https://openjdk.java.net/ 
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 * Copyright (c) 2007, 2019, 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.
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 * 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).
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 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package java.net;


Defines the standard socket options.

 The name of each socket option defined by this class is its field name. 
 In this release, the socket options defined here are used by network channels in the channels package. 
Since:1.7
/**
 * Defines the <em>standard</em> socket options.
 *
 * <p> The {@link SocketOption#name name} of each socket option defined by this
 * class is its field name.
 *
 * <p> In this release, the socket options defined here are used by {@link
 * java.nio.channels.NetworkChannel network} channels in the {@link
 * java.nio.channels channels} package.
 *
 * @since 1.7
 */

public final class StandardSocketOptions {
    private StandardSocketOptions() { }

    // -- SOL_SOCKET --

    
Allow transmission of broadcast datagrams.

 The value of this socket option is a Boolean that represents whether the option is enabled or disabled. The option is specific to datagram-oriented sockets sending to IPv4 broadcast addresses. When the socket option is enabled then the socket can be used to send broadcast datagrams.

 The initial value of this socket option is FALSE. The socket option may be enabled or disabled at any time. Some operating systems may require that the Java virtual machine be started with implementation specific privileges to enable this option or send broadcast datagrams. 
See Also:
/**
     * Allow transmission of broadcast datagrams.
     *
     * <p> The value of this socket option is a {@code Boolean} that represents
     * whether the option is enabled or disabled. The option is specific to
     * datagram-oriented sockets sending to {@link java.net.Inet4Address IPv4}
     * broadcast addresses. When the socket option is enabled then the socket
     * can be used to send <em>broadcast datagrams</em>.
     *
     * <p> The initial value of this socket option is {@code FALSE}. The socket
     * option may be enabled or disabled at any time. Some operating systems may
     * require that the Java virtual machine be started with implementation
     * specific privileges to enable this option or send broadcast datagrams.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc919.txt">RFC&nbsp;929:
     * Broadcasting Internet Datagrams</a>
     * @see DatagramSocket#setBroadcast
     */
    public static final SocketOption<Boolean> SO_BROADCAST =
        new StdSocketOption<Boolean>("SO_BROADCAST", Boolean.class);

    
Keep connection alive.

 The value of this socket option is a Boolean that represents whether the option is enabled or disabled. When the SO_KEEPALIVE option is enabled the operating system may use a keep-alive
mechanism to periodically probe the other end of a connection when the
connection is otherwise idle. The exact semantics of the keep alive
mechanism is system dependent and therefore unspecified.

 The initial value of this socket option is FALSE. The socket option may be enabled or disabled at any time. 
See Also:
/**
     * Keep connection alive.
     *
     * <p> The value of this socket option is a {@code Boolean} that represents
     * whether the option is enabled or disabled. When the {@code SO_KEEPALIVE}
     * option is enabled the operating system may use a <em>keep-alive</em>
     * mechanism to periodically probe the other end of a connection when the
     * connection is otherwise idle. The exact semantics of the keep alive
     * mechanism is system dependent and therefore unspecified.
     *
     * <p> The initial value of this socket option is {@code FALSE}. The socket
     * option may be enabled or disabled at any time.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc1122.txt">RFC&nbsp;1122
     * Requirements for Internet Hosts -- Communication Layers</a>
     * @see Socket#setKeepAlive
     */
    public static final SocketOption<Boolean> SO_KEEPALIVE =
        new StdSocketOption<Boolean>("SO_KEEPALIVE", Boolean.class);

    
The size of the socket send buffer.

 The value of this socket option is an Integer that is the size of the socket send buffer in bytes. The socket send buffer is an output buffer used by the networking implementation. It may need to be increased for high-volume connections. The value of the socket option is a hint to the implementation to size the buffer and the actual
size may differ. The socket option can be queried to retrieve the actual
size.

 For datagram-oriented sockets, the size of the send buffer may limit
the size of the datagrams that may be sent by the socket. Whether
datagrams larger than the buffer size are sent or discarded is system
dependent.

 The initial/default size of the socket send buffer and the range of
allowable values is system dependent although a negative size is not
allowed. An attempt to set the socket send buffer to larger than its
maximum size causes it to be set to its maximum size.

 An implementation allows this socket option to be set before the
socket is bound or connected. Whether an implementation allows the
socket send buffer to be changed after the socket is bound is system
dependent.

See Also:
/**
     * The size of the socket send buffer.
     *
     * <p> The value of this socket option is an {@code Integer} that is the
     * size of the socket send buffer in bytes. The socket send buffer is an
     * output buffer used by the networking implementation. It may need to be
     * increased for high-volume connections. The value of the socket option is
     * a <em>hint</em> to the implementation to size the buffer and the actual
     * size may differ. The socket option can be queried to retrieve the actual
     * size.
     *
     * <p> For datagram-oriented sockets, the size of the send buffer may limit
     * the size of the datagrams that may be sent by the socket. Whether
     * datagrams larger than the buffer size are sent or discarded is system
     * dependent.
     *
     * <p> The initial/default size of the socket send buffer and the range of
     * allowable values is system dependent although a negative size is not
     * allowed. An attempt to set the socket send buffer to larger than its
     * maximum size causes it to be set to its maximum size.
     *
     * <p> An implementation allows this socket option to be set before the
     * socket is bound or connected. Whether an implementation allows the
     * socket send buffer to be changed after the socket is bound is system
     * dependent.
     *
     * @see Socket#setSendBufferSize
     */
    public static final SocketOption<Integer> SO_SNDBUF =
        new StdSocketOption<Integer>("SO_SNDBUF", Integer.class);


    
The size of the socket receive buffer.

 The value of this socket option is an Integer that is the size of the socket receive buffer in bytes. The socket receive buffer is an input buffer used by the networking implementation. It may need to be increased for high-volume connections or decreased to limit the possible backlog of incoming data. The value of the socket option is a hint to the implementation to size the buffer and the actual
size may differ.

 For datagram-oriented sockets, the size of the receive buffer may
limit the size of the datagrams that can be received. Whether datagrams
larger than the buffer size can be received is system dependent.
Increasing the socket receive buffer may be important for cases where
datagrams arrive in bursts faster than they can be processed.

 In the case of stream-oriented sockets and the TCP/IP protocol, the
size of the socket receive buffer may be used when advertising the size
of the TCP receive window to the remote peer.

 The initial/default size of the socket receive buffer and the range
of allowable values is system dependent although a negative size is not
allowed. An attempt to set the socket receive buffer to larger than its
maximum size causes it to be set to its maximum size.

 An implementation allows this socket option to be set before the
socket is bound or connected. Whether an implementation allows the
socket receive buffer to be changed after the socket is bound is system
dependent.

See Also:
/**
     * The size of the socket receive buffer.
     *
     * <p> The value of this socket option is an {@code Integer} that is the
     * size of the socket receive buffer in bytes. The socket receive buffer is
     * an input buffer used by the networking implementation. It may need to be
     * increased for high-volume connections or decreased to limit the possible
     * backlog of incoming data. The value of the socket option is a
     * <em>hint</em> to the implementation to size the buffer and the actual
     * size may differ.
     *
     * <p> For datagram-oriented sockets, the size of the receive buffer may
     * limit the size of the datagrams that can be received. Whether datagrams
     * larger than the buffer size can be received is system dependent.
     * Increasing the socket receive buffer may be important for cases where
     * datagrams arrive in bursts faster than they can be processed.
     *
     * <p> In the case of stream-oriented sockets and the TCP/IP protocol, the
     * size of the socket receive buffer may be used when advertising the size
     * of the TCP receive window to the remote peer.
     *
     * <p> The initial/default size of the socket receive buffer and the range
     * of allowable values is system dependent although a negative size is not
     * allowed. An attempt to set the socket receive buffer to larger than its
     * maximum size causes it to be set to its maximum size.
     *
     * <p> An implementation allows this socket option to be set before the
     * socket is bound or connected. Whether an implementation allows the
     * socket receive buffer to be changed after the socket is bound is system
     * dependent.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc1323.txt">RFC&nbsp;1323: TCP
     * Extensions for High Performance</a>
     * @see Socket#setReceiveBufferSize
     * @see ServerSocket#setReceiveBufferSize
     */
    public static final SocketOption<Integer> SO_RCVBUF =
        new StdSocketOption<Integer>("SO_RCVBUF", Integer.class);

    
Re-use address.

 The value of this socket option is a Boolean that represents whether the option is enabled or disabled. The exact semantics of this socket option are socket type and system dependent. 
 In the case of stream-oriented sockets, this socket option will
usually determine whether the socket can be bound to a socket address
when a previous connection involving that socket address is in the
TIME_WAIT state. On implementations where the semantics differ,
and the socket option is not required to be enabled in order to bind the
socket when a previous connection is in this state, then the
implementation may choose to ignore this option.

 For datagram-oriented sockets the socket option is used to allow
multiple programs bind to the same address. This option should be enabled
when the socket is to be used for Internet Protocol (IP) multicasting.

 An implementation allows this socket option to be set before the
socket is bound or connected. Changing the value of this socket option
after the socket is bound has no effect. The default value of this
socket option is system dependent.

See Also:
/**
     * Re-use address.
     *
     * <p> The value of this socket option is a {@code Boolean} that represents
     * whether the option is enabled or disabled. The exact semantics of this
     * socket option are socket type and system dependent.
     *
     * <p> In the case of stream-oriented sockets, this socket option will
     * usually determine whether the socket can be bound to a socket address
     * when a previous connection involving that socket address is in the
     * <em>TIME_WAIT</em> state. On implementations where the semantics differ,
     * and the socket option is not required to be enabled in order to bind the
     * socket when a previous connection is in this state, then the
     * implementation may choose to ignore this option.
     *
     * <p> For datagram-oriented sockets the socket option is used to allow
     * multiple programs bind to the same address. This option should be enabled
     * when the socket is to be used for Internet Protocol (IP) multicasting.
     *
     * <p> An implementation allows this socket option to be set before the
     * socket is bound or connected. Changing the value of this socket option
     * after the socket is bound has no effect. The default value of this
     * socket option is system dependent.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc793.txt">RFC&nbsp;793: Transmission
     * Control Protocol</a>
     * @see ServerSocket#setReuseAddress
     */
    public static final SocketOption<Boolean> SO_REUSEADDR =
        new StdSocketOption<Boolean>("SO_REUSEADDR", Boolean.class);

    
Re-use port.

 The value of this socket option is a Boolean that represents whether the option is enabled or disabled. The exact semantics of this socket option are socket type and system dependent. 
 In the case of stream-oriented sockets, this socket option usually allows
multiple listening sockets to be bound to both same address
and same port.

 For datagram-oriented sockets the socket option usually allows
multiple UDP sockets to be bound to the same address and port.

 An implementation allows this socket option to be set before the
socket is bound or connected. Changing the value of this socket option
after the socket is bound has no effect.

Since:9
/**
     * Re-use port.
     *
     * <p> The value of this socket option is a {@code Boolean} that represents
     * whether the option is enabled or disabled. The exact semantics of this
     * socket option are socket type and system dependent.
     *
     * <p> In the case of stream-oriented sockets, this socket option usually allows
     * multiple listening sockets to be bound to both same address
     * and same port.
     *
     * <p> For datagram-oriented sockets the socket option usually allows
     * multiple UDP sockets to be bound to the same address and port.
     *
     * <p> An implementation allows this socket option to be set before the
     * socket is bound or connected. Changing the value of this socket option
     * after the socket is bound has no effect.
     *
     * @since 9
     */
    public static final SocketOption<Boolean> SO_REUSEPORT =
        new StdSocketOption<Boolean>("SO_REUSEPORT", Boolean.class);

    
Linger on close if data is present.

 The value of this socket option is an Integer that controls the action taken when unsent data is queued on the socket and a method to close the socket is invoked. If the value of the socket option is zero or greater, then it represents a timeout value, in seconds, known as the linger interval. The linger interval is the timeout for the close method to block while the operating system attempts to transmit the unsent data or it decides that it is unable to transmit the data. If the value of the socket option is less than zero then the option is disabled. In that case the close method does not wait until unsent data is transmitted; if possible the operating system will transmit any unsent data before the connection is closed. 
 This socket option is intended for use with sockets that are configured in blocking mode only. The behavior of the close method when this option is enabled on a non-blocking socket is not defined. 
 The initial value of this socket option is a negative value, meaning
that the option is disabled. The option may be enabled, or the linger
interval changed, at any time. The maximum value of the linger interval
is system dependent. Setting the linger interval to a value that is
greater than its maximum value causes the linger interval to be set to
its maximum value.

See Also:
/**
     * Linger on close if data is present.
     *
     * <p> The value of this socket option is an {@code Integer} that controls
     * the action taken when unsent data is queued on the socket and a method
     * to close the socket is invoked. If the value of the socket option is zero
     * or greater, then it represents a timeout value, in seconds, known as the
     * <em>linger interval</em>. The linger interval is the timeout for the
     * {@code close} method to block while the operating system attempts to
     * transmit the unsent data or it decides that it is unable to transmit the
     * data. If the value of the socket option is less than zero then the option
     * is disabled. In that case the {@code close} method does not wait until
     * unsent data is transmitted; if possible the operating system will transmit
     * any unsent data before the connection is closed.
     *
     * <p> This socket option is intended for use with sockets that are configured
     * in {@link java.nio.channels.SelectableChannel#isBlocking() blocking} mode
     * only. The behavior of the {@code close} method when this option is
     * enabled on a non-blocking socket is not defined.
     *
     * <p> The initial value of this socket option is a negative value, meaning
     * that the option is disabled. The option may be enabled, or the linger
     * interval changed, at any time. The maximum value of the linger interval
     * is system dependent. Setting the linger interval to a value that is
     * greater than its maximum value causes the linger interval to be set to
     * its maximum value.
     *
     * @see Socket#setSoLinger
     */
    public static final SocketOption<Integer> SO_LINGER =
        new StdSocketOption<Integer>("SO_LINGER", Integer.class);


    // -- IPPROTO_IP --

    
The Type of Service (ToS) octet in the Internet Protocol (IP) header.

 The value of this socket option is an Integer representing the value of the ToS octet in IP packets sent by sockets to an IPv4 socket. The interpretation of the ToS octet is network specific and is not defined by this class. Further information on the ToS octet can be found in RFC 1349 and RFC 2474. The value
of the socket option is a hint. An implementation may ignore the
value, or ignore specific values.

 The initial/default value of the TOS field in the ToS octet is implementation specific but will typically be 0. For datagram-oriented sockets the option may be configured at any time after the socket has been bound. The new value of the octet is used when sending subsequent datagrams. It is system dependent whether this option can be queried or changed prior to binding the socket. 
 The behavior of this socket option on a stream-oriented socket, or an IPv6 socket, is not defined in this release. 
See Also:
/**
     * The Type of Service (ToS) octet in the Internet Protocol (IP) header.
     *
     * <p> The value of this socket option is an {@code Integer} representing
     * the value of the ToS octet in IP packets sent by sockets to an {@link
     * StandardProtocolFamily#INET IPv4} socket. The interpretation of the ToS
     * octet is network specific and is not defined by this class. Further
     * information on the ToS octet can be found in <a
     * href="http://www.ietf.org/rfc/rfc1349.txt">RFC&nbsp;1349</a> and <a
     * href="http://www.ietf.org/rfc/rfc2474.txt">RFC&nbsp;2474</a>. The value
     * of the socket option is a <em>hint</em>. An implementation may ignore the
     * value, or ignore specific values.
     *
     * <p> The initial/default value of the TOS field in the ToS octet is
     * implementation specific but will typically be {@code 0}. For
     * datagram-oriented sockets the option may be configured at any time after
     * the socket has been bound. The new value of the octet is used when sending
     * subsequent datagrams. It is system dependent whether this option can be
     * queried or changed prior to binding the socket.
     *
     * <p> The behavior of this socket option on a stream-oriented socket, or an
     * {@link StandardProtocolFamily#INET6 IPv6} socket, is not defined in this
     * release.
     *
     * @see DatagramSocket#setTrafficClass
     */
    public static final SocketOption<Integer> IP_TOS =
        new StdSocketOption<Integer>("IP_TOS", Integer.class);

    
The network interface for Internet Protocol (IP) multicast datagrams.

 The value of this socket option is a NetworkInterface that represents the outgoing interface for multicast datagrams sent by the datagram-oriented socket. For IPv6 sockets then it is system dependent whether setting this option also sets the outgoing interface for multicast datagrams sent to IPv4 addresses. 
 The initial/default value of this socket option may be null to indicate that outgoing interface will be selected by the operating system, typically based on the network routing tables. An implementation allows this socket option to be set after the socket is bound. Whether the socket option can be queried or changed prior to binding the socket is system dependent. 
See Also:
/**
     * The network interface for Internet Protocol (IP) multicast datagrams.
     *
     * <p> The value of this socket option is a {@link NetworkInterface} that
     * represents the outgoing interface for multicast datagrams sent by the
     * datagram-oriented socket. For {@link StandardProtocolFamily#INET6 IPv6}
     * sockets then it is system dependent whether setting this option also
     * sets the outgoing interface for multicast datagrams sent to IPv4
     * addresses.
     *
     * <p> The initial/default value of this socket option may be {@code null}
     * to indicate that outgoing interface will be selected by the operating
     * system, typically based on the network routing tables. An implementation
     * allows this socket option to be set after the socket is bound. Whether
     * the socket option can be queried or changed prior to binding the socket
     * is system dependent.
     *
     * @see java.nio.channels.MulticastChannel
     */
    public static final SocketOption<NetworkInterface> IP_MULTICAST_IF =
        new StdSocketOption<NetworkInterface>("IP_MULTICAST_IF", NetworkInterface.class);

    
The time-to-live for Internet Protocol (IP) multicast datagrams.

 The value of this socket option is an Integer in the range 0 <= value <= 255. It is used to control the scope of multicast datagrams sent by the datagram-oriented socket. In the case of an IPv4 socket the option is the time-to-live (TTL) on multicast datagrams sent by the socket. Datagrams with a TTL of zero are not transmitted on the network but may be delivered locally. In the case of an IPv6 socket the option is the hop limit which is number of hops that the datagram can
pass through before expiring on the network. For IPv6 sockets it is
system dependent whether the option also sets the time-to-live
on multicast datagrams sent to IPv4 addresses.

 The initial/default value of the time-to-live setting is typically 1. An implementation allows this socket option to be set after the socket is bound. Whether the socket option can be queried or changed prior to binding the socket is system dependent. 
See Also:
/**
     * The <em>time-to-live</em> for Internet Protocol (IP) multicast datagrams.
     *
     * <p> The value of this socket option is an {@code Integer} in the range
     * {@code 0 <= value <= 255}. It is used to control the scope of multicast
     * datagrams sent by the datagram-oriented socket.
     * In the case of an {@link StandardProtocolFamily#INET IPv4} socket
     * the option is the time-to-live (TTL) on multicast datagrams sent by the
     * socket. Datagrams with a TTL of zero are not transmitted on the network
     * but may be delivered locally. In the case of an {@link
     * StandardProtocolFamily#INET6 IPv6} socket the option is the
     * <em>hop limit</em> which is number of <em>hops</em> that the datagram can
     * pass through before expiring on the network. For IPv6 sockets it is
     * system dependent whether the option also sets the <em>time-to-live</em>
     * on multicast datagrams sent to IPv4 addresses.
     *
     * <p> The initial/default value of the time-to-live setting is typically
     * {@code 1}. An implementation allows this socket option to be set after
     * the socket is bound. Whether the socket option can be queried or changed
     * prior to binding the socket is system dependent.
     *
     * @see java.nio.channels.MulticastChannel
     * @see MulticastSocket#setTimeToLive
     */
    public static final SocketOption<Integer> IP_MULTICAST_TTL =
        new StdSocketOption<Integer>("IP_MULTICAST_TTL", Integer.class);

    
Loopback for Internet Protocol (IP) multicast datagrams.

 The value of this socket option is a Boolean that controls the loopback of multicast datagrams. The value of the socket
option represents if the option is enabled or disabled.

 The exact semantics of this socket options are system dependent. In particular, it is system dependent whether the loopback applies to multicast datagrams sent from the socket or received by the socket. For IPv6 sockets then it is system dependent whether the option also applies to multicast datagrams sent to IPv4 addresses. 
 The initial/default value of this socket option is TRUE. An implementation allows this socket option to be set after the socket is bound. Whether the socket option can be queried or changed prior to binding the socket is system dependent. 
See Also:
/**
     * Loopback for Internet Protocol (IP) multicast datagrams.
     *
     * <p> The value of this socket option is a {@code Boolean} that controls
     * the <em>loopback</em> of multicast datagrams. The value of the socket
     * option represents if the option is enabled or disabled.
     *
     * <p> The exact semantics of this socket options are system dependent.
     * In particular, it is system dependent whether the loopback applies to
     * multicast datagrams sent from the socket or received by the socket.
     * For {@link StandardProtocolFamily#INET6 IPv6} sockets then it is
     * system dependent whether the option also applies to multicast datagrams
     * sent to IPv4 addresses.
     *
     * <p> The initial/default value of this socket option is {@code TRUE}. An
     * implementation allows this socket option to be set after the socket is
     * bound. Whether the socket option can be queried or changed prior to
     * binding the socket is system dependent.
     *
     * @see java.nio.channels.MulticastChannel
     */
    public static final SocketOption<Boolean> IP_MULTICAST_LOOP =
        new StdSocketOption<Boolean>("IP_MULTICAST_LOOP", Boolean.class);


    // -- IPPROTO_TCP --

    
Disable the Nagle algorithm.

 The value of this socket option is a Boolean that represents whether the option is enabled or disabled. The socket option is specific to stream-oriented sockets using the TCP/IP protocol. TCP/IP uses an algorithm known as The Nagle Algorithm to coalesce short segments and
improve network efficiency.

 The default value of this socket option is FALSE. The socket option should only be enabled in cases where it is known that the coalescing impacts performance. The socket option may be enabled at any time. In other words, the Nagle Algorithm can be disabled. Once the option is enabled, it is system dependent whether it can be subsequently disabled. If it cannot, then invoking the setOption method to disable the option has no effect. 
See Also:
/**
     * Disable the Nagle algorithm.
     *
     * <p> The value of this socket option is a {@code Boolean} that represents
     * whether the option is enabled or disabled. The socket option is specific to
     * stream-oriented sockets using the TCP/IP protocol. TCP/IP uses an algorithm
     * known as <em>The Nagle Algorithm</em> to coalesce short segments and
     * improve network efficiency.
     *
     * <p> The default value of this socket option is {@code FALSE}. The
     * socket option should only be enabled in cases where it is known that the
     * coalescing impacts performance. The socket option may be enabled at any
     * time. In other words, the Nagle Algorithm can be disabled. Once the option
     * is enabled, it is system dependent whether it can be subsequently
     * disabled. If it cannot, then invoking the {@code setOption} method to
     * disable the option has no effect.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc1122.txt">RFC&nbsp;1122:
     * Requirements for Internet Hosts -- Communication Layers</a>
     * @see Socket#setTcpNoDelay
     */
    public static final SocketOption<Boolean> TCP_NODELAY =
        new StdSocketOption<Boolean>("TCP_NODELAY", Boolean.class);


    private static class StdSocketOption<T> implements SocketOption<T> {
        private final String name;
        private final Class<T> type;
        StdSocketOption(String name, Class<T> type) {
            this.name = name;
            this.type = type;
        }
        @Override public String name() { return name; }
        @Override public Class<T> type() { return type; }
        @Override public String toString() { return name; }
    }
}