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   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   * 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
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  package java.net;
  
  import java.lang.annotation.Native;
  
  /**
   * Interface of methods to get/set socket options.  This interface is
   * implemented by: <B>SocketImpl</B> and  <B>DatagramSocketImpl</B>.
   * Subclasses of these should override the methods
   * of this interface in order to support their own options.
   * <P>
   * The methods and constants which specify options in this interface are
   * for implementation only.  If you're not subclassing SocketImpl or
   * DatagramSocketImpl, <B>you won't use these directly.</B> There are
   * type-safe methods to get/set each of these options in Socket, ServerSocket,
   * DatagramSocket and MulticastSocket.
   * <P>
   * @author David Brown
   */
  
  
  public interface SocketOptions {
  
      /**
       * Enable/disable the option specified by <I>optID</I>.  If the option
       * is to be enabled, and it takes an option-specific "value",  this is
       * passed in <I>value</I>.  The actual type of value is option-specific,
       * and it is an error to pass something that isn't of the expected type:
       * <BR><PRE>
       * SocketImpl s;
       * ...
       * s.setOption(SO_LINGER, new Integer(10));
       *    // OK - set SO_LINGER w/ timeout of 10 sec.
       * s.setOption(SO_LINGER, new Double(10));
       *    // ERROR - expects java.lang.Integer
       *</PRE>
       * If the requested option is binary, it can be set using this method by
       * a java.lang.Boolean:
       * <BR><PRE>
       * s.setOption(TCP_NODELAY, new Boolean(true));
       *    // OK - enables TCP_NODELAY, a binary option
       * </PRE>
       * <BR>
       * Any option can be disabled using this method with a Boolean(false):
       * <BR><PRE>
       * s.setOption(TCP_NODELAY, new Boolean(false));
       *    // OK - disables TCP_NODELAY
       * s.setOption(SO_LINGER, new Boolean(false));
       *    // OK - disables SO_LINGER
       * </PRE>
       * <BR>
       * For an option that has a notion of on and off, and requires
       * a non-boolean parameter, setting its value to anything other than
       * <I>Boolean(false)</I> implicitly enables it.
       * <BR>
       * Throws SocketException if the option is unrecognized,
       * the socket is closed, or some low-level error occurred
       * <BR>
       * @param optID identifies the option
       * @param value the parameter of the socket option
       * @throws SocketException if the option is unrecognized,
       * the socket is closed, or some low-level error occurred
       * @see #getOption(int)
       */
      public void
          setOption(int optID, Object value) throws SocketException;
  
      /**
       * Fetch the value of an option.
       * Binary options will return java.lang.Boolean(true)
       * if enabled, java.lang.Boolean(false) if disabled, e.g.:
       * <BR><PRE>
       * SocketImpl s;
       * ...
       * Boolean noDelay = (Boolean)(s.getOption(TCP_NODELAY));
       * if (noDelay.booleanValue()) {
       *     // true if TCP_NODELAY is enabled...
       * ...
       * }
       * </PRE>
       * <P>
       * For options that take a particular type as a parameter,
       * getOption(int) will return the parameter's value, else
       * it will return java.lang.Boolean(false):
       * <PRE>
       * Object o = s.getOption(SO_LINGER);
       * if (o instanceof Integer) {
       *     System.out.print("Linger time is " + ((Integer)o).intValue());
       * } else {
       *   // the true type of o is java.lang.Boolean(false);
       * }
       * </PRE>
       *
       * @param optID an {@code int} identifying the option to fetch
       * @return the value of the option
       * @throws SocketException if the socket is closed
       * @throws SocketException if <I>optID</I> is unknown along the
       *         protocol stack (including the SocketImpl)
       * @see #setOption(int, Object)
       */
      public Object getOption(int optID) throws SocketException;
  
      /**
       * The java-supported BSD-style options.
       */
  
      /**
       * Disable Nagle's algorithm for this connection.  Written data
       * to the network is not buffered pending acknowledgement of
       * previously written data.
       *<P>
       * Valid for TCP only: SocketImpl.
       *
       * @see Socket#setTcpNoDelay
       * @see Socket#getTcpNoDelay
       */
  
      @Native public final static int TCP_NODELAY = 0x0001;
  
      /**
       * Fetch the local address binding of a socket (this option cannot
       * be "set" only "gotten", since sockets are bound at creation time,
       * and so the locally bound address cannot be changed).  The default local
       * address of a socket is INADDR_ANY, meaning any local address on a
       * multi-homed host.  A multi-homed host can use this option to accept
       * connections to only one of its addresses (in the case of a
       * ServerSocket or DatagramSocket), or to specify its return address
       * to the peer (for a Socket or DatagramSocket).  The parameter of
       * this option is an InetAddress.
       * <P>
       * This option <B>must</B> be specified in the constructor.
       * <P>
       * Valid for: SocketImpl, DatagramSocketImpl
       *
       * @see Socket#getLocalAddress
       * @see DatagramSocket#getLocalAddress
       */
  
      @Native public final static int SO_BINDADDR = 0x000F;
  
      /** Sets SO_REUSEADDR for a socket.  This is used only for MulticastSockets
       * in java, and it is set by default for MulticastSockets.
       * <P>
       * Valid for: DatagramSocketImpl
       */
  
      @Native public final static int SO_REUSEADDR = 0x04;
  
      /**
       * Sets SO_BROADCAST for a socket. This option enables and disables
       * the ability of the process to send broadcast messages. It is supported
       * for only datagram sockets and only on networks that support
       * the concept of a broadcast message (e.g. Ethernet, token ring, etc.),
       * and it is set by default for DatagramSockets.
       * @since 1.4
       */
  
      @Native public final static int SO_BROADCAST = 0x0020;
  
      /** Set which outgoing interface on which to send multicast packets.
       * Useful on hosts with multiple network interfaces, where applications
       * want to use other than the system default.  Takes/returns an InetAddress.
       * <P>
       * Valid for Multicast: DatagramSocketImpl
       *
       * @see MulticastSocket#setInterface(InetAddress)
       * @see MulticastSocket#getInterface()
       */
  
      @Native public final static int IP_MULTICAST_IF = 0x10;
  
      /** Same as above. This option is introduced so that the behaviour
       *  with IP_MULTICAST_IF will be kept the same as before, while
       *  this new option can support setting outgoing interfaces with either
       *  IPv4 and IPv6 addresses.
       *
       *  NOTE: make sure there is no conflict with this
       * @see MulticastSocket#setNetworkInterface(NetworkInterface)
       * @see MulticastSocket#getNetworkInterface()
       * @since 1.4
       */
      @Native public final static int IP_MULTICAST_IF2 = 0x1f;
  
      /**
       * This option enables or disables local loopback of multicast datagrams.
       * This option is enabled by default for Multicast Sockets.
       * @since 1.4
       */
  
      @Native public final static int IP_MULTICAST_LOOP = 0x12;
  
      /**
       * This option sets the type-of-service or traffic class field
       * in the IP header for a TCP or UDP socket.
       * @since 1.4
       */
  
      @Native public final static int IP_TOS = 0x3;
  
      /**
       * Specify a linger-on-close timeout.  This option disables/enables
       * immediate return from a <B>close()</B> of a TCP Socket.  Enabling
       * this option with a non-zero Integer <I>timeout</I> means that a
       * <B>close()</B> will block pending the transmission and acknowledgement
       * of all data written to the peer, at which point the socket is closed
       * <I>gracefully</I>.  Upon reaching the linger timeout, the socket is
       * closed <I>forcefully</I>, with a TCP RST. Enabling the option with a
       * timeout of zero does a forceful close immediately. If the specified
       * timeout value exceeds 65,535 it will be reduced to 65,535.
       * <P>
       * Valid only for TCP: SocketImpl
       *
       * @see Socket#setSoLinger
       * @see Socket#getSoLinger
       */
      @Native public final static int SO_LINGER = 0x0080;
  
      /** Set a timeout on blocking Socket operations:
       * <PRE>
       * ServerSocket.accept();
       * SocketInputStream.read();
       * DatagramSocket.receive();
       * </PRE>
       *
       * <P> The option must be set prior to entering a blocking
       * operation to take effect.  If the timeout expires and the
       * operation would continue to block,
       * <B>java.io.InterruptedIOException</B> is raised.  The Socket is
       * not closed in this case.
       *
       * <P> Valid for all sockets: SocketImpl, DatagramSocketImpl
       *
       * @see Socket#setSoTimeout
       * @see ServerSocket#setSoTimeout
       * @see DatagramSocket#setSoTimeout
       */
      @Native public final static int SO_TIMEOUT = 0x1006;
  
      /**
       * Set a hint the size of the underlying buffers used by the
       * platform for outgoing network I/O. When used in set, this is a
       * suggestion to the kernel from the application about the size of
       * buffers to use for the data to be sent over the socket. When
       * used in get, this must return the size of the buffer actually
       * used by the platform when sending out data on this socket.
       *
       * Valid for all sockets: SocketImpl, DatagramSocketImpl
       *
       * @see Socket#setSendBufferSize
       * @see Socket#getSendBufferSize
       * @see DatagramSocket#setSendBufferSize
       * @see DatagramSocket#getSendBufferSize
       */
      @Native public final static int SO_SNDBUF = 0x1001;
  
      /**
       * Set a hint the size of the underlying buffers used by the
       * platform for incoming network I/O. When used in set, this is a
       * suggestion to the kernel from the application about the size of
       * buffers to use for the data to be received over the
       * socket. When used in get, this must return the size of the
       * buffer actually used by the platform when receiving in data on
       * this socket.
       *
       * Valid for all sockets: SocketImpl, DatagramSocketImpl
       *
       * @see Socket#setReceiveBufferSize
       * @see Socket#getReceiveBufferSize
       * @see DatagramSocket#setReceiveBufferSize
       * @see DatagramSocket#getReceiveBufferSize
       */
      @Native public final static int SO_RCVBUF = 0x1002;
  
      /**
       * When the keepalive option is set for a TCP socket and no data
       * has been exchanged across the socket in either direction for
       * 2 hours (NOTE: the actual value is implementation dependent),
       * TCP automatically sends a keepalive probe to the peer. This probe is a
       * TCP segment to which the peer must respond.
       * One of three responses is expected:
       * 1. The peer responds with the expected ACK. The application is not
       *    notified (since everything is OK). TCP will send another probe
       *    following another 2 hours of inactivity.
       * 2. The peer responds with an RST, which tells the local TCP that
       *    the peer host has crashed and rebooted. The socket is closed.
       * 3. There is no response from the peer. The socket is closed.
       *
       * The purpose of this option is to detect if the peer host crashes.
       *
       * Valid only for TCP socket: SocketImpl
       *
       * @see Socket#setKeepAlive
       * @see Socket#getKeepAlive
       */
      @Native public final static int SO_KEEPALIVE = 0x0008;
  
      /**
       * When the OOBINLINE option is set, any TCP urgent data received on
       * the socket will be received through the socket input stream.
       * When the option is disabled (which is the default) urgent data
       * is silently discarded.
       *
       * @see Socket#setOOBInline
       * @see Socket#getOOBInline
       */
      @Native public final static int SO_OOBINLINE = 0x1003;
  }
  