Sockets, which provide a mechanism for communication between two computers.The socket is the software abstraction used to represent the "terminals" of a connection

between two machines. For a given connection, there s a socket on each machine, and you

can imagine a hypothetical "cable" running between the two machines with each end of the

"cable" plugged into a socket. Of course, the physical hardware and cabling between

machines is completely unknown. The whole point of the abstraction is that we don t have to

know more than is necessary.