Add option to not close tcp on passive mode timeout

[arrangabriel]

Description

In my usage of your library I would like to continue sending requests to a server, even if one times out. Therefore I have added an option to the Modbux.Tcp.Client module that allows users to control whether the TCP connection should be closed when a timeout occurs in passive mode. The option close_on_timeout is set to true by default, so as to be backwards compatible.

Timeout handling logic:

• Modified the timeout error handling in :confirmation so that the socket is only closed on timeout if close_on_timeout is set to true.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update (the new option has been added to the documentation for the tcp client module)

How Has This Been Tested?

The change is very minor, albeit hard to test well. I have not added any tests for it.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

---

Note

Adds close_on_timeout option (default true) to control whether the TCP socket is closed on passive-mode timeouts and updates timeout handling accordingly.

• Modbus TCP Client (lib/tcp/client.ex)
  • Option: Introduces close_on_timeout (default true) in Client struct and init args to control socket closure on passive-mode timeouts.
  • Behavior: In :confirmation, only closes socket on :timeout when close_on_timeout is true; otherwise keeps connection open and resets cmd/msg state.
  • Docs: Updates module docs to document the new close_on_timeout option.

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