Most companies
these days have a telephone switchboard that acts as a gateway for
calls coming in and going out. A socket can be likened to a telephone
switchboard. If you want to connect to a remote host, you need to
first create a socket through which the communications occur. This
is similar to dialing "9" to go through the switchboard to the outside
world.
Similarly, if you want to create a server that accepts connections
from remote (or local) hosts, you need to set up a socket that "listens"
periodically for connections. The socket is identified on the Internet
by the host's IP address and the "port" that it listens on. Once
a connection is established, a new socket is created to handle this
connection, so that the original socket can go back and listen for
more connections. The switchboard works in the same manner: as it
handles outside phone calls, it routes them to the appropriate extension
and goes back to accept more calls.
