?".
Running nmap against the CTF host produces:
$ nmap zeromutarts.de
Starting Nmap 5.00 ( http://nmap.org ) at 2013-11-15 21:43 EST
Interesting ports on zeromutarts.ikmfbs.ing.tu-bs.de (134.169.18.173):
Not shown: 992 filtered ports
PORT STATE SERVICE
7/tcp open echo
22/tcp open ssh
80/tcp open http
2222/tcp closed unknown
3333/tcp closed dec-notes
8000/tcp open http-alt
8080/tcp open http-proxy
8085/tcp closed unknown
Nmap done: 1 IP address (1 host up) scanned in 10.62 seconds
The echo service running on port 7 is unusual; what happens if we connect to
that port?
$ nc zeromutarts.de 7
flag{hoist_the_anchor_we_leave_the_port}
The flag is thus hoist_the_anchor_we_leave_the_port.