TelnetUtils

TelnetUtils.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

/**
 * @author <a href="mailto:[email protected]">Vegard Aasen</a>
 * @since 10:40 AM
 */
public final class TelnetUtils {

    private static final String HELLO = "ping";
    private static final int TIMEOUT = 500;
    private static final long WAIT = TimeUnit.SECONDS.toMillis(5);

    public static Map<Integer, Boolean> isAlive(final String hostName, final int[] portRange) {
        if (portRange.length != 2) {
            throw new RuntimeException("Ops. too many port in the portRange. Expected 2, found " + portRange.length);
        }
        final Map<Integer, Boolean> alives = new HashMap<>();
        long lastWait = 0L;
        for (int i = portRange[0]; i < portRange[1]; i++) {
            alives.put(i, isAlive(hostName, i));
            if (lastWait == 0 || System.currentTimeMillis() > lastWait + WAIT) {
                printStatus(i, portRange[1]);
                lastWait = System.currentTimeMillis();
            }
        }
        return alives;
    }

    public static boolean isAlive(final String hostName, final int port) {
        try (final Socket pingSocket = new Socket()) {
            pingSocket.connect(new InetSocketAddress(hostName, port), TIMEOUT);
            pingSocket.setKeepAlive(false);
            final PrintWriter out = new PrintWriter(pingSocket.getOutputStream(), true);
            final BufferedReader in = new BufferedReader(new InputStreamReader(pingSocket.getInputStream()));
            out.println(HELLO);
            in.readLine();
            pingSocket.close();
            System.out.println(String.format("%s <- open", port));
            return true;
        } catch (final IOException e) {
            return false;
        }
    }

    private static void printStatus(final int here, final int there) {
        System.out.println(String.format("%s %% - %s/%s", ((double) here * 100.0 / (double) there), here, there));
    }

}

Supersimple..could've used some kind of executorService or whatever, I just didnt bother 😣