BBS: Inland Empire Archive
Date: 07-19-92 (15:08) Number: 92
From: RICK PEDLEY Refer#: NONE
To: MIKE TRINASTICH Recvd: NO
Subj: Network Considerations Conf: (2) Quik_Bas
On 07-16-92 Mike Trinastich wrote to All...
MT> Can anyone offer any information on developing programs that will
MT> run
MT> safely on both a network and non-network system without writing 2
MT> different versions? We haven't experienced any problems so we tell
MT> our
MT> customers that our programs run safely on a network. Like any
MT> programmer,
MT> the more you program the more sophisticated your programs get and
MT> network
MT> compatibility is starting to worry me, especially since I have no
MT> network
MT> experience. Until we take the time to network our machines at work
MT> can
MT> anyone offer some tips?
I recently added code to a program so that a single byte switch
determines whether it runs as a stand-alone or network version.
A couple of things I had to contend with that I hadn't thought too
much about until I tried to make a program network-compatible:
1. File access menus have to allow for drives lettered as high as Z:,
not just up to F: or G: as you might expect on a stand-alone
system.
2. A network administrator might have organized things so that all
user data files are stored on a separate drive, or even
on a different server, so if your program is hard-coded to create
user directories just below the program directory on the same
drive, you'll need to make it more flexible.
3. If you expect several users to use the program at once, you'll
probably need a menu so a user can select his own data directory,
and keep a separate program configuration file here for each
user. For example, one user might want to run in 50-line mode,
no mouse, a personalized color scheme, local Epson FX-85 printer;
another user might have an entirely different setup. If a single
configuration file were kept in the program directory -- well, you
can see the problem this would cause.
3. The remote printer might appear as LPT2: to a terminal, so your
program needs to be able to direct output to LPT2: (this is
something I'm currently having trouble with).
4. Network drivers can eat up an extra 30 - 70K of base memory on
a terminal, so your program has to still be able to function in
reduced RAM.
5. If you're converting a stand-alone program, probably you'll have
the terminal load a copy of your program locally and send data
files back and forth to the server. Things can really slow down
if your program has overlays or chains a lot, but it works well
for one-piece programs and small data files.
6. If several users can have access to a file simultaneously, then
you have to build in code that restricts simultaneous access. If
SHARE.EXE is loaded then you can use BASIC commands to LOCK
records for read/write etc., but many programmers prefer to use
`hard' record-locking, where a one or two byte field in each
record is reserved for a locked/unlocked flag.
7. You need to be able to tell if SHARE is loaded, and possibly
which network program, usually Lantastic, Novell Netware,
or Banyan Vines.
This should get you started. The hardest thing I found was having to
adjust my thinking, having gotten locked into a single machine -
single user way of looking at everything. BTW, I recently bought a
book called PC Connectivity by John Dvorak that comes with 3 floppies,
one of which has Lantastic Z on it. Lantastic Z allows you to connect
two computers by null modem or parallel cable and run a network between
them, either server-terminal or both machines can be servers =and=
terminals. The book was $60 Cdn (ouch, but there's lots of other
stuff in it), and about $50 for a 50' null modem cable. I also got
a couple of serial switch boxes because I don't have a 3rd COM port.
If the machines are close to each other, an 8' parallel cable and
a couple of parallel cards is much better (and faster) and will cost
about $50 US. It's a great way for programmers to test out their
code without having to find some place that'll let you experiment on
their network. As a side benefit, it also frees up tons of drive
space if you've been keeping copies of big applications on both drives
(depending on the license specs for each program, of course ;-) ).
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