@Vinnie Falco Thanks.  

Now it builds successfully, but I have this output in the server app console:

"
Starting server at 0.0.0.0:5501...
Lines 625 and 626:
handshake: Lines 625 and 626:
handshake: An existing connection was forcibly closed by the remote host
An existing connection was forcibly closed by the remote hostLines 646 and 647:
read: An existing connection was forcibly closed by the remote host

Lines 646 and 647:
read: An existing connection was forcibly closed by the remote host
Lines 625 and 626:
handshake: Lines 625 and 626:
handshake: An existing connection was forcibly closed by the remote host
An existing connection was forcibly closed by the remote host
Lines 646 and 647:
read: Lines 646 and 647:
read: An existing connection was forcibly closed by the remote host
An existing connection was forcibly closed by the remote host
"

I've been having this problem since before I tried to move the app to C++20.  I tried taking it out of Firewall exceptions and adding it back in because I read somewhere that that could help in some cases, but no luck.  Then I thought maybe upgrading to the latest version of Boost and OpenSSL will help, so I tried that too, but again no luck.  My port forwarding has no issues either, and I've also renewed my SSL certs.  So what could the problem be?  Anyone got any ideas?

If this isn't an issue I should ask about here, where would be better?  Some networking forum or something?