Sockets and You

				



It seems we meet again. Or for the first time perhaps?
Either way, I’ve come to enjoy your company. So lets talk over some Java. Remember
to include the java.net and java.io packages!
 
You want to learn about sockets? Here are there basic steps
to help that go throw the connection process:
 
1) Server (Tim)
- Creates a new socket listening on port 4444. 
 
2)Client (Chris)
– Creates a new socket connecting to Tim on port
4444.
 
3) Data
transfer begins.
 
 
Initializing a client socket looks like this.
 
Socket clientSocket
= null;
clientSocket = new Socket("Tim", 4444);
 
This socket is connecting to a computer called Tim on
port 4444. Now, Tim can be either the name of a
computer on a network or an IP address. But before a client connects to a
server socket, there has to be a server socket.
 
Socket serverSocket
= null;
serverSocket = new Socket(4444);
//Notice no user to connect to this time.
serverSocket.accept(); //Accept a client.
 
Not too
hard is it? Now lets explain step three: Data Transfer.
 
From the
socket you must receive input and you must send output. Clear? Good. To do this
you must declare a PrintWriter for output and a BufferedReader
for input. The following good is used for both a client and a server
socket. For the sake of simplicity I will use a client socket.
 
PrintWriter out = null;
BufferedReader in = null;
Socket clientSocket
= null;
 
clientSocket = new Socket("Tim", 4444);
out = new PrintWriter(clientSocket.getOutputStream(),
true); //get the socket’s ouput
in = new BufferedReader( new inputStreamReader( clientSocket.getInputStream() ) ); //get the socket’s input
 
Looking
back, I think I overdid the color. Oh well. All you really need to look at are
the last two lines. The PrintWriter out will be the new front door for the
socket’s output. Calling out.println(“Hello”) would
send the string hello to the server. Not too hard. I am going to
finish this showing you how to use a loop to receive information. 
 
PrintWriter out = null;
BufferedReader in = null;
Socket clientSocket
= null;
String fromServer;

 
 
clientSocket = new Socket("Tim", 4444);
out = new PrintWriter(clientSocket.getOutputStream(),
true); 
in = new BufferedReader(new inputStreamReader( clientSocket.getInputStream() ) );
 
while ((fromServer = in.readLine()) != null) { //Loop
while we are still getting messages

            System.out.println("Server: " + fromServer); //Display message we got

            

                }
            
            out.close();

      in.close();

      clientSocket.close();

 
I know right now some people aren’t going to understand this
article. If you read it and don’t know how to make a chat program then you need
to read some more tutorials. I suggest going to http://java.sun.com/
for more help. Email me with feedback type stuff – Tim Fischer