Telnet and Control break Key

Dar Scott dsc at swcp.com
Tue Sep 3 00:10:00 CDT 2002


On Monday, September 2, 2002, at 08:58 PM, Luis Camou wrote:

> I agree with you. I am sorry  I did not phrase my questions right, 
> I have
> the serial part working ... thanks to Sarah ( Serial test ) , what 
> I need is
> the break key ( windows?) for the serial part to do the password 
> recovery
> :-).

Hmm.  "Break" may be ambiguous here.

If you have been using a telnet client to talk out the serial port, 
you probably need the telnet break--byte code 129, I think.

However, if you need an RS-232 break, that is something different.  
It is not a byte, but an action out-of-band.  A serial line is 
either in the mark (1) or space (0) state.  The serial line is 
normally held in a marking state (1).   When a character is sent, a 
space (0) start bit is sent, then the data bits and then one or two 
mark (1) stop bits.  A break is a space that is held longer than a 
character time, that is, past the expected mark stop bit.

I don't know of a direct way to send this kind of break with 
Revolution.  However, here is an idea that might work.  Close the 
serial connection, open it again at a much lower bit rate, send a 
null, delay the break time, close the connection and reopen it at 
the original rate.

(The handshake lines might drop; this probably won't be a problem, 
but it might be.  You might need to change the serial cable wiring 
slightly.)

I think your problem is tougher if this is what you need.  I'd like 
to see how you do this if this is indeed your problem.

Dar Scott




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