modify ptyio to send keepalive packets

Hi
Is there anyway to modify the pty programs to somehow do keepalive,  
as our inactive telnet sessions over a VPN disconnect
after an hour of inactivity.   I see a select in the ptyio.c code,  
but it specifies 0(zero) as the timeout value.  don't
know if that is the place to do it tho'.

Ed