Connection Multiplexing

Supposing we have opened a connection of type either TCP or UDP to another remote machine. Having this connection, can we allow multiple connections virtually over this connection like VPN(but not VPN)? I mean multiple applica开发者_运维知识库tions run on remote machine and you try to access to these applications, is there any multiplexing mechanism or concept supporting such feature?

That is also known as tunneling protocol, and various applications implement that for various protocols. I personally like OpenSSH - see here.