Basic Sockets

Networking is built into the Java language and part of the java.net package (think import).

Java has the URL class for representing a resource on the World Wide Web.

Networking support in Java includes sockets, which is used for coding client/server communication.

A very useful class for using sockets is the Sockets class.

Once a Socket connection is established, communication is done through streams with standard I/O.

For getting information from the server, you can use socketObj.getInputStream() to create a BufferedReader, then call the readLine() method.

For sending information to the server, use socketObj.getOutputStream() to create a PrintWriter, then call the println() method.

Another mechanism for sockets communication is to use datagrams and not maintain the connection (like a Socket does).

You can create a simple client Socket with: Socket s = new Socket("hostname", portNumber);

Once you have the Socket, get an input stream for reading data with code like this: InputStream in = s.getInputStream();

Once you have the Socket, get an output stream for writing with code like this: OutputStream out = s.getOutputStream();

The server Socket is created with the ServerSocket class.