I have Freezing problem at Telvent HU-AF.

You say about the first image that server1 is working here, but I don't see any Modbus telegrams. To me this indicates that server1 is not polling the RTU here, but only a TCP handshake is sent back and forth to keep the link alive.

Can you explain the details about the timing and order of your actions in relation to the screenshots? What exactly was going on each time you captured these images? Were both servers running, or only server1 or server2? Could you see valid values in your Citect client? Does the Citect Kernel on both I/O servers show any problems/details for your I/O devices or drivers?

Also, the fourth image shows that server2 stops polling (no more Modbus traffic from a certain point) and 10 seconds later the RTU closes the TCP channel. To me that indicates normal time-out behaviour from the RTU side.
The question is why server2 stops polling. Is that because something you did? If at that point, for example, server1 comes online and takes over the communication, this is exactly what you want to happen, I would think.

You say about the first image that server1 is working here, but I don't see any Modbus telegrams. To me this indicates that server1 is not polling the RTU here, but only a TCP handshake is sent back and forth to keep the link alive.

Can you explain the details about the timing and order of your actions in relation to the screenshots? What exactly was going on each time you captured these images? Were both servers running, or only server1 or server2? Could you see valid values in your Citect client? Does the Citect Kernel on both I/O servers show any problems/details for your I/O devices or drivers?

Also, the fourth image shows that server2 stops polling (no more Modbus traffic from a certain point) and 10 seconds later the RTU closes the TCP channel. To me that indicates normal time-out behaviour from the RTU side.
The question is why server2 stops polling. Is that because something you did? If at that point, for example, server1 comes online and takes over the communication, this is exactly what you want to happen, I would think.