Communicating across network 
Author Message
 Communicating across network

What is the best way to pass messages between FoxPro programs on different
machines on a (Novell) network?

I could, of course, insert a row into a table that is monitored by the
recipient machines but this is not practical. There would be one PC senting
the messages and about 8 recipients. All machines are operating unattended,
each recipient would only receive, on average, 100 messages per day (but
these would be clumped around 3 peak periods). Finally, the recipient
machines would have to react to the message within 1 second of it being
posted.

Thus, while it is possible for each to continually check for new rows in a
table, it would generate a lot of unnecessary network traffic.

I had considered using network broadcast messages but these don't queue
until read (problem during peak times).

DDE would be ideal. Does anybody know if it can be used across a network in
this manner (on a Novell network). If so, please provide some pointers.

I'm sure there's actually a very simple solution that I'm too thick to see
so feel welcome to have some fun at my expense :-)

TIA

anthony shipley

all opinions are just opinions



Sat, 24 Oct 1998 03:00:00 GMT  
 Communicating across network

Quote:

>What is the best way to pass messages between FoxPro programs on different
>machines on a (Novell) network?

------8<-------
>I had considered using network broadcast messages but these don't queue
>until read (problem during peak times).

------8<-------

Whilst playing with GPLIB I noticed it claims to be able to queue
messages at the server on netware and then pick them up at leisure.
It says it doesn't work under Win 95 so I can't test it.  You can get
GPLIB ant www.mhsoftware.com

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          |        W A R L O R D
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          |
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PGP Public Key Available

Key fingerprint =  DF 10 31 EF AA 7E 3A 61  32 2B 6E 56 71 44 14 20



Sat, 24 Oct 1998 03:00:00 GMT  
 Communicating across network


says...

Quote:

>What is the best way to pass messages between FoxPro programs on
different
>machines on a (Novell) network?

Is this a repost?  I seem to recall the same message last week.

Anyway 3rd party libraries such as netlib offer this capability.  You
could use the Novell SEND command w/i your programs.  There is a shareware
or free ware product that does this.

If you are using Window NT or 95 VFP can link into e-mail.

Talking of e-mail, why not use that alone for the time being?

Sal



Sat, 24 Oct 1998 03:00:00 GMT  
 Communicating across network

Quote:

> What is the best way to pass messages between FoxPro programs on different
> machines on a (Novell) network?
> I could, of course, insert a row into a table that is monitored by the
> recipient machines but this is not practical. There would be one PC senting
> the messages and about 8 recipients. All machines are operating unattended,
> each recipient would only receive, on average, 100 messages per day (but
> these would be clumped around 3 peak periods). Finally, the recipient
> machines would have to react to the message within 1 second of it being
> posted.
> Thus, while it is possible for each to continually check for new rows in a
> table, it would generate a lot of unnecessary network traffic.
> I had considered using network broadcast messages but these don't queue
> until read (problem during peak times).
> DDE would be ideal. Does anybody know if it can be used across a network in
> this manner (on a Novell network). If so, please provide some pointers.
> I'm sure there's actually a very simple solution that I'm too thick to see
> so feel welcome to have some fun at my expense :-)

There may be a simple answer, but I did not see it when I had to do the
same thing.  I looked at setting the refresh rate to 1 second, and I even
tried monitoring the direcory time stamp to see if an update occured.  
The problem was that any method that required the client machines to poll
continiously created high traffic.

The answer I used was to use a 3rd party library for peer-to-peer
communications.  When a 'client' workstation starts up it contacts the
master machine and registers with it.  When a change occurs the change is
sent to each one of the registered clients.  Traffic is low and  updates
updates appear instantly.  The system even sends out heartbeat updates
every 20 seconds.  If the master computer dies the clients know within 1
minute.

Warning - this approach is not for the faint of heart.  It took a while
to write and debug.  And at the time I used IPX as my protocol but
if redoing it would now go with IP.

Good luck.

Jack Linder



Mon, 26 Oct 1998 03:00:00 GMT  
 Communicating across network

Quote:

> What is the best way to pass messages between FoxPro programs on
> different machines on a (Novell) network?

May I suggest you take a look at our product NetLib?  Among its many
other features are functions to send and receive broadcasts.  For
example, to send a broadcast you use N_CAST().  To receive a broadcast
you use N_GETCAST().  To inform your program when a broadcast has arrived
so it can be handled gracefully use N_ONCAST().

You can get more information by visiting our home page at
http://www.netlib.com.

Thanks.

Neil



Tue, 27 Oct 1998 03:00:00 GMT  
 Communicating across network

Quote:

>The answer I used was to use a 3rd party library for peer-to-peer
>communications.  When a 'client' workstation starts up it contacts the
>master machine and registers with it.  When a change occurs the change is
>sent to each one of the registered clients.  Traffic is low and  updates
>updates appear instantly.  The system even sends out heartbeat updates
>every 20 seconds.  If the master computer dies the clients know within 1
>minute.

>Warning - this approach is not for the faint of heart.  It took a while
>to write and debug.  And at the time I used IPX as my protocol but
>if redoing it would now go with IP.

I am interested in having a look to this library.  Is there a demo/shareware
available?  Where can I get it?  Or at least documentation about it?

Thanks!


 Life: (n) Terminal disease, {*filter*}ly-transmitted.



Thu, 29 Oct 1998 03:00:00 GMT  
 Communicating across network


Quote:

>What is the best way to pass messages between FoxPro programs on different
>machines on a (Novell) network?

<snip>

There are two methods we use for network communications.  The first, and oldest
method is to use an ASCII FIFO file for sending messages to a machine. There are
two files for each client (request/response).  We created a library that takes
care of all of the file handling since FoxPro updates at once per second at
best.

This method does cause a lot of network traffic and we've never tried it with
more than 2 clients.  Also the polling of the FIFO files are performed by the
clients several times a second.

The second method is using NetLib by Pinnicle which allows for IPX
communications.  Using the built in functions of this library we set a trap for
IPX packets and when received, the process is halted and we call a IPX message
handler.  Then the process is resumed and the new data is used when required.  
The problem is that Windows 95 seems to intercept the IPX packets so we can't
use Windows 95 with this solution (yet).  The idea of a heartbeat packet every
so often is something we've played with but our solution did not require it
since we used two-way communications with an ACK protocol instead.

I strongly suggest you stay away from a FoxPro coded solution if you are trying
to make a 1 second or faster update rate.

Jon



Tue, 03 Nov 1998 03:00:00 GMT  
 Communicating across network

<snip-dragon was here>

Quote:
>I strongly suggest you stay away from a FoxPro coded solution if you are trying
>to make a 1 second or faster update rate.

Sigh. We actually have only about 1000 transactions per day so I think
we'll start by reopening the table every time (1 second is not toooo bad).
If that isn't good enough we'll try the messaging route.

Thanks to all respondees.

anthony shipley

born again init string (originally known as init string from hell)



Fri, 06 Nov 1998 03:00:00 GMT  
 
 [ 8 post ] 

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