Multi-threaded Modbus TCP Server: Issue with modbus_set_socket() and Context Handling

[Pcdwarf]

Hello,

I’ve implemented a Modbus TCP server that accepts multiple concurrent client connections. For each new connection, the server spawns a new thread to handle the specific client’s requests.

Initially, I assumed that the listening socket was handled by a single Modbus context, and each client would be managed as an independent connection within this context.

Here’s what I did:

I passed the same Modbus context and unique clientSocket to each thread.
I used modbus_set_socket() within each thread, expecting that it would handle individual client connections independently.

Issue: It appears that modbus_set_socket() modifies a single property in the shared Modbus context rather than managing it on a per-thread basis. Consequently, when multiple threads attempt to set the socket within the same context, the behavior becomes inconsistent and connections get mixed up.

Questions:

Would it be viable to create a shallow copy of the Modbus context for each connection and then use modbus_set_socket() on each copy?
Is there a recommended approach to implementing multi-threaded handling of client connections, or is multi-threading considered problematic in libmodbus?

Any advice on best practices for this situation would be highly appreciated.