1 /*

     2  * Copyright (c) 2007, 2009, 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 StandardSocketOption {

    42     private StandardSocketOption() { }

    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 }