Add setting of sin_len/sin6_len for BSD and macOS

[softins]

Short description of changes

This is a test to see if it fixes the problem reported in #3758

CHANGELOG: Client/Server: Fix a potential problem with sockets on BSD/macOS

Context: Fixes an issue?

Hoping it might fix #3758, but don't know for sure

Does this change need documentation? What needs to be documented and how?

No

Status of this Pull Request

Ready to test. It compiles, but don't know if it fixes the issue.

What is missing until this pull request can be merged?

Testing

Checklist

• I've verified that this Pull Request follows the general code principles
• I tested my code and it does what I want
• My code follows the style guide
• I waited some time after this Pull Request was opened and all GitHub checks completed without errors.
• I've filled all the content above

[ann0see]

Unfotunately, it still hangs. It seems to take some more time before it hangs. But this might also be to less people being active on the servers at this time. I still think this is a good bug fix.

[ann0see]

I'm inclined to approve it as is - even though it doesn't fix the bug.

[pljones]

Needs a better change log message -- it looks like it's initialising the BSD IP protocol packet (??) length in the header (not present on other *nix flavours). If that was missing, I'm surprised it wasn't core dumping like mad - unless it really works like other *nix flavours underneath.

But yes, looks like a good fix to have, if it means the header is thus compliant.