Typical BSD Sockets applications consist of two separate application level
processes; one process (the client)
requests a connection and the other process (the server
)
accepts it.
The server process creates a socket, binds an address to it,
and sets up a mechanism (called a listen queue) for receiving connection
requests. The client process creates a socket and requests a connection
to the server process. Once the server process accepts a client
process's request and establishes a connection, full-duplex (two-way)
communication can occur between the two sockets.
This set of conventions must be implemented by both processes.
Depending upon the needs of your application, your implementation
of the model can be symmetric or asymmetric. In a symmetrical application
of the model, either process can be a server or a client. In an
asymmetrical application of the model, there is a clearly defined
server process and client process. An example of an asymmetrical
application is the ftp service.
Creating a Connection: the Client-Server Model |
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The following figures illustrate conceptual views of the client-server
model at three different stages of establishing a connection. The
completed steps are included in each figure.
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