How to Build a Java Chat Application – Step-by-Step Guide | CodeHelping

Posted on By Omkar Pathak No Comments on How to Build a Java Chat Application – Step-by-Step Guide | CodeHelping
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In this tutorial, you’ll learn how to build a Java chat Application system using Java sockets.
This project is perfect for college, this project will teach you the concept of client-server communication in Java Chat App.

How to Build a Java Chat Application – Step-by-Step Guide

Let’s Create this Java Chat Application.

  1. Open Eclipse and create a new project named ChatApp (or any name of your choice).
  2. Inside the project, create a package with the same name: ChatApp.
  3. Add two Java files to this package: Client.java and Server.java.
  4. Now, paste the following code into the respective files.

Client Java Code:

package chatapp;

import java.io.*;
import java.util.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.text.*;
import java.net.*;
import javax.swing.border.*;

public class Client implements ActionListener {
    
    JTextField text;
    static JPanel a1;
    static Box vertical = Box.createVerticalBox();
    static JFrame f = new JFrame();
    static DataOutputStream dout;
    
    public static JPanel formatLabel(String out) {
        JPanel panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        
        JLabel output = new JLabel("<html><p style=\"width: 150px\">" + out + "</p></html>");
        output.setFont(new Font("Tahoma", Font.PLAIN, 16));
        output.setBackground(new Color(227, 250, 248));
        output.setOpaque(true);
        output.setBorder(new EmptyBorder(15, 15, 15, 50));
        panel.add(output);
        Calendar cal = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm");
        JLabel time = new JLabel();
        time.setText(sdf.format(cal.getTime()));
        panel.add(time);
        return panel;
    }
    
    public void actionPerformed(ActionEvent ae) {
        try {
            String out = text.getText();
            JPanel p2 = formatLabel(out);
            a1.setLayout(new BorderLayout());
            JPanel right = new JPanel(new BorderLayout());
            right.add(p2, BorderLayout.LINE_END);
            vertical.add(right);
            vertical.add(Box.createVerticalStrut(15));
            a1.add(vertical, BorderLayout.PAGE_START);
            dout.writeUTF(out);
            text.setText("");
            f.repaint();
            f.invalidate();
            f.validate();   
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) {
        new Client();
        try {
            //object of the class Socket
            Socket s = new Socket("127.0.0.1", 6001);
            DataInputStream din = new DataInputStream(s.getInputStream());
            dout = new DataOutputStream(s.getOutputStream());
            while(true) {
                a1.setLayout(new BorderLayout());
                String msg = din.readUTF();
                JPanel panel = formatLabel(msg);
                JPanel left = new JPanel(new BorderLayout());
                left.add(panel, BorderLayout.LINE_START);
                vertical.add(left);
                vertical.add(Box.createVerticalStrut(15));
                a1.add(vertical, BorderLayout.PAGE_START);
                f.validate();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    Client() {
        f.setLayout(null);
        JPanel p1 = new JPanel();
        p1.setBackground(new Color(37, 147, 211));
        p1.setBounds(0, 0, 450, 70);
        p1.setLayout(null);
        f.add(p1);
        ImageIcon i1 = new ImageIcon(ClassLoader.getSystemResource("icons/3.png"));
        Image i2 = i1.getImage().getScaledInstance(25, 25, Image.SCALE_DEFAULT);
        ImageIcon i3 = new ImageIcon(i2);
        JLabel back = new JLabel(i3);
        back.setBounds(5, 20, 25, 25);
        p1.add(back);
        back.addMouseListener(new MouseAdapter() {
            public void mouseClicked(MouseEvent ae) {
                System.exit(0);
            }
        });
        
        ImageIcon i4 = new ImageIcon(ClassLoader.getSystemResource(""));
        Image i5 = i4.getImage().getScaledInstance(50, 50, Image.SCALE_DEFAULT);
        ImageIcon i6 = new ImageIcon(i5);
        JLabel profile = new JLabel(i6);
        profile.setBounds(40, 10, 50, 50);
        p1.add(profile);
        
        ImageIcon i7 = new ImageIcon(ClassLoader.getSystemResource("images/video.png"));
        Image i8 = i7.getImage().getScaledInstance(30, 30, Image.SCALE_DEFAULT);
        ImageIcon i9 = new ImageIcon(i8);
        JLabel video = new JLabel(i9);
        video.setBounds(300, 20, 30, 30);
        p1.add(video);
        
        ImageIcon i10 = new ImageIcon(ClassLoader.getSystemResource("images/phone.png"));
        Image i11 = i10.getImage().getScaledInstance(35, 30, Image.SCALE_DEFAULT);
        ImageIcon i12 = new ImageIcon(i11);
        JLabel phone = new JLabel(i12);
        phone.setBounds(360, 20, 35, 30);
        p1.add(phone);
        
        ImageIcon i13 = new ImageIcon(ClassLoader.getSystemResource("images/3icon.png"));
        Image i14 = i13.getImage().getScaledInstance(10, 25, Image.SCALE_DEFAULT);
        ImageIcon i15 = new ImageIcon(i14);
        JLabel morevert = new JLabel(i15);
        morevert.setBounds(420, 20, 10, 25);
        p1.add(morevert);
        
        JLabel name = new JLabel("Me");
        name.setBounds(110, 15, 100, 18);
        name.setForeground(Color.WHITE);
        name.setFont(new Font("SAN_SERIF", Font.BOLD, 18));
        p1.add(name);
        
        JLabel status = new JLabel("Active");
        status.setBounds(110, 35, 100, 18);
        status.setForeground(Color.WHITE);
        status.setFont(new Font("SAN_SERIF", Font.BOLD, 14));
        p1.add(status);
        
        a1 = new JPanel();
        a1.setBounds(5, 75, 440, 500);
        f.add(a1);
        
        text = new JTextField();
        text.setBounds(5, 575, 310, 40);
        text.setFont(new Font("SAN_SERIF", Font.PLAIN, 16));
        f.add(text);
        
        JButton send = new JButton("Send");
        send.setBounds(320, 575, 123, 40);
        send.setBackground(new Color(37, 147, 211));
        send.setForeground(Color.WHITE);
        send.addActionListener(this);
        send.setFont(new Font("SAN_SERIF", Font.PLAIN, 16));
        f.add(send);
        
        f.setSize(450, 700);
        f.setLocation(800, 50);
        f.setUndecorated(true);
        f.getContentPane().setBackground(Color.WHITE);
        
        f.setVisible(true);
    }
}

Server Java Code

package chatapp;

import java.io.*;
import java.util.*;
import java.text.*;
import java.net.*;
import javax.swing.*;
import java.awt.*;
import javax.swing.border.*;
import java.awt.event.*;

public class Server implements ActionListener {
    
    JTextField text;
    JPanel a1;
    static Box vertical = Box.createVerticalBox();
    static JFrame f = new JFrame();
    static DataOutputStream dout;
    
    public void actionPerformed(ActionEvent ae) {
        try {
            String out = text.getText();
            JPanel p2 = formatLabel(out);
            a1.setLayout(new BorderLayout());
            JPanel right = new JPanel(new BorderLayout());
            right.add(p2, BorderLayout.LINE_END);
            vertical.add(right);
            vertical.add(Box.createVerticalStrut(15));
            a1.add(vertical, BorderLayout.PAGE_START);
            dout.writeUTF(out);
            text.setText("");
            f.repaint();
            f.invalidate();
            f.validate();   
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public static JPanel formatLabel(String out) {
        JPanel panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        JLabel output = new JLabel("<html><p style=\"width: 150px\">" + out + "</p></html>");
        output.setFont(new Font("Tahoma", Font.PLAIN, 16));
        output.setBackground(new Color(37, 211, 102));
        output.setOpaque(true);
        output.setBorder(new EmptyBorder(15, 15, 15, 50));
        panel.add(output);
        Calendar cal = Calendar.getInstance();
        SimpleDateFormat sdf = new SimpleDateFormat("HH:mm");
        JLabel time = new JLabel();
        time.setText(sdf.format(cal.getTime()));
        panel.add(time);
        return panel;
    }
    
    public static void main(String[] args) {
        new Server();
        try {
            ServerSocket skt = new ServerSocket(6001);
            while(true) {
                Socket s = skt.accept();
                DataInputStream din = new DataInputStream(s.getInputStream());
                dout = new DataOutputStream(s.getOutputStream());
                while(true) {
                    String msg = din.readUTF();
                    JPanel panel = formatLabel(msg);
                    JPanel left = new JPanel(new BorderLayout());
                    left.add(panel, BorderLayout.LINE_START);
                    vertical.add(left);
                    f.validate();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    Server() {
        f.setLayout(null);
        JPanel p1 = new JPanel();
        p1.setBackground(new Color(37, 147, 211));
        p1.setBounds(0, 0, 450, 70);
        p1.setLayout(null);
        f.add(p1);
        
        ImageIcon i1 = new ImageIcon(ClassLoader.getSystemResource("images/3.png"));
        Image i2 = i1.getImage().getScaledInstance(25, 25, Image.SCALE_DEFAULT);
        ImageIcon i3 = new ImageIcon(i2);
        JLabel back = new JLabel(i3);
        back.setBounds(5, 20, 25, 25);
        p1.add(back);
        
        back.addMouseListener(new MouseAdapter() {
            public void mouseClicked(MouseEvent ae) {
                System.exit(0);
            }
        });
        
        ImageIcon i4 = new ImageIcon(ClassLoader.getSystemResource(""));
        Image i5 = i4.getImage().getScaledInstance(50, 50, Image.SCALE_DEFAULT);
        ImageIcon i6 = new ImageIcon(i5);
        JLabel profile = new JLabel(i6);
        profile.setBounds(40, 10, 50, 50);
        p1.add(profile);
        
        ImageIcon i7 = new ImageIcon(ClassLoader.getSystemResource("images/video.png"));
        Image i8 = i7.getImage().getScaledInstance(30, 30, Image.SCALE_DEFAULT);
        ImageIcon i9 = new ImageIcon(i8);
        JLabel video = new JLabel(i9);
        video.setBounds(300, 20, 30, 30);
        p1.add(video);
        
        ImageIcon i10 = new ImageIcon(ClassLoader.getSystemResource("images/phone.png"));
        Image i11 = i10.getImage().getScaledInstance(35, 30, Image.SCALE_DEFAULT);
        ImageIcon i12 = new ImageIcon(i11);
        JLabel phone = new JLabel(i12);
        phone.setBounds(360, 20, 35, 30);
        p1.add(phone);
        
        ImageIcon i13 = new ImageIcon(ClassLoader.getSystemResource("images/3icon.png"));
        Image i14 = i13.getImage().getScaledInstance(10, 25, Image.SCALE_DEFAULT);
        ImageIcon i15 = new ImageIcon(i14);
        JLabel morevert = new JLabel(i15);
        morevert.setBounds(420, 20, 10, 25);
        p1.add(morevert);
        
        JLabel name = new JLabel("Friend");
        name.setBounds(110, 15, 100, 18);
        name.setForeground(Color.WHITE);
        name.setFont(new Font("SAN_SERIF", Font.BOLD, 18));
        p1.add(name);
        
        JLabel status = new JLabel("Active");
        status.setBounds(110, 35, 100, 18);
        status.setForeground(Color.WHITE);
        status.setFont(new Font("SAN_SERIF", Font.BOLD, 14));
        p1.add(status);
        
        a1 = new JPanel();
        a1.setBounds(5, 75, 440, 500);
        f.add(a1);
        
        text = new JTextField();
        text.setBounds(5, 575, 310, 40);
        text.setFont(new Font("SAN_SERIF", Font.PLAIN, 16));
        f.add(text);
        
        JButton send = new JButton("Send");
        send.setBounds(320, 575, 123, 40);
        send.setBackground(new Color(37, 147, 211));
        send.setForeground(Color.WHITE);
        send.addActionListener(this);
        send.setFont(new Font("SAN_SERIF", Font.PLAIN, 16));
        f.add(send);
        
        f.setSize(450, 700);
        f.setLocation(200, 50);
        f.setUndecorated(true);
        f.getContentPane().setBackground(Color.WHITE);
        
        f.setVisible(true);
    }
}

Conclusion

You’ve now created a basic Java Chat Application that enables message exchange between a client and a server.
To level up, consider implementing features like group messaging, user authentication, typing indicators, and media sharing. Keep experimenting, and turn this simple chat into a full-fledged messaging platform!

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