NetworkScanner.java

import java.util.Scanner;
import java.net.Socket;
import java.net.InetSocketAddress;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;


public class NetworkScanner {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.print("Enter target IP: ");
        String host = input.nextLine();

        System.out.print("Enter start port: ");
        int startPort = input.nextInt();

        System.out.print("Enter end port: ");
        int endPort = input.nextInt();
        // String host = "127.0.0.1"; // target IP
        // int startPort = 1;
        // int endPort = 1024;

        System.out.println("Scanning host: " + host);

       for (int port = startPort; port <= endPort; port++) {
            final int currentPort = port;

            new Thread(() -> {
                scanPort(host, currentPort);
            }).start();
        }
        try {
                Thread.sleep(5);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    }
    public static String getServiceName(int port) {
    switch (port) {
        case 21: return "FTP";
        case 22: return "SSH";
        case 23: return "TELNET";
        case 25: return "SMTP";
        case 53: return "DNS";
        case 80: return "HTTP";
        case 110: return "POP3";
        case 143: return "IMAP";
        case 443: return "HTTPS";
        default: return "Unknown";
    }
}
    public static void scanPort(String host, int port) {
        try {
        Socket socket = new Socket();
        socket.connect(new InetSocketAddress(host, port), 500);

        System.out.println("Port " + port + " (" + getServiceName(port) + ") is OPEN");

        // Banner grabbing
        socket.setSoTimeout(500);
        try {
            BufferedReader reader = new BufferedReader(
                new InputStreamReader(socket.getInputStream())
            );

            // For HTTP, send request
            if (port == 80 || port == 8080) {
                PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
                writer.println("HEAD / HTTP/1.1");
                writer.println("Host: " + host);
                writer.println();
            }

            String line = reader.readLine();
            if (line != null) {
                System.out.println("   Banner: " + line);
            }

        } catch (Exception e) {
            // No banner available
        }

        socket.close();

    } catch (IOException e) {
        // closed
    }
    }
    
}