1 /*
   2  * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.net;
  27 
  28 /**
  29  * Defines the <em>standard</em> socket options.
  30  *
  31  * <p> The {@link SocketOption#name name} of each socket option defined by this
  32  * class is its field name.
  33  *
  34  * <p> In this release, the socket options defined here are used by {@link
  35  * java.nio.channels.NetworkChannel network} channels in the {@link
  36  * java.nio.channels channels} package.
  37  *
  38  * @since 1.7
  39  */
  40 
  41 public final class StandardSocketOptions {
  42     private StandardSocketOptions() { }
  43 
  44     // -- SOL_SOCKET --
  45 
  46     /**
  47      * Allow transmission of broadcast datagrams.
  48      *
  49      * <p> The value of this socket option is a {@code Boolean} that represents
  50      * whether the option is enabled or disabled. The option is specific to
  51      * datagram-oriented sockets sending to {@link java.net.Inet4Address IPv4}
  52      * broadcast addresses. When the socket option is enabled then the socket
  53      * can be used to send <em>broadcast datagrams</em>.
  54      *
  55      * <p> The initial value of this socket option is {@code FALSE}. The socket
  56      * option may be enabled or disabled at any time. Some operating systems may
  57      * require that the Java virtual machine be started with implementation
  58      * specific privileges to enable this option or send broadcast datagrams.
  59      *
  60      * @see <a href="http://www.ietf.org/rfc/rfc919.txt">RFC&nbsp;929:
  61      * Broadcasting Internet Datagrams</a>
  62      * @see DatagramSocket#setBroadcast
  63      */
  64     public static final SocketOption<Boolean> SO_BROADCAST =
  65         new StdSocketOption<Boolean>("SO_BROADCAST", Boolean.class);
  66 
  67     /**
  68      * Keep connection alive.
  69      *
  70      * <p> The value of this socket option is a {@code Boolean} that represents
  71      * whether the option is enabled or disabled. When the {@code SO_KEEPALIVE}
  72      * option is enabled the operating system may use a <em>keep-alive</em>
  73      * mechanism to periodically probe the other end of a connection when the
  74      * connection is otherwise idle. The exact semantics of the keep alive
  75      * mechanism is system dependent and therefore unspecified.
  76      *
  77      * <p> The initial value of this socket option is {@code FALSE}. The socket
  78      * option may be enabled or disabled at any time.
  79      *
  80      * @see <a href="http://www.ietf.org/rfc/rfc1122.txt">RFC&nbsp;1122
  81      * Requirements for Internet Hosts -- Communication Layers</a>
  82      * @see Socket#setKeepAlive
  83      */
  84     public static final SocketOption<Boolean> SO_KEEPALIVE =
  85         new StdSocketOption<Boolean>("SO_KEEPALIVE", Boolean.class);
  86 
  87     /**
  88      * The size of the socket send buffer.
  89      *
  90      * <p> The value of this socket option is an {@code Integer} that is the
  91      * size of the socket send buffer in bytes. The socket send buffer is an
  92      * output buffer used by the networking implementation. It may need to be
  93      * increased for high-volume connections. The value of the socket option is
  94      * a <em>hint</em> to the implementation to size the buffer and the actual
  95      * size may differ. The socket option can be queried to retrieve the actual
  96      * size.
  97      *
  98      * <p> For datagram-oriented sockets, the size of the send buffer may limit
  99      * the size of the datagrams that may be sent by the socket. Whether
 100      * datagrams larger than the buffer size are sent or discarded is system
 101      * dependent.
 102      *
 103      * <p> The initial/default size of the socket send buffer and the range of
 104      * allowable values is system dependent although a negative size is not
 105      * allowed. An attempt to set the socket send buffer to larger than its
 106      * maximum size causes it to be set to its maximum size.
 107      *
 108      * <p> An implementation allows this socket option to be set before the
 109      * socket is bound or connected. Whether an implementation allows the
 110      * socket send buffer to be changed after the socket is bound is system
 111      * dependent.
 112      *
 113      * @see Socket#setSendBufferSize
 114      */
 115     public static final SocketOption<Integer> SO_SNDBUF =
 116         new StdSocketOption<Integer>("SO_SNDBUF", Integer.class);
 117 
 118 
 119     /**
 120      * The size of the socket receive buffer.
 121      *
 122      * <p> The value of this socket option is an {@code Integer} that is the
 123      * size of the socket receive buffer in bytes. The socket receive buffer is
 124      * an input buffer used by the networking implementation. It may need to be
 125      * increased for high-volume connections or decreased to limit the possible
 126      * backlog of incoming data. The value of the socket option is a
 127      * <em>hint</em> to the implementation to size the buffer and the actual
 128      * size may differ.
 129      *
 130      * <p> For datagram-oriented sockets, the size of the receive buffer may
 131      * limit the size of the datagrams that can be received. Whether datagrams
 132      * larger than the buffer size can be received is system dependent.
 133      * Increasing the socket receive buffer may be important for cases where
 134      * datagrams arrive in bursts faster than they can be processed.
 135      *
 136      * <p> In the case of stream-oriented sockets and the TCP/IP protocol, the
 137      * size of the socket receive buffer may be used when advertising the size
 138      * of the TCP receive window to the remote peer.
 139      *
 140      * <p> The initial/default size of the socket receive buffer and the range
 141      * of allowable values is system dependent although a negative size is not
 142      * allowed. An attempt to set the socket receive buffer to larger than its
 143      * maximum size causes it to be set to its maximum size.
 144      *
 145      * <p> An implementation allows this socket option to be set before the
 146      * socket is bound or connected. Whether an implementation allows the
 147      * socket receive buffer to be changed after the socket is bound is system
 148      * dependent.
 149      *
 150      * @see <a href="http://www.ietf.org/rfc/rfc1323.txt">RFC&nbsp;1323: TCP
 151      * Extensions for High Performance</a>
 152      * @see Socket#setReceiveBufferSize
 153      * @see ServerSocket#setReceiveBufferSize
 154      */
 155     public static final SocketOption<Integer> SO_RCVBUF =
 156         new StdSocketOption<Integer>("SO_RCVBUF", Integer.class);
 157 
 158     /**
 159      * Re-use address.
 160      *
 161      * <p> The value of this socket option is a {@code Boolean} that represents
 162      * whether the option is enabled or disabled. The exact semantics of this
 163      * socket option are socket type and system dependent.
 164      *
 165      * <p> In the case of stream-oriented sockets, this socket option will
 166      * usually determine whether the socket can be bound to a socket address
 167      * when a previous connection involving that socket address is in the
 168      * <em>TIME_WAIT</em> state. On implementations where the semantics differ,
 169      * and the socket option is not required to be enabled in order to bind the
 170      * socket when a previous connection is in this state, then the
 171      * implementation may choose to ignore this option.
 172      *
 173      * <p> For datagram-oriented sockets the socket option is used to allow
 174      * multiple programs bind to the same address. This option should be enabled
 175      * when the socket is to be used for Internet Protocol (IP) multicasting.
 176      *
 177      * <p> An implementation allows this socket option to be set before the
 178      * socket is bound or connected. Changing the value of this socket option
 179      * after the socket is bound has no effect. The default value of this
 180      * socket option is system dependent.
 181      *
 182      * @see <a href="http://www.ietf.org/rfc/rfc793.txt">RFC&nbsp;793: Transmission
 183      * Control Protocol</a>
 184      * @see ServerSocket#setReuseAddress
 185      */
 186     public static final SocketOption<Boolean> SO_REUSEADDR =
 187         new StdSocketOption<Boolean>("SO_REUSEADDR", Boolean.class);
 188 
 189     /**
 190      * Linger on close if data is present.
 191      *
 192      * <p> The value of this socket option is an {@code Integer} that controls
 193      * the action taken when unsent data is queued on the socket and a method
 194      * to close the socket is invoked. If the value of the socket option is zero
 195      * or greater, then it represents a timeout value, in seconds, known as the
 196      * <em>linger interval</em>. The linger interval is the timeout for the
 197      * {@code close} method to block while the operating system attempts to
 198      * transmit the unsent data or it decides that it is unable to transmit the
 199      * data. If the value of the socket option is less than zero then the option
 200      * is disabled. In that case the {@code close} method does not wait until
 201      * unsent data is transmitted; if possible the operating system will transmit
 202      * any unsent data before the connection is closed.
 203      *
 204      * <p> This socket option is intended for use with sockets that are configured
 205      * in {@link java.nio.channels.SelectableChannel#isBlocking() blocking} mode
 206      * only. The behavior of the {@code close} method when this option is
 207      * enabled on a non-blocking socket is not defined.
 208      *
 209      * <p> The initial value of this socket option is a negative value, meaning
 210      * that the option is disabled. The option may be enabled, or the linger
 211      * interval changed, at any time. The maximum value of the linger interval
 212      * is system dependent. Setting the linger interval to a value that is
 213      * greater than its maximum value causes the linger interval to be set to
 214      * its maximum value.
 215      *
 216      * @see Socket#setSoLinger
 217      */
 218     public static final SocketOption<Integer> SO_LINGER =
 219         new StdSocketOption<Integer>("SO_LINGER", Integer.class);
 220 
 221 
 222     // -- IPPROTO_IP --
 223 
 224     /**
 225      * The Type of Service (ToS) octet in the Internet Protocol (IP) header.
 226      *
 227      * <p> The value of this socket option is an {@code Integer} representing
 228      * the value of the ToS octet in IP packets sent by sockets to an {@link
 229      * StandardProtocolFamily#INET IPv4} socket. The interpretation of the ToS
 230      * octet is network specific and is not defined by this class. Further
 231      * information on the ToS octet can be found in <a
 232      * href="http://www.ietf.org/rfc/rfc1349.txt">RFC&nbsp;1349</a> and <a
 233      * href="http://www.ietf.org/rfc/rfc2474.txt">RFC&nbsp;2474</a>. The value
 234      * of the socket option is a <em>hint</em>. An implementation may ignore the
 235      * value, or ignore specific values.
 236      *
 237      * <p> The initial/default value of the TOS field in the ToS octet is
 238      * implementation specific but will typically be {@code 0}. For
 239      * datagram-oriented sockets the option may be configured at any time after
 240      * the socket has been bound. The new value of the octet is used when sending
 241      * subsequent datagrams. It is system dependent whether this option can be
 242      * queried or changed prior to binding the socket.
 243      *
 244      * <p> The behavior of this socket option on a stream-oriented socket, or an
 245      * {@link StandardProtocolFamily#INET6 IPv6} socket, is not defined in this
 246      * release.
 247      *
 248      * @see DatagramSocket#setTrafficClass
 249      */
 250     public static final SocketOption<Integer> IP_TOS =
 251         new StdSocketOption<Integer>("IP_TOS", Integer.class);
 252 
 253     /**
 254      * The network interface for Internet Protocol (IP) multicast datagrams.
 255      *
 256      * <p> The value of this socket option is a {@link NetworkInterface} that
 257      * represents the outgoing interface for multicast datagrams sent by the
 258      * datagram-oriented socket. For {@link StandardProtocolFamily#INET6 IPv6}
 259      * sockets then it is system dependent whether setting this option also
 260      * sets the outgoing interface for multlicast datagrams sent to IPv4
 261      * addresses.
 262      *
 263      * <p> The initial/default value of this socket option may be {@code null}
 264      * to indicate that outgoing interface will be selected by the operating
 265      * system, typically based on the network routing tables. An implementation
 266      * allows this socket option to be set after the socket is bound. Whether
 267      * the socket option can be queried or changed prior to binding the socket
 268      * is system dependent.
 269      *
 270      * @see java.nio.channels.MulticastChannel
 271      * @see MulticastSocket#setInterface
 272      */
 273     public static final SocketOption<NetworkInterface> IP_MULTICAST_IF =
 274         new StdSocketOption<NetworkInterface>("IP_MULTICAST_IF", NetworkInterface.class);
 275 
 276     /**
 277      * The <em>time-to-live</em> for Internet Protocol (IP) multicast datagrams.
 278      *
 279      * <p> The value of this socket option is an {@code Integer} in the range
 280      * <tt>0&nbsp;<=&nbsp;value&nbsp;<=&nbsp;255</tt>. It is used to control
 281      * the scope of multicast datagrams sent by the datagram-oriented socket.
 282      * In the case of an {@link StandardProtocolFamily#INET IPv4} socket
 283      * the option is the time-to-live (TTL) on multicast datagrams sent by the
 284      * socket. Datagrams with a TTL of zero are not transmitted on the network
 285      * but may be delivered locally. In the case of an {@link
 286      * StandardProtocolFamily#INET6 IPv6} socket the option is the
 287      * <em>hop limit</em> which is number of <em>hops</em> that the datagram can
 288      * pass through before expiring on the network. For IPv6 sockets it is
 289      * system dependent whether the option also sets the <em>time-to-live</em>
 290      * on multicast datagrams sent to IPv4 addresses.
 291      *
 292      * <p> The initial/default value of the time-to-live setting is typically
 293      * {@code 1}. An implementation allows this socket option to be set after
 294      * the socket is bound. Whether the socket option can be queried or changed
 295      * prior to binding the socket is system dependent.
 296      *
 297      * @see java.nio.channels.MulticastChannel
 298      * @see MulticastSocket#setTimeToLive
 299      */
 300     public static final SocketOption<Integer> IP_MULTICAST_TTL =
 301         new StdSocketOption<Integer>("IP_MULTICAST_TTL", Integer.class);
 302 
 303     /**
 304      * Loopback for Internet Protocol (IP) multicast datagrams.
 305      *
 306      * <p> The value of this socket option is a {@code Boolean} that controls
 307      * the <em>loopback</em> of multicast datagrams. The value of the socket
 308      * option represents if the option is enabled or disabled.
 309      *
 310      * <p> The exact semantics of this socket options are system dependent.
 311      * In particular, it is system dependent whether the loopback applies to
 312      * multicast datagrams sent from the socket or received by the socket.
 313      * For {@link StandardProtocolFamily#INET6 IPv6} sockets then it is
 314      * system dependent whether the option also applies to multicast datagrams
 315      * sent to IPv4 addresses.
 316      *
 317      * <p> The initial/default value of this socket option is {@code TRUE}. An
 318      * implementation allows this socket option to be set after the socket is
 319      * bound. Whether the socket option can be queried or changed prior to
 320      * binding the socket is system dependent.
 321      *
 322      * @see java.nio.channels.MulticastChannel
 323      *  @see MulticastSocket#setLoopbackMode
 324      */
 325     public static final SocketOption<Boolean> IP_MULTICAST_LOOP =
 326         new StdSocketOption<Boolean>("IP_MULTICAST_LOOP", Boolean.class);
 327 
 328 
 329     // -- IPPROTO_TCP --
 330 
 331     /**
 332      * Disable the Nagle algorithm.
 333      *
 334      * <p> The value of this socket option is a {@code Boolean} that represents
 335      * whether the option is enabled or disabled. The socket option is specific to
 336      * stream-oriented sockets using the TCP/IP protocol. TCP/IP uses an algorithm
 337      * known as <em>The Nagle Algorithm</em> to coalesce short segments and
 338      * improve network efficiency.
 339      *
 340      * <p> The default value of this socket option is {@code FALSE}. The
 341      * socket option should only be enabled in cases where it is known that the
 342      * coalescing impacts performance. The socket option may be enabled at any
 343      * time. In other words, the Nagle Algorithm can be disabled. Once the option
 344      * is enabled, it is system dependent whether it can be subsequently
 345      * disabled. If it cannot, then invoking the {@code setOption} method to
 346      * disable the option has no effect.
 347      *
 348      * @see <a href="http://www.ietf.org/rfc/rfc1122.txt">RFC&nbsp;1122:
 349      * Requirements for Internet Hosts -- Communication Layers</a>
 350      * @see Socket#setTcpNoDelay
 351      */
 352     public static final SocketOption<Boolean> TCP_NODELAY =
 353         new StdSocketOption<Boolean>("TCP_NODELAY", Boolean.class);
 354 
 355 
 356     private static class StdSocketOption<T> implements SocketOption<T> {
 357         private final String name;
 358         private final Class<T> type;
 359         StdSocketOption(String name, Class<T> type) {
 360             this.name = name;
 361             this.type = type;
 362         }
 363         @Override public String name() { return name; }
 364         @Override public Class<T> type() { return type; }
 365         @Override public String toString() { return name; }
 366     }
 367 }