How to write to multiple modbus devices over TCP/IP simultaneously

I am looking for a way to connect to 2 devices, and send a command to both of them simultaneously. All of the software I have downloaded so far only allows one connection at a time.
The nice thing with modbus/TCP is, is that all devices can be both master, as well as slave (this is not possible with modbus RTU serial where there is 1 master and slaves).
I have done this many times with Pro-face GP4301TAD screens using 2 interfaces in the project (1 as modbus TCP master 1 as modbus TCP slave) and all together over the same ethernet interface.
Works fast and reliable.