JAVA-MANI.BLOGSPOT.COM

In this example you'll see how to create a client-server socket communication. The example below consist of two main classes, the ServerSocketExample and the ClientSocketExample. The server application listen to port 7777 at the localhost. When we send a message from the client application the server receive the message and send a reply to the client application.

The communication in this example using the TCP socket, it means that there is a fixed connection line between the client application and the server application.


package org.kodejava.example.net;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.ClassNotFoundException;
import java.lang.Runnable;
import java.lang.Thread;
import java.net.ServerSocket;
import java.net.Socket;

public class ServerSocketExample {
private ServerSocket server;
private int port = 7777;

public ServerSocketExample() {
try {
server = new ServerSocket(port);
} catch (IOException e) {
e.printStackTrace();
}
}

public static void main(String[] args) {
ServerSocketExample example = new ServerSocketExample();
example.handleConnection();
}

public void handleConnection() {
System.out.println("Waiting for client message...");

//
// The server do a loop here to accept all connection initiated by the
// client application.
//
while (true) {
try {
Socket socket = server.accept();
new ConnectionHandler(socket);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

class ConnectionHandler implements Runnable {
private Socket socket;

public ConnectionHandler(Socket socket) {
this.socket = socket;

Thread t = new Thread(this);
t.start();
}

public void run() {
try
{
//
// Read a message sent by client application
//
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
String message = (String) ois.readObject();
System.out.println("Message Received: " + message);

//
// Send a response information to the client application
//
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
oos.writeObject("Hi...");

ois.close();
oos.close();
socket.close();

System.out.println("Waiting for client message...");
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}

package org.kodejava.example.net;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.ClassNotFoundException;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;

public class ClientSocketExample {
public static void main(String[] args) {
try {
//
// Create a connection to the server socket on the server application
//
InetAddress host = InetAddress.getLocalHost();
Socket socket = new Socket(host.getHostName(), 7777);

//
// Send a message to the client application
//
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
oos.writeObject("Hello There...");

//
// Read and display the response message sent by server application
//
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
String message = (String) ois.readObject();
System.out.println("Message: " + message);

ois.close();
oos.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}


To test the application you need to start the server application. Each time you run the client application it will send a message "Hello There..." and in turns the server reply with a message "Hi...".