Closing connection on any error

[alexjoedt]

This pull request updates the error handling logic in the tcpclient.go file for the Modbus TCP client. The main change is to simplify and strengthen the handling of write errors when sending data over the TCP connection: now, the connection is closed on any write error, not just specific ones like EPIPE. This ensures the client always recovers cleanly from any corrupted or lost connection state.

Improved error handling for TCP writes:

• The Send method now closes the TCP connection on any write error, not just EPIPE, to ensure the client recovers from all possible connection issues and avoids protocol desynchronization. This change also improves the clarity of comments explaining why this is necessary for a request/response protocol like Modbus.

Code cleanup:

• The unused import of the errors package was removed from tcpclient.go.

Resolves #97

[andig]

Closing on every error is what evcc has been successfully doing for a long time.