When was your libcod compiled? (post first few lines of the startup log)
Because it is possible it wasn't supported then yet. (ip support for 1.0 was added around 2 months ago)
libcod versions are available here:
Build with https://github.com/M-itch/libcod
http://znation.nl/libcod/
Build with https://github.com/kungfooman/libcod
http://dbg.killtube.org/libcod/libs/
http://killtube.org/downloads/libcod/