My IP Number for Windows and OS X. Requires Tap Tools and Jitter (tap.myip and jit.uldl can alternatively be replaced by Unix commands (use shell: http://www.publicbeta.cx/max/))
otudp for Windows. Abstraction using scripting to ensure compatibility with OS X.
Requires udp-write and udp-read which can be found at http://www.cnmat.berkeley.edu/max.
