Write registers in parallel over tcp

[pdorrestijn]

Thank you for this library.
I was told when you communicate modbus over tcp, it is possible to send multiple messages using the same connection and write the holding registers in parallel.
Each request would be differentiated with an id.
However the TCP transaction handler in this library has a mutex in the send method preventing parallel messaging.
Ofcourse I could create multiple connections, but I am wondering: is there a way to circumvent this mutex?

[wwhai]

you need lock this connection