What is the serial port on the T5140 used for.
To check on console logs, troubleshoot h/w issues and configure netmgt port etc..
BigAdmin: System Administrator Resources for Sun Servers With CoolThreads Technology (T5140/T5240 Servers)
I am referring to the serial port not the ser mgt port
I myself or i have not seen anyone to use that.
A DB-9 TTYA serial port is provided for serial devices
You may want to look into the product notes/documentation
It's up to you. You can plug a VT100 if you can borrow one from a museum, a modem if you want to experiment with PPP, whatever.