Java Chat Program Using TCP Socket | Java Networking

Java Chat Program

When we are developing a client/server model based application, first we need to make a decisions that whether the application is to run over TCP or over UDP.

TCP is connection-oriented and provides a reliable byte stream channel through which data flows between two end systems. UDP is connection-less and sends independent packets of data from one end system to the other, without any guarantees about delivery.

Client Side Code

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

public class ClientTCP 
{
    public static void main(String[] args) throws Exception {
        Socket s = new Socket("localhost", 30000);  
        DataInputStream dis = new DataInputStream(s.getInputStream());
        DataOutputStream dos = new DataOutputStream(s.getOutputStream());
        String msg = "";
        Scanner sc = new Scanner(System.in);
        while(true) {
            System.out.print("Client: ");
            msg = sc.nextLine();
            dos.writeUTF(msg);
            if (msg.equals("stop")) {
                break; 
            }
            msg = dis.readUTF();
            System.out.println("Server: " + msg);           
        }
        dis.close();
        dos.close();
        s.close();
    }
}

Server Side Code

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

public class ServerTCP
{
    public static void main(String[] args) throws Exception {
        ServerSocket ss = new ServerSocket(30000);
        Socket s = ss.accept(); 
        System.out.println("connection established...");
        DataInputStream dis = new DataInputStream(s.getInputStream());
        DataOutputStream dos = new DataOutputStream(s.getOutputStream());
        String msg = "";
        Scanner sc = new Scanner(System.in);
        while(true) {
            msg = dis.readUTF();
            System.out.println("Client: " + msg);
            if (msg.equals("stop")) {
                break; 
            }
            System.out.print("Server: ");
            msg = sc.nextLine();
            dos.writeUTF(msg);         
        }
        dis.close();
        dos.close();
        s.close();
        ss.close();
    }
}

Output

Make sure to run the server program first and then the client program.