TCP Communication Demo

Client.java

import java.io.*;
import java.net.*;
import java.util.Scanner;

public class Client {
    public static void main(String[] args) throws IOException {
        String ip = "10.0.0.20"; // obtain using server's ipconfig (windows), ifconfig (mac, linux)
        int port = 1234; // obtain the server's port

        var socket = new Socket(ip, port);

        var socketIn = socket.getInputStream();

        var systemScanner = new Scanner(System.in);
        var socketScanner = new Scanner(socketIn);

        var socketOut = new PrintStream(socket.getOutputStream(), true);

        System.out.println("Please enter your username:");

        String username = systemScanner.nextLine();
        String prefix = "<" + username + ">: ";

        System.out.println("\nWelcome to the chatroom! Type a message and press enter to send it.");

        while (true) {
            if (System.in.available() > 0) {
                String message = systemScanner.nextLine();
                System.out.println(prefix + message); // print to own console
                socketOut.println(prefix + message); // print to server socket
            }

            if (socketIn.available() > 0){
                String message = socketScanner.nextLine();
                System.out.println(message); // print to own console
            }
        }
    }
}

Server.java

import java.io.IOException;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.util.Scanner;

public class Server {
    public static void main(String[] args) throws IOException {
        // my device's ip: 10.0.0.20
        // find using ifconfig on mac, ipconfig on windows

        int port = 1234;

        var serverSocket = new ServerSocket(port);
        var socket = serverSocket.accept();

        var socketIn = socket.getInputStream();

        var systemScanner = new Scanner(System.in);
        var socketScanner = new Scanner(socketIn);

        var socketOut = new PrintStream(socket.getOutputStream(), true);

        System.out.println("Please enter your username:");
        String username = systemScanner.nextLine();

        String prefix = "<" + username + ">: ";

        System.out.println("\nWelcome to the chatroom! Type a message and press enter to send it.");

        while (true) {
            if (System.in.available() > 0) {
                String message = systemScanner.nextLine();
                System.out.println(prefix + message); // print to own console
                socketOut.println(prefix + message); // print to server socket
            }

            if (socketIn.available() > 0){
                String message = socketScanner.nextLine();
                System.out.println(message); // print to own console
            }
        }
    }
}

To find your local IP address, run ipconfig in the windows terminal or ifconfig on mac/linux, and search for the IP address associated with the en0 network interface.