Java tutorial
/* * Copyright (c) 2000, 2017, 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.nio.channels; import java.io.IOException; import java.net.ServerSocket; import java.net.SocketOption; import java.net.SocketAddress; import java.nio.channels.spi.AbstractSelectableChannel; import java.nio.channels.spi.SelectorProvider; /** * A selectable channel for stream-oriented listening sockets. * * <p> A server-socket channel is created by invoking the {@link #open() open} * method of this class. It is not possible to create a channel for an arbitrary, * pre-existing {@link ServerSocket}. A newly-created server-socket channel is * open but not yet bound. An attempt to invoke the {@link #accept() accept} * method of an unbound server-socket channel will cause a {@link NotYetBoundException} * to be thrown. A server-socket channel can be bound by invoking one of the * {@link #bind(java.net.SocketAddress,int) bind} methods defined by this class. * * <p> Socket options are configured using the {@link #setOption(SocketOption,Object) * setOption} method. Server-socket channels support the following options: * <blockquote> * <table class="striped"> * <caption style="display:none">Socket options</caption> * <thead> * <tr> * <th scope="col">Option Name</th> * <th scope="col">Description</th> * </tr> * </thead> * <tbody> * <tr> * <th scope="row"> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </th> * <td> The size of the socket receive buffer </td> * </tr> * <tr> * <th scope="row"> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </th> * <td> Re-use address </td> * </tr> * </tbody> * </table> * </blockquote> * Additional (implementation specific) options may also be supported. * * <p> Server-socket channels are safe for use by multiple concurrent threads. * </p> * * @author Mark Reinhold * @author JSR-51 Expert Group * @since 1.4 */ public abstract class ServerSocketChannel extends AbstractSelectableChannel implements NetworkChannel { /** * Initializes a new instance of this class. * * @param provider * The provider that created this channel */ protected ServerSocketChannel(SelectorProvider provider) { super(provider); } /** * Opens a server-socket channel. * * <p> The new channel is created by invoking the {@link * java.nio.channels.spi.SelectorProvider#openServerSocketChannel * openServerSocketChannel} method of the system-wide default {@link * java.nio.channels.spi.SelectorProvider} object. * * <p> The new channel's socket is initially unbound; it must be bound to a * specific address via one of its socket's {@link * java.net.ServerSocket#bind(SocketAddress) bind} methods before * connections can be accepted. </p> * * @return A new socket channel * * @throws IOException * If an I/O error occurs */ public static ServerSocketChannel open() throws IOException { return SelectorProvider.provider().openServerSocketChannel(); } /** * Returns an operation set identifying this channel's supported * operations. * * <p> Server-socket channels only support the accepting of new * connections, so this method returns {@link SelectionKey#OP_ACCEPT}. * </p> * * @return The valid-operation set */ public final int validOps() { return SelectionKey.OP_ACCEPT; } // -- ServerSocket-specific operations -- /** * Binds the channel's socket to a local address and configures the socket * to listen for connections. * * <p> An invocation of this method is equivalent to the following: * <blockquote><pre> * bind(local, 0); * </pre></blockquote> * * @param local * The local address to bind the socket, or {@code null} to bind * to an automatically assigned socket address * * @return This channel * * @throws AlreadyBoundException {@inheritDoc} * @throws UnsupportedAddressTypeException {@inheritDoc} * @throws ClosedChannelException {@inheritDoc} * @throws IOException {@inheritDoc} * @throws SecurityException * If a security manager has been installed and its {@link * SecurityManager#checkListen checkListen} method denies the * operation * * @since 1.7 */ public final ServerSocketChannel bind(SocketAddress local) throws IOException { return bind(local, 0); } /** * Binds the channel's socket to a local address and configures the socket to * listen for connections. * * <p> This method is used to establish an association between the socket and * a local address. Once an association is established then the socket remains * bound until the channel is closed. * * <p> The {@code backlog} parameter is the maximum number of pending * connections on the socket. Its exact semantics are implementation specific. * In particular, an implementation may impose a maximum length or may choose * to ignore the parameter altogther. If the {@code backlog} parameter has * the value {@code 0}, or a negative value, then an implementation specific * default is used. * * @param local * The address to bind the socket, or {@code null} to bind to an * automatically assigned socket address * @param backlog * The maximum number of pending connections * * @return This channel * * @throws AlreadyBoundException * If the socket is already bound * @throws UnsupportedAddressTypeException * If the type of the given address is not supported * @throws ClosedChannelException * If this channel is closed * @throws IOException * If some other I/O error occurs * @throws SecurityException * If a security manager has been installed and its {@link * SecurityManager#checkListen checkListen} method denies the * operation * * @since 1.7 */ public abstract ServerSocketChannel bind(SocketAddress local, int backlog) throws IOException; /** * @throws UnsupportedOperationException {@inheritDoc} * @throws IllegalArgumentException {@inheritDoc} * @throws ClosedChannelException {@inheritDoc} * @throws IOException {@inheritDoc} * * @since 1.7 */ public abstract <T> ServerSocketChannel setOption(SocketOption<T> name, T value) throws IOException; /** * Retrieves a server socket associated with this channel. * * <p> The returned object will not declare any public methods that are not * declared in the {@link java.net.ServerSocket} class. </p> * * @return A server socket associated with this channel */ public abstract ServerSocket socket(); /** * Accepts a connection made to this channel's socket. * * <p> If this channel is in non-blocking mode then this method will * immediately return {@code null} if there are no pending connections. * Otherwise it will block indefinitely until a new connection is available * or an I/O error occurs. * * <p> The socket channel returned by this method, if any, will be in * blocking mode regardless of the blocking mode of this channel. * * <p> This method performs exactly the same security checks as the {@link * java.net.ServerSocket#accept accept} method of the {@link * java.net.ServerSocket} class. That is, if a security manager has been * installed then for each new connection this method verifies that the * address and port number of the connection's remote endpoint are * permitted by the security manager's {@link * java.lang.SecurityManager#checkAccept checkAccept} method. </p> * * @return The socket channel for the new connection, * or {@code null} if this channel is in non-blocking mode * and no connection is available to be accepted * * @throws ClosedChannelException * If this channel is closed * * @throws AsynchronousCloseException * If another thread closes this channel * while the accept operation is in progress * * @throws ClosedByInterruptException * If another thread interrupts the current thread * while the accept operation is in progress, thereby * closing the channel and setting the current thread's * interrupt status * * @throws NotYetBoundException * If this channel's socket has not yet been bound * * @throws SecurityException * If a security manager has been installed * and it does not permit access to the remote endpoint * of the new connection * * @throws IOException * If some other I/O error occurs */ public abstract SocketChannel accept() throws IOException; /** * {@inheritDoc} * <p> * If there is a security manager set, its {@code checkConnect} method is * called with the local address and {@code -1} as its arguments to see * if the operation is allowed. If the operation is not allowed, * a {@code SocketAddress} representing the * {@link java.net.InetAddress#getLoopbackAddress loopback} address and the * local port of the channel's socket is returned. * * @return The {@code SocketAddress} that the socket is bound to, or the * {@code SocketAddress} representing the loopback address if * denied by the security manager, or {@code null} if the * channel's socket is not bound * * @throws ClosedChannelException {@inheritDoc} * @throws IOException {@inheritDoc} */ @Override public abstract SocketAddress getLocalAddress() throws IOException; }