PortScanner

import java.net.*;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;

// Multithreaded port scanner
public class PortScanner {

    private int start_port, end_port; // range of ports to scan
    private int timeout = 0; // timeout for the probe
    private String host_name; // host name
    private InetAddress host_address; // host address
    private ExecutorService thread_pool; // thread pool

    // Constructor
    public PortScanner (int start_port, int end_port, String host_name) throws PortException, HostException {
        // checking ports
        if (start_port < 0 || end_port < 0 || start_port > end_port || end_port > 65535)
            throw new PortException("Ports must be integers greater than zero and start port must be lower than end port");
        // checking address
        try {
            host_address = InetAddress.getByName(host_name);
        } catch (UnknownHostException e) {
            throw new HostException("Host unreachable");
        }
        // setting properties
        this.setHostName(host_name);
        this.setStartPort(start_port);
        this.setEndPort(end_port);
        // creating thread pool
        thread_pool = Executors.newFixedThreadPool(100);
    }

    // Getters and setters
    public int getStartPort () { return start_port;}
    public int getEndPort () { return end_port;}
    public int getTimeout() { return timeout; }
    public String getHostName () { return host_name;}
    public void setStartPort (int v) { start_port = v; }
    public void setEndPort (int v) { end_port = v; }
    public void setTimeout (int v) { timeout = v; }
    public void setHostName (String v) { host_name = v; }

    // Starts the PortScanner
    public void startScan() throws PortException {
        int pt = getStartPort(), ep = getEndPort();
        while (pt <= ep) {
            thread_pool.execute(new Probe(host_address, pt, timeout));
            pt ++;
        }
        thread_pool.shutdown(); // shut down the pool
    }

    // Terminates the PortScanner
    public void stopScan() {
        // forcing termination
        thread_pool.shutdownNow();
    }
}