java Network programming using socket(1)

Java supports stream-based communication and packet-based communication,and the first is universal.
Create ServerSocket
1.Create ServerSocket

ServerSocket serverSocket=new ServerSocket(port);

2.Listen to the connect

Socket socket=serverSocket.accept();

3.We need create InputStream and OutputStream to transmit data

InputStream inputFromClient=socket.getInputSream();
OutputStream outputToClient=socket.getOutputStream();

(we can also use DataInputStream and DataOutputStream ,BufferedReader and PrintWriter to get the data types are int,double and string.)

Create client Socket
1.Create client Socket

Socket socket=new Socket(serverName,port);

(the serverName can be host name or the host IP address.)
2.We need create InputStream and OutputStream to transmit data

InputSream inputFromServer=socket.getInputStream();
OutputStream outputToServer=socket.getOutputStream();

(we can also use DataInputStream and DataOutputStream ,BufferedReader and PrintWriter to get the data type are int,double or string.)

Now,there is an example that Client send radius to Server and Server compute area and return to Client.

Server.java

import java.awt.BorderLayout;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class Server extends JFrame {
    private JTextArea jta=new JTextArea();

    public static void main(String[] args) {
        new Server();
    }

    public Server() {
        setLayout(new BorderLayout());
        add(new JScrollPane(jta),BorderLayout.CENTER);

        setTitle("Server");
        setSize(500,300);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);

        try{
            //Create a server socket
            ServerSocket serverSocket=new ServerSocket(8000);
            jta.append("Server started at "+new Date() +"\n");

            //Listen for a connection request
            Socket socket=serverSocket.accept();

            //Create data input and output streams
            DataInputStream inputFromClient=new DataInputStream(socket.getInputStream());
            DataOutputStream outputToClient=new DataOutputStream(socket.getOutputStream());

            while (true) {
                //Receive radius from the client
                double radius=inputFromClient.readDouble();

                //Compute area
                double area=radius*radius*Math.PI;

                //Send area back to the client
                outputToClient.writeDouble(area);

                jta.append("Radius received from client:"+radius +‘\n‘);
                jta.append("Area found:" +area+‘\n‘);
            }
        }
        catch(IOException ex){
            System.err.println(ex);
        }

    }
}

Client.java

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;



public class Client extends JFrame {
    //Text filed for receiving radius
    private JTextField jtf=new JTextField();

    //Text area to display contents
    private JTextArea jta=new JTextArea();

    //IO streams
    private DataOutputStream toServer;
    private DataInputStream fromServer;

    public static void main(String[] args) {
        new Client();
    }

    public Client(){
        //Panel panel to hold the label and text field 
        JPanel panel=new JPanel();
        panel.setLayout(new BorderLayout());
        panel.add(new JLabel("Enter radius"),BorderLayout.WEST);
        panel.add(jtf,BorderLayout.CENTER);
        jtf.setHorizontalAlignment(JTextField.RIGHT);

        setLayout(new BorderLayout());
        add(panel,BorderLayout.NORTH);
        add(new JScrollPane(jta),BorderLayout.CENTER);

        jtf.addActionListener(new TextFieldListener());

        setTitle("Client");
        setSize(500,300);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);//It is necessary to show the frame here

        try {
            //Create a socket to connect to the server
            Socket socket=new Socket("localhost",8000);
            //Socket socket =new Socket("130.254.204.36",8000);
            //Socket socket =new Socket("drake.Armstrong.edu",8000);
            System.out.println("local port: "+socket.getLocalPort());

            //Test InetAddress
            InetAddress inetAddress=socket.getInetAddress();
            System.out.println("Client‘s host name is "+inetAddress.getHostName());
            System.out.println("Client‘s IP Address is "+inetAddress.getHostAddress());
            //


            //Create an input stream to receive data from the server
            fromServer=new DataInputStream(socket.getInputStream());

            //Create an output stream to send data from the server
            toServer=new DataOutputStream(socket.getOutputStream());

        } catch (IOException ex) {
            jta.append(ex.toString()+‘\n‘);
        }
    }

    private class TextFieldListener implements ActionListener{
        public void actionPerformed(ActionEvent e) {
            try {
                //get the radius from the text field
                double radius=Double.parseDouble(jtf.getText().trim());

                //Send the radius to the server
                toServer.writeDouble(radius);
                toServer.flush();

                //Get area from the server
                double area=fromServer.readDouble();

                //display to the text server
                jta.append("Radius is "+radius+"\n");
                jta.append("Area received from the server is "+area +‘\n‘);


            } catch (IOException ex) {
                System.err.println(ex);
            }

        }
    }
}