Re: RPGLE Socket Communication with Modbus

Boy that is old isn't it. Not many protocols of that type from 1979 are still in active use.

Undoubtedly it can be programmed in RPG but given that there are freely available Java, Python, and PHP libraries out there it might make more sense to stick one of those on the end of a data queue and communicate that way.

Clearly though, as Buck has pointed out, there's not a shortage of basic documentation on the protocol.


Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Jul 12, 2019, at 11:17 AM, Buck Calabro <kc2hiz@xxxxxxxxx> wrote:

On 7/10/2019 3:54 PM, Russell Wesh wrote:

I am hoping to get some assistance to communicate in RPGLE with a pick to light device that uses Modbus protocol

My personal experience with low level communications is that there are
two learning curves that need to be climbed:
1) How does the protocol work?
2) How to make RPG implement the protocol?

I myself have not had any experience starting with (2) before finishing
(1). If you have experience with other communications, set up a working
environment with the vendor's application and sniff the communications.
Wireshark is one such sniffer.

Modbus is an old protocol. The canonical reference is at
http://modbus.org/ In particular look under Technical Recources and try
the TCP Toolkit. That should get a 'known working' bit of code running
with your device. This will enable you to sniff out what a working
exchange looks like.

--
--buck

http://wiki.midrange.com
Your updates make it better!

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