Java tutorial
/* * Copyright (c) 2007, 2016, 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; /** * 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. * * <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 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. * * <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 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. * * <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. * * <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 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. * * <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 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. * * <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. * * <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. * * <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 1349</a> and <a * href="http://www.ietf.org/rfc/rfc2474.txt">RFC 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. * * <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 * @see MulticastSocket#setInterface */ public static final SocketOption<NetworkInterface> IP_MULTICAST_IF = new StdSocketOption<NetworkInterface>( "IP_MULTICAST_IF", NetworkInterface.class); /** * 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. * * <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 * @see MulticastSocket#setLoopbackMode */ public static final SocketOption<Boolean> IP_MULTICAST_LOOP = new StdSocketOption<Boolean>("IP_MULTICAST_LOOP", Boolean.class); // -- IPPROTO_TCP -- /** * 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 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; } } }