Re: Serial/IP Socket Bridge - Project Suggestions

["PatrickLidstone" <patrickl@xxxxxxx>]

--- In ukha_d@y..., "Mark Marooth" <MMarooth@s...>
wrote:
> 
> 
> Chaps,
> 
> Today, whilst waiting for work compiles to run I started developing
a Serial
> Port to TCP/IP Socket bridge.  For me I plan to use this to
connect 
a collection
> of Weeder I/O cards to a serial port on an old 486 laptop which is
in turn
> connected to the house network.  This way I can telnet to the
laptop process and
> control/read the cards as if I was attached by serial port. 
Also, 
I can use the
> same facilities built into MrHouse to talk to these cards.
> 
> Laptop is totally stripped down and boots from the network so no 
hard disk,
> screen, keyboard etc.
> 
> One of the beauties of this development is that the software will 
handle
> multiple inbound connections (TCP/IP) to one or more serial 
connections.
> 
> I'm open to any functionality suggestions which would make this 
usable for other
> sorts of serial devices with the plan that I make the source 
available to the
> group for their use.

I've done something similar with the Homeseer plugins that I've 
written, and it has worked well. Here are some comments based on 
those experiences:

Suggestions:
1. Use broadcast rather than tcp/ip connections because multiple 
devices can then pick up status reports simultaneously without the 
need for multiple concurrent connections.

2. Reliability shouldn't be an issue on a home lan, and isn't 
relevant for frequently reported telemetry (e.g. temperature sensors) 
because it doesn't matter if a data report is dropped.

3. I wouldn't bother with using XML encoding on the wire, it's not 
well suited to parsing by embedded controllers. You can always 
generate XML locally from a byte packed string if you must.

4. If you byte pack binary objects (structs, numbers etc) be aware 
that you may have problems with portability across different OS's. 
ASCII strings have a lot going for them in this respect.

5. I think there's actually scope for formalising an HA standard for 
TCP/IP device control at the messaging level so that independent 
efforts will interoperate in the future.

> Initial development will be Linux based with a later backwards step
to windows.

Sockets programming on Windows has some major differences if using 
WinSock vs. GCC, and minor differences for GCC under Windows vs GCC 
under Linux.

HTH

Patrick



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