Q: How can I establish a serial connection (aka tip hardwire session) from one Sun machine to another?

A: Depending on which Sun machines you are connecting, you will need a certain type of null modem cable. Most Sun machines will require a DB25 male connector on the end.
SUMMARY:
1) Decide which machine will be doing the 'observing' and which will be the 'observed.'
2) Connect one end of the cable to serial port B on the 'observing' machine and the other end of the cable to serial port A on the 'observed' machine.
3) Establish a tip hardwire session.
4) How to send a break, terminate the connection, etc...


DETAILED:
1) Decide which machine will be doing the 'observing' and which will be the 'observed.'
For the purposes of this solution, the machine you will be working from will be called the 'observing' machine, and the machine that you are consoled into will be called the 'observed' machine. They keyboard should be disconnected from the 'observed' machine.

2) Connect one end of the cable to serial port B on the 'observing' machine and the other end of the cable to serial port A on the 'observed' machine.
Check the back of your machine for the serial ports labelled "A" and "B", connect the cable to the appropriate port on each computer. Some Sun machines have only one port marked "A/B" in this case, the single port acts as both "A" and "B". If you need the functionality of serial port "A", you just connect a regular null modem cable to it, however, if you need it to act as serial port "B", you will need a special Y-shaped adapter cable that 'splits' the port into "A" and "B".

3) Establish a tip hardwire session. On the 'observing' machine, type:

tip hardware

You will hear a beep and then see the following response:
connected

Unless diagnostic messages are scrolling up the screen, you will not see anything else. Hit ENTER a few times and depending on where you are, you will see either a command-line prompt or an "OK" prompt, signifying that the 'observed' machine is at the OBP level.

4) How to send a break, terminate the connection, etc...

HOW TO SEND BREAK:
If you need to send a break to the 'observed' machine, you cannot simply hit STOP+A. This is because the STOP+A will only have an effect on the machine you are sitting at. In order to send a STOP+A, or 'send break', signal to the 'observed' machine, you will need to use the following keystrokes:

~#

Sometimes it may not work the first time you do it, for one reason or another. Try it a few times. Keep in mind that you shouldn't be hitting the keys simultaneously, but you shouldn't be giving it a full second between keystrokes either.

HOW TO TERMINATE THE CONNECTION:
Ok, so you're connected to the machine, have done the work you needed to do on it and now you want to go back and work on your own machine. What do you do? To terminate the connection and return to a command prompt on your 'observing' machine, use this keystoke:

~.

Just like when you use the ~# keystroke, it may not work the first time around. When it does receive the signal, it will respond with:

~
[EOT]
and then kick you back to a command line prompt.

NOTE: You should only terminate a tip session in the manner described here. If you terminate it by killing the process, restarting the 'observing' machine or any other method, a file will be created which will prevent further tip hardwire sessions.