Can anyone help me with a problem facing at my site location?

I have a program which access IRC module along with CPU Ethernet port to generate Redundant communication setup for 2 different IP.

We have configured MB_SERVER_DB instances in Rung 16 and Rung 19

IP A: 192.168.1.23 (CPU)

IP B: 192.168.2.23 (IRC Module)

However, below happens.

1. If Line A is connected then line B is disconnected.
2. If Line A is disconnected then only Line B becomes Active.
3. After Step 2, Line A also stops communicating.

Can anyone help me in resolving this issue. i am currently stuck at site.

My guess is the MB_Server is only capable of connecting to 1 client simultaneous. Try a second instance of mb_server at another port for the redundant connection.

edit: sry, didn't read you post correctly and didn't chk the attachment. You do have 2 instances at separate ports?

Hi Enof,

Yes i do have 1215C with IP 192.168.1.23 and IRC module with 192.168.2.23

A manual page reads that multiple DB instances can be used. but i have used it but still its not able to communicate simultaneously on these two IP address. 

Do you use a separate port for each mb_server instr, e.g. 502 rsp 503?

unknown user

Multiple server connections
Multiple server connections may be created. A single PLC can establish concurrent
connections to multiple Modbus TCP clients.
A Modbus TCP server can support concurrent connections up to the maximum number of
Open User Communications connections allowed by the PLC. The total number of
connections for a PLC, including Modbus TCP Clients and Servers, must not exceed the
maximum number of supported Open User Communications connections (Page 801). The
Modbus TCP connections may be shared between Client and Server type connections.
Individual concurrent server connection must follow these rules:
● 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).

I have used MB_SERVER_DB as DB1 for both rung 16 and 19.

But since these two are in different IP ports hence i could use Port 502 for both the TCON's

please read:

Each MB_SERVER connection must use a unique instance DB.

and:

Each MB_SERVER connection must assign a unique IP port number. Only 1 connection
per port is supported.

Otherwise you get the behaviour you described.

Also make sure you define another connectiopn id!

good luck!

If i make as below by creating two difference MB_SERVER system blocks.

192.168.1.23 as MB_SERVER_DB to access data from 192.168.1.101

192.168.2.23 as MB_SERVER_DB_1 to access data from 192.168.2.101

and will this work? need your expertise on this.

Hi enof,

The problem was solved. All i had to create is two DB instances as below.

DB1 = MB_SERVER_DB

Connection ID=2

Local port = 502

DB7 =  MB_SERVER_DB

Connection ID=3

Local Port=502

By this i would able to transmit data simulataneously on:

S7-1212 CPU on its Ethernet port 192.168.1.23

IRC module on its ethernet port 192.168.2.23

Thanks for your suggestions.