Java example source code file (TwoStacksPlainDatagramSocketImpl.java)

This example Java source code file (TwoStacksPlainDatagramSocketImpl.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractplaindatagramsocketimpl, boolean, closed, deprecated, filedescriptor, inetaddress, ioexception, networkinterface, object, override, so_bindaddr, so_reuseaddr, socketexception, twostacksplaindatagramsocketimpl

The TwoStacksPlainDatagramSocketImpl.java Java example source code

/*
 * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package java.net;

import java.io.IOException;
import java.io.FileDescriptor;
import sun.net.ResourceManager;

/**
 * This class defines the plain DatagramSocketImpl that is used for all
 * Windows versions lower than Vista. It adds support for IPv6 on
 * these platforms where available.
 *
 * For backward compatibility windows platforms that do not have IPv6
 * support also use this implementation, and fd1 gets set to null
 * during socket creation.
 *
 * @author Chris Hegarty
 */

class TwoStacksPlainDatagramSocketImpl extends AbstractPlainDatagramSocketImpl
{
    /* Used for IPv6 on Windows only */
    private FileDescriptor fd1;

    /*
     * Needed for ipv6 on windows because we need to know
     * if the socket was bound to ::0 or 0.0.0.0, when a caller
     * asks for it. In this case, both sockets are used, but we
     * don't know whether the caller requested ::0 or 0.0.0.0
     * and need to remember it here.
     */
    private InetAddress anyLocalBoundAddr=null;

    private int fduse=-1; /* saved between peek() and receive() calls */

    /* saved between successive calls to receive, if data is detected
     * on both sockets at same time. To ensure that one socket is not
     * starved, they rotate using this field
     */
    private int lastfd=-1;

    static {
        init();
    }

    // true if this socket is exclusively bound
    private final boolean exclusiveBind;

    /*
     * Set to true if SO_REUSEADDR is set after the socket is bound to
     * indicate SO_REUSEADDR is being emulated
     */
    private boolean reuseAddressEmulated;

    // emulates SO_REUSEADDR when exclusiveBind is true and socket is bound
    private boolean isReuseAddress;

    TwoStacksPlainDatagramSocketImpl(boolean exclBind) {
        exclusiveBind = exclBind;
    }

    protected synchronized void create() throws SocketException {
        fd1 = new FileDescriptor();
        try {
            super.create();
        } catch (SocketException e) {
            fd1 = null;
            throw e;
        }
    }

    protected synchronized void bind(int lport, InetAddress laddr)
        throws SocketException {
        super.bind(lport, laddr);
        if (laddr.isAnyLocalAddress()) {
            anyLocalBoundAddr = laddr;
        }
    }

    @Override
    protected synchronized void bind0(int lport, InetAddress laddr)
        throws SocketException
    {
        bind0(lport, laddr, exclusiveBind);

    }

    protected synchronized void receive(DatagramPacket p)
        throws IOException {
        try {
            receive0(p);
        } finally {
            fduse = -1;
        }
    }

    public Object getOption(int optID) throws SocketException {
        if (isClosed()) {
            throw new SocketException("Socket Closed");
        }

        if (optID == SO_BINDADDR) {
            if ((fd != null && fd1 != null) && !connected) {
                return anyLocalBoundAddr;
            }
            int family = connectedAddress == null ? -1 : connectedAddress.holder().getFamily();
            return socketLocalAddress(family);
        } else if (optID == SO_REUSEADDR && reuseAddressEmulated) {
            return isReuseAddress;
        } else {
            return super.getOption(optID);
        }
    }

    protected void socketSetOption(int opt, Object val)
        throws SocketException
    {
        if (opt == SO_REUSEADDR && exclusiveBind && localPort != 0)  {
            // socket already bound, emulate
            reuseAddressEmulated = true;
            isReuseAddress = (Boolean)val;
        } else {
            socketNativeSetOption(opt, val);
        }

    }

    protected boolean isClosed() {
        return (fd == null && fd1 == null) ? true : false;
    }

    protected void close() {
        if (fd != null || fd1 != null) {
            datagramSocketClose();
            ResourceManager.afterUdpClose();
            fd = null;
            fd1 = null;
        }
    }

    /* Native methods */

    protected synchronized native void bind0(int lport, InetAddress laddr,
                                             boolean exclBind)
        throws SocketException;

    protected native void send(DatagramPacket p) throws IOException;

    protected synchronized native int peek(InetAddress i) throws IOException;

    protected synchronized native int peekData(DatagramPacket p) throws IOException;

    protected synchronized native void receive0(DatagramPacket p)
        throws IOException;

    protected native void setTimeToLive(int ttl) throws IOException;

    protected native int getTimeToLive() throws IOException;

    @Deprecated
    protected native void setTTL(byte ttl) throws IOException;

    @Deprecated
    protected native byte getTTL() throws IOException;

    protected native void join(InetAddress inetaddr, NetworkInterface netIf)
        throws IOException;

    protected native void leave(InetAddress inetaddr, NetworkInterface netIf)
        throws IOException;

    protected native void datagramSocketCreate() throws SocketException;

    protected native void datagramSocketClose();

    protected native void socketNativeSetOption(int opt, Object val)
        throws SocketException;

    protected native Object socketGetOption(int opt) throws SocketException;

    protected native void connect0(InetAddress address, int port) throws SocketException;

    protected native Object socketLocalAddress(int family) throws SocketException;

    protected native void disconnect0(int family);

    /**
     * Perform class load-time initializations.
     */
    private native static void init();
}