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Client Socket example

The client program establishes a connection to the server program on a particular host and port number in its listenSocket method, and sends the data entered by the end user to the server program in its actionPerformed method. The actionPerformed method also receives the data back from the server and prints it to the command line.

listenSocket Method
The listenSocket method first creates a Socket object with the computer name (kq6py) and port number (4321) where the server program is listening for client connection requests. Next, it creates a PrintWriter object to send data over the socket connection to the server program. It also creates a BufferedReader object to read the text sent by the server back to the client. 

public void listenSocket(){
//Create socket connection
   try{
     socket = new Socket("kq6py.eng", 4321);
     out = new PrintWriter(socket.getOutputStream(), true);
     in = new BufferedReader(new InputStreamReader(
				socket.getInputStream()));
   } catch (UnknownHostException e) {
     System.err.println("Unknown host: kq6py.eng");
     System.exit(1);
   } catch  (IOException e) {
     System.err.println("No I/O");
     System.exit(1);
   }
}

actionPerformed Method
The actionPerformed method is called by the Java platform for action events such as button clicks. This actionPerformed method code gets the text in the Textfield object and passes it to the PrintWriter object, which then sends it over the socket connection to the server program. The actionPerformed method then makes the Textfield object blank so it is ready for more end user input. Lastly, it receives the text sent back to it by the server and prints the text out. 

public void actionPerformed(ActionEvent event){
   Object source = event.getSource();

   if(source == button){
//Send data over socket
      String text = textField.getText();
      out.println(text);
      textField.setText(new String(""));
      out.println(text);
   }
//Receive text from server
   try{
     String line = in.readLine();
     System.out.println("Text received: " + line);
   } catch (IOException e){
     System.err.println("Read failed");
     System.exit(1);
   }
}

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