bug#45821: 28.0.50; Add UDP support for Emacs on Windows

[Robert Pluim]

>>>>> On Mon, 11 Oct 2021 04:56:43 -0700, Stefan Kangas <stefan@marxist.se> 
>>>>> said:

    Stefan> Eli Zaretskii <eliz@gnu.org> writes:
    >>> From: Robert Pluim <rpluim@gmail.com>
    >>> Cc: Eli Zaretskii <eliz@gnu.org>,  45821@debbugs.gnu.org
    >>> Date: Mon, 27 Sep 2021 18:47:47 +0200
    >>> 
    >>> Iʼve resurrected this patch, it seems to be working nicely. Adding a
    >>> lisp-level control variable seems more trouble than itʼs worth, I
    >>> think the risk of breaking stuff on all platforms is higher than
    >>> that of breaking stuff on Windows.
    >>> 
    >>> Are we too late for emacs-28?
    >> 
    >> Yes, please wait until the release branch is cut.

    Stefan> I guess it's time to push this to master now?

No, because it breaks TLS connections.

I am in fact amazed that the existing code works at all on MS-Windows,
since we end up doing multiple 1-byte reads whilst also doing
gnutls_try_handshake, but work it does. And this patch doesnʼt.

Robert
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