TCP Features : Multiplexing

TCP enables many processes within a single computer to use the TCP communications services simultaneously; this is called TCP multiplexing. Because these processes may be communicating over the same network interface, they are identified by the IP address of the network interface. However, you need more than the IP address of the network interface to identify a process because all processes that are using the same network interface on a computer have a common IP address.
TCP associates a port number value for applications that use TCP. This association enables several connections to exist between application processes on remote computers because each connection uses a different pair of port numbers.

This picture shows several connections being multiplexed over TCP.
The binding of ports to application processes is handled independently by each computer. In many computer systems, a logger or super daemon process watches over the port numbers that are identified or well known to other computer systems.