Siemens SIMATIC S7-1200

Communication processor and Modbus TCP
13.8 Legacy Modbus TCP communication
S7-1200 Programmable controller
1264 System Manual, V4.2, 09/2016, A5E02486680-AK
13.8.4
Legacy Modbus TCP examples
13.8.4.1
Example: Legacy MB_SERVER Multiple TCP connections
You can have multiple Modbus TCP server connections. To accomplish this, MB_SERVER
must be independently executed for each connection. Each connection must use an
independent instance DB, connection ID, and IP port. The S7-1200 allows only one
connection per IP port.
For best performance, MB_SERVER should be executed every program cycle, for each
connection.
Network 1:
Connection #1 with independent IP_PORT, connection ID, and instance DB
Network 2:
Connection #2 with independent IP_PORT, connection ID, and instance DB