Testing firewall chains

[Philip Lehman <lehman@gmx.net>]

I have set up firewalling on a gateway which connects my LAN to
the net (using ipchains with a 2.2.14 kernel). How could I test my
firewall chains from outside? Are there public services out there
which would do a port scan on my server, for example?

I'm pretty new to advanced networking and after reading the HOWTOs and
the ipchains docs I think I understand how it works, but I still feel
a bit insecure. Any pointers to more documentation are welcome too.

-- 
Philip Lehman <lehman@gmx.net>