I discovered OpenSSL was returning the following error:
error:140C5042:SSL routines:SSL_UNDEFINED_FUNCTION:called a function you should not call
I learned this was because U++ is using SSLv3_client_method() when creating a context. As this code is the server side, I had to change it to SSLv3_server_method()
Now I'm having new errors, but I believe those are related to certificates and keys.