icmpsocket.java

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//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2002-2003 The OpenNMS Group, Inc.  All rights reserved.
// OpenNMS(R) is a derivative work, containing both original code, included code and modified
// code that was published under the GNU General Public License. Copyrights for modified 
// and included code are below.
//
// OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
//
// Modifications:
//
// 2003 Mar 05: Changes to support response times and more platforms.
//
// Original code base Copyright (C) 1999-2001 Oculan Corp.  All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// For more information contact:
//      OpenNMS Licensing       <[e-mail]>
//      http://www.opennms.org/
//      http://www.opennms.com/
//
// Tab Size = 8
//

package org.opennms.protocols.icmp;

import java.io.FileDescriptor;
import java.io.IOException;
import java.net.DatagramPacket;

/**
 * This class provides a bridge between the host operating system so that ICMP
 * messages may be sent and received.
 * 
 * @author <a href="mailto:[e-mail]">Brian Weaver </a>
 * @author <a href="http://www.opennms.org/">OpenNMS </a>
 * 
 */
public final class IcmpSocket {
    /**
     * This instance is used by the native code to save and store file
     * descriptor information about the icmp socket. This needs to be
     * constructed prior to calling the init method, preferable in the
     * constructor.
     */
    private FileDescriptor m_rawFd;

    /**
     * This method is used to open the initial operating system icmp socket. The
     * descriptor for the socket is stored in the member m_rawFd.
     * 
     * @throws java.io.IOException
     *             This is thrown if an error occurs opening the ICMP socket.
     */
    private native void initSocket() throws IOException;

    // Load the requried system library. This
    // should be delayed until the class is actually
    // loaded and used, so normally it should not
    // take unecessary resources from an application that
    // is not going to use ICMP.
    //
    static {
        System.loadLibrary("jicmp");
    }

    /**
     * Constructs a new socket that is able to send and receive ICMP messages.
     * The newly constructed socket will receive all ICMP messages directed at
     * the local machine. The application must be prepared to handle any and
     * discard any non-interesting ICMP messages.
     * 
     * @exception java.io.IOException
     *                This exception is thrown if the socket fails to be opened
     *                correctly.
     */
    public IcmpSocket() throws IOException {
        m_rawFd = new FileDescriptor();
        initSocket();
    }

    /**
     * This method is used to receive the next ICMP datagram from the operating
     * system. The returned datagram packet's address is set to the sending
     * host's address. The port number is always set to Zero, and the buffer is
     * set to the contents of the raw ICMP message.
     * 
     * @exception java.io.IOException
     *                Thrown if an error occurs reading the next ICMP message.
     * 
     */
    public final native DatagramPacket receive() throws IOException;

    /**
     * This method is used to send the passed datagram using the ICMP transport.
     * The destination of the datagram packet is used as the send to destination
     * for the underlying ICMP socket. The port number of the datagram packet is
     * ignored completely.
     * 
     * @exception java.io.IOException
     *                Thrown if an error occurs sending the datagram to the
     *                remote host.
     * @exception java.net.NoRouteToHostException
     *                Thrown if the destination address is a broadcast address.
     */
    public final native void send(DatagramPacket packet) throws IOException;

    /**
     * This method is used to close and release the resources assocated with the
     * instance. The file descriptor is closed at the operating system level and
     * any subsequent calls to this instance should result in exceptions being
     * generated.
     */
    public final native void close();
}