纯java实现ICMP的ping命令

import java.io.*;
import java.net.*;
import java.nio.channels.*;
import java.util.*;
import java.util.regex.*;
public class Ping {
    static int DAYTIME_PORT = 13;
    static int port = DAYTIME_PORT;
    static class Target {
        InetSocketAddress address;
        SocketChannel channel;
        Exception failure;
        long connectStart;
        long connectFinish = 0;
        boolean shown = false;
        Target(String host) {
            try {
                address = new InetSocketAddress(InetAddress.getByName(host),
                        port);
            } catch (IOException x) {
                failure = x;
            }
        }
        void show() {
            String result;
            if (connectFinish != 0)
                result = Long.toString(connectFinish - connectStart) + "ms";
            else if (failure != null)
                result = failure.toString();
            else
                result = "Timed out";
            System.out.println(address + " : " + result);
            shown = true;
        }
    }
    static class Printer extends Thread {
        LinkedList pending = new LinkedList();
        Printer() {
            setName("Printer");
            setDaemon(true);
        }
        void add(Target t) {
            synchronized (pending) {
                pending.add(t);
                pending.notify();
            }
        }
        public void run() {
            try {
                for (;;) {
                    Target t = null;
                    synchronized (pending) {
                        while (pending.size() == 0)
                            pending.wait();
                        t = (Target) pending.removeFirst();
                    }
                    t.show();
                }
            } catch (InterruptedException x) {
                return;
            }
        }
    }
    static class Connector extends Thread {
        Selector sel;
        Printer printer;
        LinkedList pending = new LinkedList();
        Connector(Printer pr) throws IOException {
            printer = pr;
            sel = Selector.open();
            setName("Connector");
        }
        void add(Target t) {
            SocketChannel sc = null;
            try {
                sc = SocketChannel.open();
                sc.configureBlocking(false);
                boolean connected = sc.connect(t.address);
                t.channel = sc;
                t.connectStart = System.currentTimeMillis();
                if (connected) {
                    t.connectFinish = t.connectStart;
                    sc.close();
                    printer.add(t);
                } else {
                    synchronized (pending) {
                        pending.add(t);
                    }
                    sel.wakeup();
                }
            } catch (IOException x) {
                if (sc != null) {
                    try {
                        sc.close();
                    } catch (IOException xx) {
                    }
                }
                t.failure = x;
                printer.add(t);
            }
        }
        void processPendingTargets() throws IOException {
            synchronized (pending) {
                while (pending.size() > 0) {
                    Target t = (Target) pending.removeFirst();
                    try {
                        t.channel.register(sel, SelectionKey.OP_CONNECT, t);
                    } catch (IOException x) {
                        t.channel.close();
                        t.failure = x;
                        printer.add(t);
                    }
                }
            }
        }
        void processSelectedKeys() throws IOException {
            for (Iterator i = sel.selectedKeys().iterator(); i.hasNext();) {
                SelectionKey sk = (SelectionKey) i.next();
                i.remove();
                Target t = (Target) sk.attachment();
                SocketChannel sc = (SocketChannel) sk.channel();
                try {
                    if (sc.finishConnect()) {
                        sk.cancel();
                        t.connectFinish = System.currentTimeMillis();
                        sc.close();
                        printer.add(t);
                    }
                } catch (IOException x) {
                    sc.close();
                    t.failure = x;
                    printer.add(t);
                }
            }
        }
        volatile boolean shutdown = false;
        void shutdown() {
            shutdown = true;
            sel.wakeup();
        }
        public void run() {
            for (;;) {
                try {
                    int n = sel.select();
                    if (n > 0)
                        processSelectedKeys();
                    processPendingTargets();
                    if (shutdown) {
                        sel.close();
                        return;
                    }
                } catch (IOException x) {
                    x.printStackTrace();
                }
            }
        }
    }
    public static void main(String[] args) throws InterruptedException,
            IOException {
        args = new String[] { "8888", "192.168.10.193" };
        if (args.length < 1) {
            System.err.println("Usage: java Ping [port] host...");
            return;
        }
        int firstArg = 0;
        if (Pattern.matches("[0-9]+", args[0])) {
            port = Integer.parseInt(args[0]);
            firstArg = 1;
        }
        Printer printer = new Printer();
        printer.start();
        Connector connector = new Connector(printer);
        connector.start();
        LinkedList targets = new LinkedList();
        for (int i = firstArg; i < args.length; i++) {
            Target t = new Target(args[i]);
            targets.add(t);
            connector.add(t);
        }
        Thread.sleep(2000);
        connector.shutdown();
        connector.join();
        for (Iterator i = targets.iterator(); i.hasNext();) {
            Target t = (Target) i.next();
            if (!t.shown)
                t.show();
        }
    }
}