For client side this will return the #GTlsClientConnection when connected
over TLS.
For server side connections, this function will create a GTlsServerConnection
when called the first time and will return that same connection on subsequent
calls. The server is then responsible for configuring the TLS connection.
Get the TLS connection of conn.
For client side this will return the #GTlsClientConnection when connected over TLS.
For server side connections, this function will create a GTlsServerConnection when called the first time and will return that same connection on subsequent calls. The server is then responsible for configuring the TLS connection.