1 /*

     2  * Copyright (c) 2000, 2017, 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.nio.channels;

    27 

    28 import java.io.IOException;

    29 import java.net.Socket;

    30 import java.net.SocketOption;

    31 import java.net.SocketAddress;

    32 import java.nio.ByteBuffer;

    33 import java.nio.channels.spi.AbstractSelectableChannel;

    34 import java.nio.channels.spi.SelectorProvider;

    35 

    36 /**

    37  * A selectable channel for stream-oriented connecting sockets.

    38  *

    39  * <p> A socket channel is created by invoking one of the {@link #open open}

    40  * methods of this class.  It is not possible to create a channel for an arbitrary,

    41  * pre-existing socket. A newly-created socket channel is open but not yet

    42  * connected.  An attempt to invoke an I/O operation upon an unconnected

    43  * channel will cause a {@link NotYetConnectedException} to be thrown.  A

    44  * socket channel can be connected by invoking its {@link #connect connect}

    45  * method; once connected, a socket channel remains connected until it is

    46  * closed.  Whether or not a socket channel is connected may be determined by

    47  * invoking its {@link #isConnected isConnected} method.

    48  *

    49  * <p> Socket channels support <i>non-blocking connection:</i>&nbsp;A socket

    50  * channel may be created and the process of establishing the link to the

    51  * remote socket may be initiated via the {@link #connect connect} method for

    52  * later completion by the {@link #finishConnect finishConnect} method.

    53  * Whether or not a connection operation is in progress may be determined by

    54  * invoking the {@link #isConnectionPending isConnectionPending} method.

    55  *

    56  * <p> Socket channels support <i>asynchronous shutdown,</i> which is similar

    57  * to the asynchronous close operation specified in the {@link Channel} class.

    58  * If the input side of a socket is shut down by one thread while another

    59  * thread is blocked in a read operation on the socket's channel, then the read

    60  * operation in the blocked thread will complete without reading any bytes and

    61  * will return {@code -1}.  If the output side of a socket is shut down by one

    62  * thread while another thread is blocked in a write operation on the socket's

    63  * channel, then the blocked thread will receive an {@link

    64  * AsynchronousCloseException}.

    65  *

    66  * <p> Socket options are configured using the {@link #setOption(SocketOption,Object)

    67  * setOption} method. Socket channels support the following options:

    68  * <blockquote>

    69  * <table class="striped">

    70  * <caption style="display:none">Socket options</caption>

    71  * <thead>

    72  *   <tr>

    73  *     <th scope="col">Option Name</th>

    74  *     <th scope="col">Description</th>

    75  *   </tr>

    76  * </thead>

    77  * <tbody>

    78  *   <tr>

    79  *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_SNDBUF SO_SNDBUF} </th>

    80  *     <td> The size of the socket send buffer </td>

    81  *   </tr>

    82  *   <tr>

    83  *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </th>

    84  *     <td> The size of the socket receive buffer </td>

    85  *   </tr>

    86  *   <tr>

    87  *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_KEEPALIVE SO_KEEPALIVE} </th>

    88  *     <td> Keep connection alive </td>

    89  *   </tr>

    90  *   <tr>

    91  *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </th>

    92  *     <td> Re-use address </td>

    93  *   </tr>

    94  *   <tr>

    95  *     <th scope="row"> {@link java.net.StandardSocketOptions#SO_LINGER SO_LINGER} </th>

    96  *     <td> Linger on close if data is present (when configured in blocking mode

    97  *          only) </td>

    98  *   </tr>

    99  *   <tr>

   100  *     <th scope="row"> {@link java.net.StandardSocketOptions#TCP_NODELAY TCP_NODELAY} </th>

   101  *     <td> Disable the Nagle algorithm </td>

   102  *   </tr>

   103  * </tbody>

   104  * </table>

   105  * </blockquote>

   106  * Additional (implementation specific) options may also be supported.

   107  *

   108  * <p> Socket channels are safe for use by multiple concurrent threads.  They

   109  * support concurrent reading and writing, though at most one thread may be

   110  * reading and at most one thread may be writing at any given time.  The {@link

   111  * #connect connect} and {@link #finishConnect finishConnect} methods are

   112  * mutually synchronized against each other, and an attempt to initiate a read

   113  * or write operation while an invocation of one of these methods is in

   114  * progress will block until that invocation is complete.  </p>

   115  *

   116  * @author Mark Reinhold

   117  * @author JSR-51 Expert Group

   118  * @since 1.4

   119  */

   120 

   121 public abstract class SocketChannel

   122     extends AbstractSelectableChannel

   123     implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, NetworkChannel

   124 {

   125 

   126     /**

   127      * Initializes a new instance of this class.

   128      *

   129      * @param  provider

   130      *         The provider that created this channel

   131      */

   132     protected SocketChannel(SelectorProvider provider) {

   133         super(provider);

   134     }

   135 

   136     /**

   137      * Opens a socket channel.

   138      *

   139      * <p> The new channel is created by invoking the {@link

   140      * java.nio.channels.spi.SelectorProvider#openSocketChannel

   141      * openSocketChannel} method of the system-wide default {@link

   142      * java.nio.channels.spi.SelectorProvider} object.  </p>

   143      *

   144      * @return  A new socket channel

   145      *

   146      * @throws  IOException

   147      *          If an I/O error occurs

   148      */

   149     public static SocketChannel open() throws IOException {

   150         return SelectorProvider.provider().openSocketChannel();

   151     }

   152 

   153     /**

   154      * Opens a socket channel and connects it to a remote address.

   155      *

   156      * <p> This convenience method works as if by invoking the {@link #open()}

   157      * method, invoking the {@link #connect(SocketAddress) connect} method upon

   158      * the resulting socket channel, passing it {@code remote}, and then

   159      * returning that channel.  </p>

   160      *

   161      * @param  remote

   162      *         The remote address to which the new channel is to be connected

   163      *

   164      * @return  A new, and connected, socket channel

   165      *

   166      * @throws  AsynchronousCloseException

   167      *          If another thread closes this channel

   168      *          while the connect operation is in progress

   169      *

   170      * @throws  ClosedByInterruptException

   171      *          If another thread interrupts the current thread

   172      *          while the connect operation is in progress, thereby

   173      *          closing the channel and setting the current thread's

   174      *          interrupt status

   175      *

   176      * @throws  UnresolvedAddressException

   177      *          If the given remote address is not fully resolved

   178      *

   179      * @throws  UnsupportedAddressTypeException

   180      *          If the type of the given remote address is not supported

   181      *

   182      * @throws  SecurityException

   183      *          If a security manager has been installed

   184      *          and it does not permit access to the given remote endpoint

   185      *

   186      * @throws  IOException

   187      *          If some other I/O error occurs

   188      */

   189     public static SocketChannel open(SocketAddress remote)

   190         throws IOException

   191     {

   192         SocketChannel sc = open();

   193         try {

   194             sc.connect(remote);

   195         } catch (Throwable x) {

   196             try {

   197                 sc.close();

   198             } catch (Throwable suppressed) {

   199                 x.addSuppressed(suppressed);

   200             }

   201             throw x;

   202         }

   203         assert sc.isConnected();

   204         return sc;

   205     }

   206 

   207     /**

   208      * Returns an operation set identifying this channel's supported

   209      * operations.

   210      *

   211      * <p> Socket channels support connecting, reading, and writing, so this

   212      * method returns {@code (}{@link SelectionKey#OP_CONNECT}

   213      * {@code |} {@link SelectionKey#OP_READ} {@code |} {@link

   214      * SelectionKey#OP_WRITE}{@code )}.

   215      *

   216      * @return  The valid-operation set

   217      */

   218     public final int validOps() {

   219         return (SelectionKey.OP_READ

   220                 | SelectionKey.OP_WRITE

   221                 | SelectionKey.OP_CONNECT);

   222     }

   223 

   224 

   225     // -- Socket-specific operations --

   226 

   227     /**

   228      * @throws  ConnectionPendingException

   229      *          If a non-blocking connect operation is already in progress on

   230      *          this channel

   231      * @throws  AlreadyBoundException               {@inheritDoc}

   232      * @throws  UnsupportedAddressTypeException     {@inheritDoc}

   233      * @throws  ClosedChannelException              {@inheritDoc}

   234      * @throws  IOException                         {@inheritDoc}

   235      * @throws  SecurityException

   236      *          If a security manager has been installed and its

   237      *          {@link SecurityManager#checkListen checkListen} method denies

   238      *          the operation

   239      *

   240      * @since 1.7

   241      */

   242     @Override

   243     public abstract SocketChannel bind(SocketAddress local)

   244         throws IOException;

   245 

   246     /**

   247      * @throws  UnsupportedOperationException           {@inheritDoc}

   248      * @throws  IllegalArgumentException                {@inheritDoc}

   249      * @throws  ClosedChannelException                  {@inheritDoc}

   250      * @throws  IOException                             {@inheritDoc}

   251      *

   252      * @since 1.7

   253      */

   254     @Override

   255     public abstract <T> SocketChannel setOption(SocketOption<T> name, T value)

   256         throws IOException;

   257 

   258     /**

   259      * Shutdown the connection for reading without closing the channel.

   260      *

   261      * <p> Once shutdown for reading then further reads on the channel will

   262      * return {@code -1}, the end-of-stream indication. If the input side of the

   263      * connection is already shutdown then invoking this method has no effect.

   264      *

   265      * @return  The channel

   266      *

   267      * @throws  NotYetConnectedException

   268      *          If this channel is not yet connected

   269      * @throws  ClosedChannelException

   270      *          If this channel is closed

   271      * @throws  IOException

   272      *          If some other I/O error occurs

   273      *

   274      * @since 1.7

   275      */

   276     public abstract SocketChannel shutdownInput() throws IOException;

   277 

   278     /**

   279      * Shutdown the connection for writing without closing the channel.

   280      *

   281      * <p> Once shutdown for writing then further attempts to write to the

   282      * channel will throw {@link ClosedChannelException}. If the output side of

   283      * the connection is already shutdown then invoking this method has no

   284      * effect.

   285      *

   286      * @return  The channel

   287      *

   288      * @throws  NotYetConnectedException

   289      *          If this channel is not yet connected

   290      * @throws  ClosedChannelException

   291      *          If this channel is closed

   292      * @throws  IOException

   293      *          If some other I/O error occurs

   294      *

   295      * @since 1.7

   296      */

   297     public abstract SocketChannel shutdownOutput() throws IOException;

   298 

   299     /**

   300      * Retrieves a socket associated with this channel.

   301      *

   302      * <p> The returned object will not declare any public methods that are not

   303      * declared in the {@link java.net.Socket} class.  </p>

   304      *

   305      * @return  A socket associated with this channel

   306      */

   307     public abstract Socket socket();

   308 

   309     /**

   310      * Tells whether or not this channel's network socket is connected.

   311      *

   312      * @return  {@code true} if, and only if, this channel's network socket

   313      *          is {@link #isOpen open} and connected

   314      */

   315     public abstract boolean isConnected();

   316 

   317     /**

   318      * Tells whether or not a connection operation is in progress on this

   319      * channel.

   320      *

   321      * @return  {@code true} if, and only if, a connection operation has been

   322      *          initiated on this channel but not yet completed by invoking the

   323      *          {@link #finishConnect finishConnect} method

   324      */

   325     public abstract boolean isConnectionPending();

   326 

   327     /**

   328      * Connects this channel's socket.

   329      *

   330      * <p> If this channel is in non-blocking mode then an invocation of this

   331      * method initiates a non-blocking connection operation.  If the connection

   332      * is established immediately, as can happen with a local connection, then

   333      * this method returns {@code true}.  Otherwise this method returns

   334      * {@code false} and the connection operation must later be completed by

   335      * invoking the {@link #finishConnect finishConnect} method.

   336      *

   337      * <p> If this channel is in blocking mode then an invocation of this

   338      * method will block until the connection is established or an I/O error

   339      * occurs.

   340      *

   341      * <p> This method performs exactly the same security checks as the {@link

   342      * java.net.Socket} class.  That is, if a security manager has been

   343      * installed then this method verifies that its {@link

   344      * java.lang.SecurityManager#checkConnect checkConnect} method permits

   345      * connecting to the address and port number of the given remote endpoint.

   346      *

   347      * <p> This method may be invoked at any time.  If a read or write

   348      * operation upon this channel is invoked while an invocation of this

   349      * method is in progress then that operation will first block until this

   350      * invocation is complete.  If a connection attempt is initiated but fails,

   351      * that is, if an invocation of this method throws a checked exception,

   352      * then the channel will be closed.  </p>

   353      *

   354      * @param  remote

   355      *         The remote address to which this channel is to be connected

   356      *

   357      * @return  {@code true} if a connection was established,

   358      *          {@code false} if this channel is in non-blocking mode

   359      *          and the connection operation is in progress

   360      *

   361      * @throws  AlreadyConnectedException

   362      *          If this channel is already connected

   363      *

   364      * @throws  ConnectionPendingException

   365      *          If a non-blocking connection operation is already in progress

   366      *          on this channel

   367      *

   368      * @throws  ClosedChannelException

   369      *          If this channel is closed

   370      *

   371      * @throws  AsynchronousCloseException

   372      *          If another thread closes this channel

   373      *          while the connect operation is in progress

   374      *

   375      * @throws  ClosedByInterruptException

   376      *          If another thread interrupts the current thread

   377      *          while the connect operation is in progress, thereby

   378      *          closing the channel and setting the current thread's

   379      *          interrupt status

   380      *

   381      * @throws  UnresolvedAddressException

   382      *          If the given remote address is not fully resolved

   383      *

   384      * @throws  UnsupportedAddressTypeException

   385      *          If the type of the given remote address is not supported

   386      *

   387      * @throws  SecurityException

   388      *          If a security manager has been installed

   389      *          and it does not permit access to the given remote endpoint

   390      *

   391      * @throws  IOException

   392      *          If some other I/O error occurs

   393      */

   394     public abstract boolean connect(SocketAddress remote) throws IOException;

   395 

   396     /**

   397      * Finishes the process of connecting a socket channel.

   398      *

   399      * <p> A non-blocking connection operation is initiated by placing a socket

   400      * channel in non-blocking mode and then invoking its {@link #connect

   401      * connect} method.  Once the connection is established, or the attempt has

   402      * failed, the socket channel will become connectable and this method may

   403      * be invoked to complete the connection sequence.  If the connection

   404      * operation failed then invoking this method will cause an appropriate

   405      * {@link java.io.IOException} to be thrown.

   406      *

   407      * <p> If this channel is already connected then this method will not block

   408      * and will immediately return {@code true}.  If this channel is in

   409      * non-blocking mode then this method will return {@code false} if the

   410      * connection process is not yet complete.  If this channel is in blocking

   411      * mode then this method will block until the connection either completes

   412      * or fails, and will always either return {@code true} or throw a checked

   413      * exception describing the failure.

   414      *

   415      * <p> This method may be invoked at any time.  If a read or write

   416      * operation upon this channel is invoked while an invocation of this

   417      * method is in progress then that operation will first block until this

   418      * invocation is complete.  If a connection attempt fails, that is, if an

   419      * invocation of this method throws a checked exception, then the channel

   420      * will be closed.  </p>

   421      *

   422      * @return  {@code true} if, and only if, this channel's socket is now

   423      *          connected

   424      *

   425      * @throws  NoConnectionPendingException

   426      *          If this channel is not connected and a connection operation

   427      *          has not been initiated

   428      *

   429      * @throws  ClosedChannelException

   430      *          If this channel is closed

   431      *

   432      * @throws  AsynchronousCloseException

   433      *          If another thread closes this channel

   434      *          while the connect operation is in progress

   435      *

   436      * @throws  ClosedByInterruptException

   437      *          If another thread interrupts the current thread

   438      *          while the connect operation is in progress, thereby

   439      *          closing the channel and setting the current thread's

   440      *          interrupt status

   441      *

   442      * @throws  IOException

   443      *          If some other I/O error occurs

   444      */

   445     public abstract boolean finishConnect() throws IOException;

   446 

   447     /**

   448      * Returns the remote address to which this channel's socket is connected.

   449      *

   450      * <p> Where the channel is bound and connected to an Internet Protocol

   451      * socket address then the return value from this method is of type {@link

   452      * java.net.InetSocketAddress}.

   453      *

   454      * @return  The remote address; {@code null} if the channel's socket is not

   455      *          connected

   456      *

   457      * @throws  ClosedChannelException

   458      *          If the channel is closed

   459      * @throws  IOException

   460      *          If an I/O error occurs

   461      *

   462      * @since 1.7

   463      */

   464     public abstract SocketAddress getRemoteAddress() throws IOException;

   465 

   466     // -- ByteChannel operations --

   467 

   468     /**

   469      * @throws  NotYetConnectedException

   470      *          If this channel is not yet connected

   471      */

   472     public abstract int read(ByteBuffer dst) throws IOException;

   473 

   474     /**

   475      * @throws  NotYetConnectedException

   476      *          If this channel is not yet connected

   477      */

   478     public abstract long read(ByteBuffer[] dsts, int offset, int length)

   479         throws IOException;

   480 

   481     /**

   482      * @throws  NotYetConnectedException

   483      *          If this channel is not yet connected

   484      */

   485     public final long read(ByteBuffer[] dsts) throws IOException {

   486         return read(dsts, 0, dsts.length);

   487     }

   488 

   489     /**

   490      * @throws  NotYetConnectedException

   491      *          If this channel is not yet connected

   492      */

   493     public abstract int write(ByteBuffer src) throws IOException;

   494 

   495     /**

   496      * @throws  NotYetConnectedException

   497      *          If this channel is not yet connected

   498      */

   499     public abstract long write(ByteBuffer[] srcs, int offset, int length)

   500         throws IOException;

   501 

   502     /**

   503      * @throws  NotYetConnectedException

   504      *          If this channel is not yet connected

   505      */

   506     public final long write(ByteBuffer[] srcs) throws IOException {

   507         return write(srcs, 0, srcs.length);

   508     }

   509 

   510     /**

   511      * {@inheritDoc}

   512      * <p>

   513      * If there is a security manager set, its {@code checkConnect} method is

   514      * called with the local address and {@code -1} as its arguments to see

   515      * if the operation is allowed. If the operation is not allowed,

   516      * a {@code SocketAddress} representing the

   517      * {@link java.net.InetAddress#getLoopbackAddress loopback} address and the

   518      * local port of the channel's socket is returned.

   519      *

   520      * @return  The {@code SocketAddress} that the socket is bound to, or the

   521      *          {@code SocketAddress} representing the loopback address if

   522      *          denied by the security manager, or {@code null} if the

   523      *          channel's socket is not bound

   524      *

   525      * @throws  ClosedChannelException     {@inheritDoc}

   526      * @throws  IOException                {@inheritDoc}

   527      */

   528     @Override

   529     public abstract SocketAddress getLocalAddress() throws IOException;

   530 

   531 }