Getting Public IP without HTTP(S)

Hey /prog/,

Quick question. Would anyone know how to get the public IP of a PC without downloading it from a website?

Logging into the router via telnet or SNMP is also out the door as it needs to be something that would work on any machine without authentication.

Any services out there that offer this?

without downloading it from a website
Any services out there that offer this?

1. SSH to a remote machine and use netstat.

2. FTP, IRC, SMTP, etc. servers will often tell you the IP you're connecting from when logging in.