I found this open bug:
https://issuetracker.google.com/issues/80149140
and their suggested workaround works for me!
The easiest way of doing this is to run the emulator with the additional parameters:
-feature -Wifi
So launching my emulator is something like this:
cd "C:Program Files (x86)Androidandroid-sdkemulator"
./emulator.exe -avd tablet_m-dpi_10_1in_-_api_28 -feature -Wifi
And pay close attention that its -Wifi (lowercase f and with a hyphen). You can get a list of your devices by using the command:
./emulator.exe -list-avds
And you still need to do the telnet bit after the emulator is running:
telnet localhost 5554
auth <your+code+here>
redir add udp:8000:8000
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