Socket Programming Question:

A socket is a communications connection point (endpoint) that you can name and address in a network. The processes that use a socket can reside on the same system or on different systems on different networks. Sockets are useful for both stand-alone and network applications.

Sockets commonly are used for client/server interaction. Typical system configuration places the server on one machine, with the clients on other machines. The clients connect to the server, exchange information, and then disconnect.

Socket characteristics:
. A socket is represented by an integer. That integer is called a socket descriptor.
. A socket exists as long as the process maintains an open link to the socket.
. You can name a socket and use it to communicate with other sockets in a communication domain.
. Sockets perform the communication when the server accepts connections from them, or when it exchanges messages with them.
.You can create sockets in pairs.
The connection that a socket provides can be connection-oriented or connectionless.
Connection-oriented communication implies that a connection is established, and a dialog between the programs will follow. The program that provides the service (the server program) establishes the connection. It assigns itself a name that identifies where to obtain that service. The client of the service (the client program) must request the service of the server program. The client does this by connecting to the distinct name that the server program has designated. It is similar to dialing a telephone number (an identifier) and making a connection with another party that is offering a service (for example, a plumber). When the receiver of the call (the server) answers the telephone, the connection is established. The plumber verifies that you have reached the correct party, and the connection remains active as long as both parties require it.
Connectionless communication implies that no connection is established over which a dialog or data transfer can take place. Instead, the server program designates a name that identifies where to reach it (much like a post office box). By sending a letter to a post office box, you cannot be absolutely sure the letter is received. You may have to send another letter to reestablish communication.