Socket Programming in Java

1. Introduction

Socket programming in Java allows communication between devices over a network. It uses the TCP/IP protocol suite, enabling reliable, ordered, and error-checked delivery of a stream of bytes.

2. Key Concepts

• Socket: An endpoint for sending or receiving data.
• Server Socket: Listens for incoming connections.
• Client Socket: Connects to a server socket.
• Port: A communication endpoint for applications.
• IP Address: Identifies a device on the network.

3. Client-Server Model

The client-server model is a distributed application structure that partitions tasks between service providers (servers) and service requesters (clients).

                graph TD;
                    A[Client] -->|Connects| B[Server];
                    B -->|Sends Data| A;
            

4. Socket Creation

To create a socket in Java, follow these steps:

1. Import the required packages:
2. Create a socket using new Socket(host, port).
3. Use input/output streams to read/write data.
4. Close the socket after communication is finished.

5. Code Example

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

public class Server {
    public static void main(String[] args) {
        try (ServerSocket serverSocket = new ServerSocket(12345)) {
            System.out.println("Server listening on port 12345");
            Socket socket = serverSocket.accept();
            System.out.println("Client connected");

            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            String message = in.readLine();
            System.out.println("Received: " + message);
            out.println("Hello Client!");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
                

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

public class Client {
    public static void main(String[] args) {
        try (Socket socket = new Socket("localhost", 12345)) {
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out.println("Hello Server!");
            String response = in.readLine();
            System.out.println("Server replied: " + response);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
                

6. Best Practices

• Always close sockets in a finally block or use try-with-resources.
• Handle exceptions properly to avoid unexpected crashes.
• Use a separate thread for each client to handle multiple clients simultaneously.
• Implement timeouts to enhance the robustness of your application.

7. FAQ