What is socket programming? Write down client/server chat program using TCP.

 Socket programming is a way of communicating between two applications over a network using sockets. It allows two or more applications to send and receive data over a network connection.

Here is an example of a simple client/server chat program using TCP sockets in Java:

Server Side:

import java.io.*;

import java.net.*;
public class ChatServer {
    public static void main(String[] args) {
        try {
            // Create a server socket that listens on port 5000
            ServerSocket serverSocket = new ServerSocket(5000);
            // Wait for a client to connect
            System.out.println("Waiting for a client to connect...");
            Socket clientSocket = serverSocket.accept();
            System.out.println("Client connected: " + clientSocket.getInetAddress().getHostAddress());
            // Create input and output streams
            BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
            // Start chatting with the client
            String inputLine;
            while ((inputLine = in.readLine()) != null) {
                System.out.println("Client: " + inputLine);
                out.println("Server: " + inputLine);
            }
            // Close the streams and sockets
            in.close();
            out.close();
            clientSocket.close();
            serverSocket.close();
        } catch (IOException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}

Client Side:

import java.io.*;
import java.net.*;
public class ChatClient {
    public static void main(String[] args) {
        try {
            // Connect to the server on port 5000
            Socket socket = new Socket("localhost", 5000);
            // Create input and output streams
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            // Start chatting with the server
            BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
            String inputLine, outputLine;
            while ((inputLine = console.readLine()) != null) {
                out.println(inputLine);
                outputLine = in.readLine();
                System.out.println("Server: " + outputLine);
            }
            // Close the streams and socket
            in.close();
            out.close();
            socket.close();
        } catch (IOException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}

In this program, the server listens on port 5000 for a client to connect. Once a client connects, the server creates input and output streams and starts a loop to read messages from the client and send responses back. The client connects to the server on localhost and port 5000 and creates its own input and output streams. It then starts a loop to read messages from the user and send them to the server, and to read responses from the server and display them to the user.

This program uses TCP sockets, which provide reliable, ordered, and error-checked delivery of data between applications. It demonstrates how to create and use sockets, input and output streams, and how to handle exceptions that may occur during socket communication.