[ntcore] Server crashes on Windows with v4.1 connections

[jwbonner]

Connecting using the 4.1 protocol to an NT server running on Windows (2024.1.1-beta-1) causes a crash like this:

NT: Got a NT4 connection from 192.168.0.202 port 57874
NT: CONNECTED NT4 client 'outlineviewer@1' (from 192.168.0.202:57874)
NT: DISCONNECTED NT4 client 'outlineviewer@1' (from 192.168.0.202:57874): stream error: EAGAIN
NT: NT4 socket error: resource temporarily unavailable

This occurs without a separate RTT connection, and doesn't occur when connecting using the 4.0 protocol even on the current version of the server. I've recreated this using AdvantageScope on localhost (Windows), AdvantageScope on a remote device (macOS), and OutlineViewer on a remote device (macOS). OutlineViewer running on localhost (Windows) crashes the client but not the server, presumably with a similar error on the client.

None of this occurs when running the NT server on macOS (except for crashing the client when connecting from OutlineViewer on Windows). I haven't tested on Linux.

Related to Mechanical-Advantage/AdvantageScope#97.

[PeterJohnson]

Fixed by #5788 and kin.