Liblo is a lightweight library that provides an easy to use implementation of the OSC protocol (see http://www.cnmat.berkeley.edu/OpenSoundControl/ for details).
Liblo is portable to most UNIX systems (including OSX) and Windows. It is released under the GNU General Public Licence.
NOTICE FOR MAC OS X:
Mac OS X defaults to ipv6 but most of the currently available OSC applications
like Pd and SuperCollider doesn't listen on ipv6 sockets. for now it's safer to
turn off ipv6 support in liblo (using ./configure --disable-ipv6).