title: Distinguishing between multiple clients behind the same NAT
body: <p>I have a Server X and 2 clients A and B behind the same NAT. A and B need to form 10 TCP connections each to X on the same outbound port. X should only accept at most 10 connections from a single client. So I need X to tell A from B right after accept().
  Is there any way to do this with just the information in a TCP packet or do or do I have to have the client send the server some unique ID after the connection is established?</p>