For a web server, one can purchase a certificate from a CA to provide secure connection (server authentication and data encryption).
But in cases of remote desktop apps like MS Remote Desktop or TeamViewer, how do they establish a secure connection between the remote client and the target PC?
It seems in this case the target PC is a sort of server, so it must have a domain name and a certificate to provide TLS, right? But in most cases it is likely that the target PC does not have a domain name nor a certificate.
Is there any other way to establish a secure connection in this case?