Java Reference
In-Depth Information
Sidebar 14.1 Sockets
Sockets are the standard tool used for communicating over a computer network. Sockets are a
flexible tool and support a large spectrum of communication protocols, the most common being
those in the TCP IP framework.
We will focus on the TCP protocol. There are two classes that are used to establish and carry out
normal TCP connections: ServerSocket and Socket . For simple connections between a client and a
server they are likely to be sufficient.
ServerSocket represents the socket on a server that waits and listens for requests for service from
a client. Socket represents the endpoints for communication between a server and a client. When
a server gets a request for service, it creates a Socket for communication with the client and
continues to listen for other requests on the ServerSocket . The client also creates a Socket for
communication with the server. The sequence is shown below in Figure 14.15 (from the Sun Java
Networking Overview).
Server application
network connection
Client Application
server : ServerSocket
client_side : Socket
server_side : Socket
the accept() method
blocks the caller until
a connection has
been established
The two sockets are
now connected
Figure 14.15 Setup of a socket connection
Once the connection is established, getInputStream() and getOutputSteam() may be used in com-
munication between the sockets. A sample server program is the following:
ServerSocket server # new ServerSocket(SERVER_PORT);
Socket socket # server.accept();
InputStream in # socket. getInputStream();
OutputStream out # socket. getOutputStream();
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