http://support.microsoft.com/kb/231866

so IAC GA would be 0xFF 0xF9.

My googling also turned up that some mu*s use IAC EOR, which according to some site would be 0x19.

Now a PROPER telnet implementation should probably negotiate the use of GA but... uh...

Edit: so wouldn't implementing IAC GA/IAC EOR be as simple as dumping those bytes in the bitstream? Anything not conforming to telnet protocol would display "ÿù" or "ÿ↓", though.