#34 Fail the Connect to HELMHOLZ NETLink PRO Compact gateway

[Marco Bartoli]

I have been using Snap7 for several years and with fairly recent SIEMENS S7300, S71500 PLCs connected, even directly, via ethernet cable, I have never had any problems.
I happened to have to communicate with an old S7300 CPU without an ethernet port. We therefore decided to use the NETLink PRO Compact gateway from HELMHOLZ, a SIEMENS accredited partner.
There was no way to connect to the PLC!
With the same test application, created with Delphi 11.1 Alexandria and which uses Snap7, we connected directly with the ethernet cable to another CPU of the same type but equipped with RJ-45 ports.
It works perfectly.

We found that the adapter exposes port 7777, while traditionally SIEMENS PLCs are contactable at 102.
We therefore instructed Snap7 to use port 7777 (verified that this was set).

p_u16_RemotePort = 2; // const in the Snap7.pas module.
var FPort : Word = 777;
FConnection.SetParam(p_u16_RemotePort, @FPort);

It doesn't work that way either!

The PLC logger reports the connection attempt rejected because the message is not correctly formatted.
We tried with port 2500 and, after setting in the PLC, the direct connection to the CPU works.
Snap7 therefore manages the Port correctly.

I ask for help.

If I don't solve it I am forced to use an OPC Client, which I would prefer to avoid.

Thanks