Date: Fri, 03 Apr 1998 17:32:44 +1200 From: physmsa AT cantua DOT canterbury DOT ac DOT nz (Mr M S Aitchison) Subject: Re: Port Forwarding To: opendos AT delorie DOT com Message-id: <199804030532.RAA00244@cantua.canterbury.ac.nz> Precedence: bulk I wrote a program many years ago which forwarded everything coming in a serial port to another port (could have been serial or parallel - I used parallel). This was one-way, simple handshaking that worked, and the TSR sat in memory of a286 at first, then a 486, that didn't bother other programs running. This was to share a printer, and it was very good at that, so a few years later I tried another version to share a modem. This "sort of" worked up to about 19.2k baud on a fast computer, but wasn't nearly successful - it needed more work to handle all teh modem lines (and ring indicateor will still be a problem), chewed up lots of cpu, and really needed a 16550 (as it was, on a 16450 it really needed the computer to be dedicated to the job to handle 19.2k, and 38.4k lost a few characters). Plus it gobbled up IRQ's (3,4 and mouse was 5). Al the problems people suggested, and we sort of decided sharing serial ports over a network was a much better idea. Unfortunately PNW doesn't do this (unless it is for a unidirectional printer), but other PC software can. In the case of a modem I'd have to ask if this modem sharing is for an internet connection (in which running proxy/gateway software on the PC with the modem is a very good idea). If you can be sure only one computer at a time will use the modem, and it is an external modem, a simple switch on the serial leads might do. We even ran a system here with diodes and pull-up resistors so several computers could send and receive without having to change a switch (just needed there to be no way two computers would send at the same time). I can post the circuit is needed. --------------------------------------------------------------------------- Mark Aitchison, \_ Phone: +64 3 364-2947 home 337-1225 Dept of Physics & Astronomy,