Please do not start 2 threads of the same topic. I did answer your original question at: https://forum.prosysopc.com/forum/opc-ua-simulation-server/prosys-opc-ua-simulation-server-and-prosys-opc-ua-client/#p4792. But the short reference is that it is completely outside the scope of OPC UA in that sense that it is basic networking i.e. the the opc.tcp connections run on a normal TCP connection thus the same ruleset apply, i.e. the speciifcation basically says just https://reference.opcfoundation.org/v104/Core/docs/Part6/7.2/
“TCP/IP is a ubiquitous protocol that provides full-duplex communication between two applications. A socket is the TransportConnection in the TCP/IP implementation of the OPC UA Connection Protocol.

The URL scheme for endpoints using OPC UA TCP is ‘opc.tcp’.”

They can be in different networks, but you will need to have a network path from the client to the server. Typically this means that the client must be able to access the other machine via some IP or hostname or URL, and in almost all network setups the server’s side will have a firewall at some point which will need to allow the traffic to the port the server is listening, i.e. “open port” in the firewall.

It should be noted that opc.tcp is just only one connection protocol that OPC UA has, but basically that is the one everything uses, so I’ll ignore other forms in this answer.