[geeks] stupid question: software null modem?

[der Mouse]

> [...] is it impossible to use a regular serial cable to do the work
> that you would normally use a null modem cable for, by way of some
> software?

Basically, yes, it is impossible.

In theory it might not be; it is conceivable that someone, somewhere,
has built a serial port that's capable of switching which pin gets the
driver and which the receiver.  But it's a hardware issue; most (all,
to a first and probably even second or third approximation) serial
port hardware simply is not capable of doing other than sending on pin
A and receiving on pin B (exactly what A and B are depends on the
connector used and sometimes other things - eg, for DB25, whether it's
wired as DTE or DCE).  If your hardware can't do it, all the software
in the world won't help.

> (I'm having trouble scrounging a null modem cable up from around the
> house, and I can't get out until tomorrow, if that, to go buy one.)

No soldering iron around?  Or even twist-on connectors?  It's not that
hard to strip the outer insulation from a cable, find the wires
carrying data, and cut them and reconnect them swapped.  In some
circumstances I'd even twist the wires by hand and just make sure
they're not near anything conductive, if twist-ons or alligator clips
or etc aren't at hand.

Actually, it occurs to me that it depends on what you want.  The above
is assuming it's swapping the data transmit and receive pins that you
care about.  If you're talking about things like DCD and RTS, with the
data pins fine, then it's much more likely that suitable software can
help, by arranging to ignore the lack of certain signals.

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