/* * Copyright (c) 1996, 2006, 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; /** * 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</code> 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, java.lang.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.     * <P>     * @see Socket#setTcpNoDelay     * @see Socket#getTcpNoDelay     */     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     * <P>     * @see Socket#getLocalAddress     * @see DatagramSocket#getLocalAddress     */     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     */     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     */     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     * <P>     * @see MulticastSocket#setInterface(InetAddress)     * @see MulticastSocket#getInterface()     */     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     */    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     */     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     */     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     */    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     */    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     */    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     */    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     */    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     */    public final static int SO_OOBINLINE = 0x1003;}