SERNET |
Dilwyn Jones
SERNET was developed from Phil Borman's MidiNet software. Bernd Reinhardt modified the software to use the serial ports instead of the MIDI ports. An article describing the original SERNET appeared in QL Today Volume 1 Issue 2, page 36.
Several people have reported problems getting SERNET to work. I was one of those initially until I upgraded to a newer version and found the correct wiring for the machines concerned.
So far I have not yet made up a cable to connect a standard QL to anything, but since PCs and Auroras are likely to use similar serial ports, the following cable diagram should help you get simple 2 machine setups to work.
Cable wiring is pretty critical. For two machine setups, you need to cross connect DSR and DTR, CTS and RTS, TxD and RxD between the serial ports, and also connect up the Ground pins on both machines, a total of 7 connections. The diagram in Fig. 1 shows how to connect up serial ports which use the 9 and 25 pin D type connectors, wired up as PC style serial ports. Buying a 'Null Modem' cable should work for systems with PC style serial ports. Some serial Interlink or Laplink cables may also be suitably wired for use with SERNET.
SERNET requires SMSQ/E to work, since standard QDOS cannot handle the independent input and output serial channels (SRX1 or SRX2 for receive on serial ports 1 or 2 and STX1 or STX2 for transmit on serial ports 1 or 2).
| DB9 | DB25 | SIGNALS | DB25 | DB9 |
| 2 | 3 | RxD-TxD | 2 | 3 |
| 3 | 2 | TxD-RxD | 3 | 2 |
| 4 | 20 | DTR-DSR | 6 | 6 |
| 5 | 7 | GND-GND | 7 | 5 |
| 6 | 6 | DSR-DTR | 20 | 4 |
| 7 | 4 | RTS-CTS | 5 | 8 |
| 8 | 5 | CTS-RTS | 4 | 7 |
| Figure 1 - Cable diagram for standard 2 computer setup | ||||
It is absolutely vital that cabling is correct. It is unfortunately possible to get it to seem to work when you get the handshaking wrong, but a typical sympton would be that communication would work with very low baud rates or short transmissions, but errors would creep in during longer transfers.
To make a cable to connect three or more machines, you have to wire up a special cable where output signals from one machine are wired to the input of the next and so on, to form a complete circle or ring from first to last computer.
Now that you have made up a cable, you need to configure the SERNET code file supplied with SMSQ/E. Look for a file called SERNET_REXT (or sometimes SERNET_RXT) and then use MenuConfig level 2 to set it up to your requirements.
Make sure that you avoid v2.24 of SERNET, this had some problems which meant I wasted a lot of time trying to get it to work without knowing it wouldn't work at all. When I was sent v2.25, the problems went away and I was able to happily SERNET using that version.
MenuConfig offers two configuration items - select the SERNET v2.xx option first. This will ask you to make a few entries:
Name for Serial Receive - enter SRX1hd or SRX2hd
Name for Serial Transmit - enter STX1hd or STX2hd
Server timeout - enter 0 here unless you know better! (1 or 2 can be used with slow computers, although these settings affect performance.
If your hardware does not support hardware handshaking, you can replace the 'hd' parameters with 'xd' for xon/off software handshaking instead. Hardware handshaking is preferable if supported.
The other configuration item allows you to specify SERNET/Modem. This asks if you want sernet to work via modem. Select the NO option for our cable connection. Now select 'OK' to save the reconfigured file.
Before you load SERNET, set the baud rates for both computers. 9,600 baud is a good value to start with, although this will prove to be slow. When you get it working, experiment with higher baud rates, whatever your hardware is capable of.
Install SERNET_REXT with the LRESPR command
LRESPR FLP1_SERNET_REXT
or whatever. Activate the sernet job with the command SERNET.
The sernet station numbers (similar to QL network station number) is set with the command SNET. To set your computer to be station 1, use
SNET 1.
To set it to be station 2, use
SNET 2
and so on. They seem to default to station number 1 - both machines on a 2 machine system can both be left as station number 1.
You are now ready to test the connection. From BASIC, try a command such as
DIR s1_FLP1_
If you get the list of files, all is well. Try copying or spooling a file over the network to the screen of the other computer:
COPY FLP1_FILENAME TO s1_SCR
The sernet device name defaults to S, so station 1 is device S1_ and station 2 is S2_ This can be changed -to change the sernet device name to R for example:
SNET_USE R
If another program closes the serial ports used by sernet for some reason, you can reopen them with the SNET_ROPEN command.