Here is manual.
https://cache.industry.siemens.com/...95681/v1/s71200_system_manual_en-US_en-US.pdf
You need to look page 1186 (Note that this is older manual, as it explains little bit more than newer manual)
There is Note onn page 1182 (Which is also on newer manual):
Multiple server connections
(1200, not sure about 1500CPU)
-Each MB_SERVER connection must use a unique instance DB.
-
Each MB_SERVER connection must assign a unique IP port number.
- Only 1 connection per port is supported.
- Each MB_SERVER connection must assign a unique connection ID.
- The MB_SERVER must be called individually for each connection (with its respective instance DB)
.
On example on page 1186 and how I understand this, you need different TCP ports for every communication on PLC as Server.
Max number for multiple coms on 1200 was 4 or 8 depending of FW?
I don't use S7 but if its Modbus TCP you should be able to have multiple masters, unless the S7 has some weirdness to stop that happening.
Hopefully rQx can change modbus 502 port on PC side for 503 or something else, as changing port is not option on all softwares.
(And if you can't, then you need reprogram 502 port to different on switch or different routing program between your scada and PLC.)
But it is Siemens, nothing new
All coms should use 502 port as Schneider / Modicon PLC do without need of different ports for every communication.
p.s It is maybe possible that you use one DB and port 502, but then have multiple communications same time to this DB / port 502.
But manual says it differently on this
"Only 1 connection per port is supported."