java 实现 ping

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package ping;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[] { "9100", "172.16.2.222" };        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();        }    }}
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