/* * Copyright (c) 2000, 2011, 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.Socket;import java.net.SocketOption;import java.net.SocketAddress;import java.nio.ByteBuffer;import java.nio.channels.spi.AbstractSelectableChannel;import java.nio.channels.spi.SelectorProvider; /** * A selectable channel for stream-oriented connecting sockets. * * <p> A socket channel is created by invoking one of the {@link #open open} * methods of this class.  It is not possible to create a channel for an arbitrary, * pre-existing socket. A newly-created socket channel is open but not yet * connected.  An attempt to invoke an I/O operation upon an unconnected * channel will cause a {@link NotYetConnectedException} to be thrown.  A * socket channel can be connected by invoking its {@link #connect connect} * method; once connected, a socket channel remains connected until it is * closed.  Whether or not a socket channel is connected may be determined by * invoking its {@link #isConnected isConnected} method. * * <p> Socket channels support <i>non-blocking connection:</i>&nbsp;A socket * channel may be created and the process of establishing the link to the * remote socket may be initiated via the {@link #connect connect} method for * later completion by the {@link #finishConnect finishConnect} method. * Whether or not a connection operation is in progress may be determined by * invoking the {@link #isConnectionPending isConnectionPending} method. * * <p> Socket channels support <i>asynchronous shutdown,</i> which is similar * to the asynchronous close operation specified in the {@link Channel} class. * If the input side of a socket is shut down by one thread while another * thread is blocked in a read operation on the socket's channel, then the read * operation in the blocked thread will complete without reading any bytes and * will return <tt>-1</tt>.  If the output side of a socket is shut down by one * thread while another thread is blocked in a write operation on the socket's * channel, then the blocked thread will receive an {@link * AsynchronousCloseException}. * * <p> Socket options are configured using the {@link #setOption(SocketOption,Object) * setOption} method. Socket channels support the following options: * <blockquote> * <table border> *   <tr> *     <th>Option Name</th> *     <th>Description</th> *   </tr> *   <tr> *     <td> {@link java.net.StandardSocketOptions#SO_SNDBUF SO_SNDBUF} </td> *     <td> The size of the socket send buffer </td> *   </tr> *   <tr> *     <td> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </td> *     <td> The size of the socket receive buffer </td> *   </tr> *   <tr> *     <td> {@link java.net.StandardSocketOptions#SO_KEEPALIVE SO_KEEPALIVE} </td> *     <td> Keep connection alive </td> *   </tr> *   <tr> *     <td> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </td> *     <td> Re-use address </td> *   </tr> *   <tr> *     <td> {@link java.net.StandardSocketOptions#SO_LINGER SO_LINGER} </td> *     <td> Linger on close if data is present (when configured in blocking mode *          only) </td> *   </tr> *   <tr> *     <td> {@link java.net.StandardSocketOptions#TCP_NODELAY TCP_NODELAY} </td> *     <td> Disable the Nagle algorithm </td> *   </tr> * </table> * </blockquote> * Additional (implementation specific) options may also be supported. * * <p> Socket channels are safe for use by multiple concurrent threads.  They * support concurrent reading and writing, though at most one thread may be * reading and at most one thread may be writing at any given time.  The {@link * #connect connect} and {@link #finishConnect finishConnect} methods are * mutually synchronized against each other, and an attempt to initiate a read * or write operation while an invocation of one of these methods is in * progress will block until that invocation is complete.  </p> * * @author Mark Reinhold * @author JSR-51 Expert Group * @since 1.4 */ public abstract class SocketChannel    extends AbstractSelectableChannel    implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, NetworkChannel{     /**     * Initializes a new instance of this class.     */    protected SocketChannel(SelectorProvider provider) {        super(provider);    }     /**     * Opens a socket channel.     *     * <p> The new channel is created by invoking the {@link     * java.nio.channels.spi.SelectorProvider#openSocketChannel     * openSocketChannel} method of the system-wide default {@link     * java.nio.channels.spi.SelectorProvider} object.  </p>     *     * @return  A new socket channel     *     * @throws  IOException     *          If an I/O error occurs     */    public static SocketChannel open() throws IOException {        return SelectorProvider.provider().openSocketChannel();    }     /**     * Opens a socket channel and connects it to a remote address.     *     * <p> This convenience method works as if by invoking the {@link #open()}     * method, invoking the {@link #connect(SocketAddress) connect} method upon     * the resulting socket channel, passing it <tt>remote</tt>, and then     * returning that channel.  </p>     *     * @param  remote     *         The remote address to which the new channel is to be connected     *     * @throws  AsynchronousCloseException     *          If another thread closes this channel     *          while the connect operation is in progress     *     * @throws  ClosedByInterruptException     *          If another thread interrupts the current thread     *          while the connect operation is in progress, thereby     *          closing the channel and setting the current thread's     *          interrupt status     *     * @throws  UnresolvedAddressException     *          If the given remote address is not fully resolved     *     * @throws  UnsupportedAddressTypeException     *          If the type of the given remote address is not supported     *     * @throws  SecurityException     *          If a security manager has been installed     *          and it does not permit access to the given remote endpoint     *     * @throws  IOException     *          If some other I/O error occurs     */    public static SocketChannel open(SocketAddress remote)        throws IOException    {        SocketChannel sc = open();        try {            sc.connect(remote);        } catch (Throwable x) {            try {                sc.close();            } catch (Throwable suppressed) {                x.addSuppressed(suppressed);            }            throw x;        }        assert sc.isConnected();        return sc;    }     /**     * Returns an operation set identifying this channel's supported     * operations.     *     * <p> Socket channels support connecting, reading, and writing, so this     * method returns <tt>(</tt>{@link SelectionKey#OP_CONNECT}     * <tt>|</tt>&nbsp;{@link SelectionKey#OP_READ} <tt>|</tt>&nbsp;{@link     * SelectionKey#OP_WRITE}<tt>)</tt>.  </p>     *     * @return  The valid-operation set     */    public final int validOps() {        return (SelectionKey.OP_READ                | SelectionKey.OP_WRITE                | SelectionKey.OP_CONNECT);    }      // -- Socket-specific operations --     /**     * @throws  ConnectionPendingException     *          If a non-blocking connect operation is already in progress on     *          this channel     * @throws  AlreadyBoundException               {@inheritDoc}     * @throws  UnsupportedAddressTypeException     {@inheritDoc}     * @throws  ClosedChannelException              {@inheritDoc}     * @throws  IOException                         {@inheritDoc}     *     * @since 1.7     */    @Override    public abstract SocketChannel bind(SocketAddress local)        throws IOException;     /**     * @throws  UnsupportedOperationException           {@inheritDoc}     * @throws  IllegalArgumentException                {@inheritDoc}     * @throws  ClosedChannelException                  {@inheritDoc}     * @throws  IOException                             {@inheritDoc}     *     * @since 1.7     */    @Override    public abstract <T> SocketChannel setOption(SocketOption<T> name, T value)        throws IOException;     /**     * Shutdown the connection for reading without closing the channel.     *     * <p> Once shutdown for reading then further reads on the channel will     * return {@code -1}, the end-of-stream indication. If the input side of the     * connection is already shutdown then invoking this method has no effect.     *     * @return  The channel     *     * @throws  NotYetConnectedException     *          If this channel is not yet connected     * @throws  ClosedChannelException     *          If this channel is closed     * @throws  IOException     *          If some other I/O error occurs     *     * @since 1.7     */    public abstract SocketChannel shutdownInput() throws IOException;     /**     * Shutdown the connection for writing without closing the channel.     *     * <p> Once shutdown for writing then further attempts to write to the     * channel will throw {@link ClosedChannelException}. If the output side of     * the connection is already shutdown then invoking this method has no     * effect.     *     * @return  The channel     *     * @throws  NotYetConnectedException     *          If this channel is not yet connected     * @throws  ClosedChannelException     *          If this channel is closed     * @throws  IOException     *          If some other I/O error occurs     *     * @since 1.7     */    public abstract SocketChannel shutdownOutput() throws IOException;     /**     * Retrieves a socket associated with this channel.     *     * <p> The returned object will not declare any public methods that are not     * declared in the {@link java.net.Socket} class.  </p>     *     * @return  A socket associated with this channel     */    public abstract Socket socket();     /**     * Tells whether or not this channel's network socket is connected.     *     * @return  <tt>true</tt> if, and only if, this channel's network socket     *          is {@link #isOpen open} and connected     */    public abstract boolean isConnected();     /**     * Tells whether or not a connection operation is in progress on this     * channel.  </p>     *     * @return  <tt>true</tt> if, and only if, a connection operation has been     *          initiated on this channel but not yet completed by invoking the     *          {@link #finishConnect finishConnect} method     */    public abstract boolean isConnectionPending();     /**     * Connects this channel's socket.     *     * <p> If this channel is in non-blocking mode then an invocation of this     * method initiates a non-blocking connection operation.  If the connection     * is established immediately, as can happen with a local connection, then     * this method returns <tt>true</tt>.  Otherwise this method returns     * <tt>false</tt> and the connection operation must later be completed by     * invoking the {@link #finishConnect finishConnect} method.     *     * <p> If this channel is in blocking mode then an invocation of this     * method will block until the connection is established or an I/O error     * occurs.     *     * <p> This method performs exactly the same security checks as the {@link     * java.net.Socket} class.  That is, if a security manager has been     * installed then this method verifies that its {@link     * java.lang.SecurityManager#checkConnect checkConnect} method permits     * connecting to the address and port number of the given remote endpoint.     *     * <p> This method may be invoked at any time.  If a read or write     * operation upon this channel is invoked while an invocation of this     * method is in progress then that operation will first block until this     * invocation is complete.  If a connection attempt is initiated but fails,     * that is, if an invocation of this method throws a checked exception,     * then the channel will be closed.  </p>     *     * @param  remote     *         The remote address to which this channel is to be connected     *     * @return  <tt>true</tt> if a connection was established,     *          <tt>false</tt> if this channel is in non-blocking mode     *          and the connection operation is in progress     *     * @throws  AlreadyConnectedException     *          If this channel is already connected     *     * @throws  ConnectionPendingException     *          If a non-blocking connection operation is already in progress     *          on this channel     *     * @throws  ClosedChannelException     *          If this channel is closed     *     * @throws  AsynchronousCloseException     *          If another thread closes this channel     *          while the connect operation is in progress     *     * @throws  ClosedByInterruptException     *          If another thread interrupts the current thread     *          while the connect operation is in progress, thereby     *          closing the channel and setting the current thread's     *          interrupt status     *     * @throws  UnresolvedAddressException     *          If the given remote address is not fully resolved     *     * @throws  UnsupportedAddressTypeException     *          If the type of the given remote address is not supported     *     * @throws  SecurityException     *          If a security manager has been installed     *          and it does not permit access to the given remote endpoint     *     * @throws  IOException     *          If some other I/O error occurs     */    public abstract boolean connect(SocketAddress remote) throws IOException;     /**     * Finishes the process of connecting a socket channel.     *     * <p> A non-blocking connection operation is initiated by placing a socket     * channel in non-blocking mode and then invoking its {@link #connect     * connect} method.  Once the connection is established, or the attempt has     * failed, the socket channel will become connectable and this method may     * be invoked to complete the connection sequence.  If the connection     * operation failed then invoking this method will cause an appropriate     * {@link java.io.IOException} to be thrown.     *     * <p> If this channel is already connected then this method will not block     * and will immediately return <tt>true</tt>.  If this channel is in     * non-blocking mode then this method will return <tt>false</tt> if the     * connection process is not yet complete.  If this channel is in blocking     * mode then this method will block until the connection either completes     * or fails, and will always either return <tt>true</tt> or throw a checked     * exception describing the failure.     *     * <p> This method may be invoked at any time.  If a read or write     * operation upon this channel is invoked while an invocation of this     * method is in progress then that operation will first block until this     * invocation is complete.  If a connection attempt fails, that is, if an     * invocation of this method throws a checked exception, then the channel     * will be closed.  </p>     *     * @return  <tt>true</tt> if, and only if, this channel's socket is now     *          connected     *     * @throws  NoConnectionPendingException     *          If this channel is not connected and a connection operation     *          has not been initiated     *     * @throws  ClosedChannelException     *          If this channel is closed     *     * @throws  AsynchronousCloseException     *          If another thread closes this channel     *          while the connect operation is in progress     *     * @throws  ClosedByInterruptException     *          If another thread interrupts the current thread     *          while the connect operation is in progress, thereby     *          closing the channel and setting the current thread's     *          interrupt status     *     * @throws  IOException     *          If some other I/O error occurs     */    public abstract boolean finishConnect() throws IOException;     /**     * Returns the remote address to which this channel's socket is connected.     *     * <p> Where the channel is bound and connected to an Internet Protocol     * socket address then the return value from this method is of type {@link     * java.net.InetSocketAddress}.     *     * @return  The remote address; {@code null} if the channel's socket is not     *          connected     *     * @throws  ClosedChannelException     *          If the channel is closed     * @throws  IOException     *          If an I/O error occurs     *     * @since 1.7     */    public abstract SocketAddress getRemoteAddress() throws IOException;     // -- ByteChannel operations --     /**     * @throws  NotYetConnectedException     *          If this channel is not yet connected     */    public abstract int read(ByteBuffer dst) throws IOException;     /**     * @throws  NotYetConnectedException     *          If this channel is not yet connected     */    public abstract long read(ByteBuffer[] dsts, int offset, int length)        throws IOException;     /**     * @throws  NotYetConnectedException     *          If this channel is not yet connected     */    public final long read(ByteBuffer[] dsts) throws IOException {        return read(dsts, 0, dsts.length);    }     /**     * @throws  NotYetConnectedException     *          If this channel is not yet connected     */    public abstract int write(ByteBuffer src) throws IOException;     /**     * @throws  NotYetConnectedException     *          If this channel is not yet connected     */    public abstract long write(ByteBuffer[] srcs, int offset, int length)        throws IOException;     /**     * @throws  NotYetConnectedException     *          If this channel is not yet connected     */    public final long write(ByteBuffer[] srcs) throws IOException {        return write(srcs, 0, srcs.length);    } }