Hi,

3.1 – On MODBUS TCP server

3.2 – On MODBUS TCP client:

Use MB_CLIENT instruction on the client:

Each connection need a block call (with different instance DB). ID and port must match with the server).

4- Status 7002 = meaning that there is no client connected.

NOTE: As from CPU FW4.0 / STEP 7 V13 SP1, the blocks MB_CLIENT / MB_SERVER was changed.

Now they are similar to S7-1500. The main difference is that now the connection definition is not made in block inputs but else in a external place (DB).

To create the connection reference DB, create a DB as usual, and as variable (any name) you should type (manually) as data type “TCON_IP_V4”.
The blocks online help shows the meaning of the variables.

I attached now two examples at one zip file: one for FW>4, other for FW<=3 (as original)

In the post of 28/04/2018 I place a V15 project version + cast showing the project steps.