Allow port number to be specified with tcp hostname

[djholt]

This is minor but useful when a different port number needs to be specified (when tunneling over SSH, for example).

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 60.72%. Comparing base (584a14f) to head (5cc9627). Report is 19 commits behind head on master.

Files with missing lines	Patch %	Lines
meshtastic/__main__.py	75.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #673 +/- ## ========================================== + Coverage 60.70% 60.72% +0.02% ========================================== Files 24 24 Lines 3667 3672 +5 ========================================== + Hits 2226 2230 +4 - Misses 1441 1442 +1 ``` | [Flag](https://app.codecov.io/gh/meshtastic/python/pull/673/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=meshtastic) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/meshtastic/python/pull/673/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=meshtastic) | `60.72% <80.00%> (+0.02%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=meshtastic#carryforward-flags-in-the-pull-request-comment) to find out more.

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[ianmcorvidae]

Looks like the test failure is unrelated, to do with test fuzzing for some other stuff. This looks good, thanks!