In Java networking, various methods are used to establish communication between two or more devices across a network. Here are the most common types:

1.Socket Programming (TCP/IP)

Definition:

  • Socket programming is based on the TCP/IP protocol, which provides reliable, connection-oriented communication between a client and a server. The server listens for incoming connections, and the client initiates the connection.

Example

// Server (run first)
import java.io.*;
import java.net.*;

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8080);
        System.out.println("Server started, waiting for client...");
        Socket socket = serverSocket.accept();
        System.out.println("Client connected");

        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String clientMessage = in.readLine();
        System.out.println("Client says: " + clientMessage);

        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
        out.println("Hello from Server");

        socket.close();
        serverSocket.close();
    }
}

// Client (run second)
import java.io.*;
import java.net.*;

public class Client {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket("localhost", 8080);
        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
        out.println("Hello Server");

        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String serverMessage = in.readLine();
        System.out.println("Server says: " + serverMessage);

        socket.close();
    }
}

 

Output:

Server:
Server started, waiting for client...
Client connected
Client says: Hello Server

Client:
Server says: Hello from Server

Advantages:

  • Provides reliable and ordered communication.
  • Connection-oriented, meaning that both sides ensure data is received correctly.

Uses:

  • Web servers and web browsers.
  • Remote command execution.
  • File transfer between client and server.

2.Datagram (UDP) Programming

Definition:

  • Datagram programming uses the UDP (User Datagram Protocol), which is connectionless and does not guarantee the delivery or ordering of packets. It’s faster but less reliable than TCP.

Example:

// Server (run first)
import java.net.*;

public class UDPServer {
    public static void main(String[] args) throws Exception {
        DatagramSocket serverSocket = new DatagramSocket(9876);
        byte[] receiveData = new byte[1024];
        DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
        System.out.println("Server waiting for data...");
        serverSocket.receive(receivePacket);
        String message = new String(receivePacket.getData(), 0, receivePacket.getLength());
        System.out.println("Received from client: " + message);
        serverSocket.close();
    }
}

// Client (run second)
import java.net.*;

public class UDPClient {
    public static void main(String[] args) throws Exception {
        DatagramSocket clientSocket = new DatagramSocket();
        InetAddress IPAddress = InetAddress.getByName("localhost");
        byte[] sendData = "Hello UDP Server".getBytes();
        DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
        clientSocket.send(sendPacket);
        clientSocket.close();
    }
}

 

Output:

Server:
Server waiting for data...
Received from client: Hello UDP Server

Advantages:

  • Faster than TCP since it has no overhead for establishing connections.
  • Suitable for time-sensitive applications.

Uses:

  • Real-time gaming.
  • Video streaming.
  • Voice-over-IP (VoIP).

3.URL (Uniform Resource Locator)

Definition:

  • A URL is used to identify resources on the internet. The URL class in Java provides methods to fetch data from web resources over HTTP or HTTPS.

Example:

import java.io.*;
import java.net.*;

public class URLExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://www.example.com");
        BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println(inputLine);
        }
        in.close();
    }
}

Output:

(Displays the HTML content of the webpage: "https://www.example.com")

Advantages:

  • Easy to interact with web resources.
  • Can handle different protocols like HTTP, HTTPS, and FTP.

Uses:

  • Web scraping.
  • Fetching content from APIs.
  • Downloading files from the internet.

4.Multicast

Definition:

  • Multicasting allows sending data to multiple recipients simultaneously using the UDP protocol. Java supports multicast communication using the MulticastSocket class.

Example:

// Sender
import java.net.*;
public class MulticastSender {
    public static void main(String[] args) throws Exception {
        MulticastSocket socket = new MulticastSocket();
        InetAddress group = InetAddress.getByName("230.0.0.1");
        byte[] message = "Hello Multicast Group".getBytes();
        DatagramPacket packet = new DatagramPacket(message, message.length, group, 6789);
        socket.send(packet);
        socket.close();
    }
}

// Receiver
import java.net.*;

public class MulticastReceiver {
    public static void main(String[] args) throws Exception {
        MulticastSocket socket = new MulticastSocket(6789);
        InetAddress group = InetAddress.getByName("230.0.0.1");
        socket.joinGroup(group);
        byte[] buffer = new byte[1000];
        DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
        socket.receive(packet);
        String message = new String(packet.getData(), 0, packet.getLength());
        System.out.println("Received: " + message);
        socket.leaveGroup(group);
        socket.close();
    }
}

Output:

Receiver:
Received: Hello Multicast Group

 

Advantages:

  • Efficient for sending data to multiple recipients without duplication.
  • Reduces bandwidth usage for large-scale broadcasting.

Uses:

  • Video conferencing.
  • Live streaming.
  • Distributed systems.

5.Remote Method Invocation (RMI)

Definition:

  • Remote Method Invocation (RMI) enables a Java program to invoke methods of objects residing on different JVMs. It allows distributed applications to communicate and share resources across the network.

Example:

// Interface (shared by both client and server)
import java.rmi.*;

public interface MyRemote extends Remote {
    String sayHello() throws RemoteException;
}

// Server
import java.rmi.*;
import java.rmi.server.*;

public class MyRemoteImpl extends UnicastRemoteObject implements MyRemote {
    public MyRemoteImpl() throws RemoteException {}
    public String sayHello() {
        return "Hello from Server";
    }

    public static void main(String[] args) {
        try {
            Naming.rebind("RemoteHello", new MyRemoteImpl());
            System.out.println("Server ready");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

// Client
import java.rmi.*;

public class MyRemoteClient {
    public static void main(String[] args) {
        try {
            MyRemote service = (MyRemote) Naming.lookup("rmi://localhost/RemoteHello");
            System.out.println(service.sayHello());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Output:

Server:
Server ready

Client:
Hello from Server

Advantages:

  • Allows seamless method calls over a network, making remote objects behave like local ones.
  • Simplifies distributed application development.

Uses:

  • Distributed applications.
  • Remote database access.
  • Enterprise-level applications.

Categorized in:

Java

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