Java実装ping

一、純Java実装ICMPのpingコマンド

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();
		}
	}
}

 
二、JAVAが外部EXEを呼び出してPING機能を実現する

import java.io.*;
import java.lang.*;

public class Ping {
	public Ping() {
	}

	public static void main(String args[]) {
		if (args.length < 1) {
			System.out.println("syntax Error!");
		} else {
			String line = null;
			try {
				Process pro = Runtime.getRuntime().exec("ping " + args[0]);
				BufferedReader buf = new BufferedReader(new InputStreamReader(
						pro.getInputStream()));
				while ((line = buf.readLine()) != null)
					System.out.println(line);
			} catch (Exception ex) {
				System.out.println(ex.getMessage());
			}
		}
	}
}

 
三、ICMP Ping in Java(JDK 1.5 and above)

Programatically using ICMP Ping is a great way to establish that a server is up and running. Previously you couldn't do ICMP ping (what ping command does in Linux/Unix & Windows) in java without using JNI or exec calls. Here is a simple and reliable method to do ICMP pings in Java without using JNI or NIO.

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class Ping {
	public static void main(String args[]) {
		try {
			String host = "127.0.0.1";
			int timeOut = 1000; // I recommend 3 seconds at least
			boolean status = InetAddress.getByName(host).isReachable(timeOut);
			System.out.println(status);
		} catch (UnknownHostException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

status is true if the machine is reachable by ping; false otherwise. Best effort is made to try to reach the host, but firewalls and server configuration may block requests resulting in a unreachable status while some specific ports may be accessible. A typical implementation will use ICMP ECHO REQUESTs if the privilege can be obtained, otherwise it will try to establish a TCP connection on port 7 (Echo) of the destination host.
In Linux/Unix you may have to suid the java executable to get ICMP Ping working, ECHO REQUESTs will be fine even without suid. However on Windows you can get ICMP Ping without any issues whatsoever.
 

四、最も簡単な方法、直接CMDを呼び出す

import java.io.*;

public class Ping {
	public static void main(String args[]) {
		String line = null;
		try {
			Process pro = Runtime.getRuntime().exec("ping 127.0.0.1 ");
			BufferedReader buf = new BufferedReader(new InputStreamReader(pro
					.getInputStream()));
			while ((line = buf.readLine()) != null)
				System.out.println(line);
		} catch (Exception ex) {
			System.out.println(ex.getMessage());
		}
	}
}

 
五、アナログPING

InetAddressのisReachableメソッドでpingの機能を実現し、パラメータにタイムアウト時間を設定し、結果を返して接続するかどうかを示す

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class Ping {
	public static void main(String args[]) {
		try {
			InetAddress address = InetAddress.getByName("127.0.0.1");
			System.out.println(address.isReachable(5000));
		} catch (UnknownHostException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

 
六、模擬TELNET

Socketのconnect(SocketAddress endpoint,int timeout)メソッドを使用してtelnetの機能を実現できます.catchが異常説明telnetに失敗した場合

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.UnknownHostException;

public class Ping {
	public static void main(String args[]) {
		try {
			Socket server = new Socket();
			InetSocketAddress address = new InetSocketAddress("127.0.0.1",80);
			server.connect(address, 5000);
			server.close();
			System.out.println("telnet ok");
		} catch (UnknownHostException e) {
			System.out.println("telnet  ");
		} catch (IOException e) {
			System.out.println("telnet  ");
		}

	}
}