1 /*
   2  * Copyright (c) 2009, 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 package com.sun.nio.sctp;
  26 
  27 import java.net.SocketAddress;
  28 import java.net.InetAddress;
  29 import java.io.IOException;
  30 import java.util.Set;
  31 import java.nio.ByteBuffer;
  32 import java.nio.channels.spi.AbstractSelectableChannel;
  33 import java.nio.channels.spi.SelectorProvider;
  34 import java.nio.channels.ClosedChannelException;
  35 import java.nio.channels.SelectionKey;
  36 
  37 /**
  38  * A selectable channel for message-oriented connected SCTP sockets.
  39  *
  40  * <P> An SCTP channel can only control one SCTP association.
  41  * An {@code SCTPChannel} is created by invoking one of the
  42  * {@link #open open} methods of this class. A newly-created channel is open but
  43  * not yet connected, that is, there is no association setup with a remote peer.
  44  * An attempt to invoke an I/O operation upon an unconnected
  45  * channel will cause a {@link java.nio.channels.NotYetConnectedException} to be
  46  * thrown. An association can be setup by connecting the channel using one of
  47  * its {@link #connect connect} methods. Once connected, the channel remains
  48  * connected until it is closed. Whether or not a channel is connected may be
  49  * determined by invoking {@link #getRemoteAddresses getRemoteAddresses}.
  50  *
  51  * <p> SCTP channels support <i>non-blocking connection:</i>&nbsp;A
  52  * channel may be created and the process of establishing the link to
  53  * the remote socket may be initiated via the {@link #connect connect} method
  54  * for later completion by the {@link #finishConnect finishConnect} method.
  55  * Whether or not a connection operation is in progress may be determined by
  56  * invoking the {@link #isConnectionPending isConnectionPending} method.
  57  *
  58  * <p> Socket options are configured using the
  59  * {@link #setOption(SctpSocketOption,Object) setOption} method. An SCTP
  60  * channel support the following options:
  61  * <blockquote>
  62  * <table class="striped">
  63  *   <caption style="display:none">Socket options</caption>
  64  *   <thead>
  65  *   <tr>
  66  *     <th scope="col">Option Name</th>
  67  *     <th scope="col">Description</th>
  68  *   </tr>
  69  *   </thead>
  70  *   <tbody>
  71  *   <tr>
  72  *     <th scope="row"> {@link SctpStandardSocketOptions#SCTP_DISABLE_FRAGMENTS
  73  *                                          SCTP_DISABLE_FRAGMENTS} </th>
  74  *     <td> Enables or disables message fragmentation </td>
  75  *   </tr>
  76  *   <tr>
  77  *     <th scope="row"> {@link SctpStandardSocketOptions#SCTP_EXPLICIT_COMPLETE
  78  *                                          SCTP_EXPLICIT_COMPLETE} </th>
  79  *     <td> Enables or disables explicit message completion </td>
  80  *   </tr>
  81  *    <tr>
  82  *     <th scope="row"> {@link SctpStandardSocketOptions#SCTP_FRAGMENT_INTERLEAVE
  83  *                                          SCTP_FRAGMENT_INTERLEAVE} </th>
  84  *     <td> Controls how the presentation of messages occur for the message
  85  *          receiver </td>
  86  *   </tr>
  87  *   <tr>
  88  *     <th scope="row"> {@link SctpStandardSocketOptions#SCTP_INIT_MAXSTREAMS
  89  *                                          SCTP_INIT_MAXSTREAMS} </th>
  90  *     <td> The maximum number of streams requested by the local endpoint during
  91  *          association initialization </td>
  92  *   </tr>
  93  *   <tr>
  94  *     <th scope="row"> {@link SctpStandardSocketOptions#SCTP_NODELAY SCTP_NODELAY} </th>
  95  *     <td> Enables or disable a Nagle-like algorithm </td>
  96  *   </tr>
  97  *   <tr>
  98  *     <th scope="row"> {@link SctpStandardSocketOptions#SCTP_PRIMARY_ADDR
  99  *                                          SCTP_PRIMARY_ADDR} </th>
 100  *     <td> Requests that the local SCTP stack use the given peer address as the
 101  *          association primary </td>
 102  *   </tr>
 103  *   <tr>
 104  *     <th scope="row"> {@link SctpStandardSocketOptions#SCTP_SET_PEER_PRIMARY_ADDR
 105  *                                          SCTP_SET_PEER_PRIMARY_ADDR} </th>
 106  *     <td> Requests that the peer mark the enclosed address as the association
 107  *          primary </td>
 108  *   </tr>
 109  *   <tr>
 110  *     <th scope="row"> {@link SctpStandardSocketOptions#SO_SNDBUF
 111  *                                          SO_SNDBUF} </th>
 112  *     <td> The size of the socket send buffer </td>
 113  *   </tr>
 114  *   <tr>
 115  *     <th scope="row"> {@link SctpStandardSocketOptions#SO_RCVBUF
 116  *                                          SO_RCVBUF} </th>
 117  *     <td> The size of the socket receive buffer </td>
 118  *   </tr>
 119  *   <tr>
 120  *     <th scope="row"> {@link SctpStandardSocketOptions#SO_LINGER
 121  *                                          SO_LINGER} </th>
 122  *     <td> Linger on close if data is present (when configured in blocking mode
 123  *          only) </td>
 124  *   </tr>
 125  *   </tbody>
 126  * </table>
 127  * </blockquote>
 128  * Additional (implementation specific) options may also be supported. The list
 129  * of options supported is obtained by invoking the {@link #supportedOptions()
 130  * supportedOptions}  method.
 131  *
 132  * <p> SCTP channels are safe for use by multiple concurrent threads.
 133  * They support concurrent reading and writing, though at most one thread may be
 134  * reading and at most one thread may be writing at any given time. The
 135  * {@link #connect connect} and {@link #finishConnect
 136  * finishConnect} methods are mutually synchronized against each other, and
 137  * an attempt to initiate a send or receive operation while an invocation of one
 138  * of these methods is in progress will block until that invocation is complete.
 139  *
 140  * @since 1.7
 141  */
 142 public abstract class SctpChannel
 143     extends AbstractSelectableChannel
 144 {
 145     /**
 146      * Initializes a new instance of this class.
 147      *
 148      * @param  provider
 149      *         The selector provider for this channel
 150      */
 151     protected SctpChannel(SelectorProvider provider) {
 152         super(provider);
 153     }
 154 
 155     /**
 156      * Opens an SCTP channel.
 157      *
 158      * <P> The new channel is unbound and unconnected.
 159      *
 160      * @return  A new SCTP channel
 161      *
 162      * @throws  UnsupportedOperationException
 163      *          If the SCTP protocol is not supported
 164      *
 165      * @throws  IOException
 166      *          If an I/O error occurs
 167      */
 168     public static SctpChannel open() throws
 169         IOException {
 170         return new sun.nio.ch.sctp.SctpChannelImpl((SelectorProvider)null);
 171     }
 172 
 173     /**
 174      * Opens an SCTP channel and connects it to a remote address.
 175      *
 176      * <P> This is a convenience method and is equivalent to evaluating the
 177      * following expression:
 178      * <blockquote><pre>
 179      * open().connect(remote, maxOutStreams, maxInStreams);
 180      * </pre></blockquote>
 181      *
 182      * @param  remote
 183      *         The remote address to which the new channel is to be connected
 184      *
 185      * @param  maxOutStreams
 186      *         The number of streams that the application wishes to be able
 187      *         to send to. Must be non negative and no larger than {@code 65536}.
 188      *         {@code 0} to use the endpoints default value.
 189      *
 190      * @param  maxInStreams
 191      *         The maximum number of inbound streams the application is prepared
 192      *         to support. Must be non negative and no larger than {@code 65536}.
 193      *         {@code 0} to use the endpoints default value.
 194      *
 195      * @return  A new SCTP channel connected to the given address
 196      *
 197      * @throws  java.nio.channels.AsynchronousCloseException
 198      *          If another thread closes this channel
 199      *          while the connect operation is in progress
 200      *
 201      * @throws  java.nio.channels.ClosedByInterruptException
 202      *          If another thread interrupts the current thread
 203      *          while the connect operation is in progress, thereby
 204      *          closing the channel and setting the current thread's
 205      *          interrupt status
 206      *
 207      * @throws  java.nio.channels.UnresolvedAddressException
 208      *          If the given remote address is not fully resolved
 209      *
 210      * @throws  java.nio.channels.UnsupportedAddressTypeException
 211      *          If the type of the given remote address is not supported
 212      *
 213      * @throws  SecurityException
 214      *          If a security manager has been installed
 215      *          and it does not permit access to the given remote peer
 216      *
 217      * @throws  UnsupportedOperationException
 218      *          If the SCTP protocol is not supported
 219      *
 220      * @throws  IOException
 221      *          If some other I/O error occurs
 222      */
 223     public static SctpChannel open(SocketAddress remote, int maxOutStreams,
 224                    int maxInStreams) throws IOException {
 225         SctpChannel ssc = SctpChannel.open();
 226         ssc.connect(remote, maxOutStreams, maxInStreams);
 227         return ssc;
 228     }
 229 
 230     /**
 231      * Returns the association on this channel's socket.
 232      *
 233      * @return  the association, or {@code null} if the channel's socket is not
 234      *          connected.
 235      *
 236      * @throws  ClosedChannelException
 237      *          If the channel is closed
 238      *
 239      * @throws  IOException
 240      *          If some other I/O error occurs
 241      */
 242     public abstract Association association() throws IOException;
 243 
 244     /**
 245      * Binds the channel's socket to a local address.
 246      *
 247      * <P> This method is used to establish a relationship between the socket
 248      * and the local addresses. Once a relationship is established then
 249      * the socket remains bound until the channel is closed. This relationship
 250      * may not necesssarily be with the address {@code local} as it may be removed
 251      * by {@link #unbindAddress unbindAddress}, but there will always be at least
 252      * one local address bound to the channel's socket once an invocation of
 253      * this method successfully completes.
 254      *
 255      * <P> Once the channel's socket has been successfully bound to a specific
 256      * address, that is not automatically assigned, more addresses
 257      * may be bound to it using {@link #bindAddress bindAddress}, or removed
 258      * using {@link #unbindAddress unbindAddress}.
 259      *
 260      * @param  local
 261      *         The local address to bind the socket, or {@code null} to
 262      *         bind the socket to an automatically assigned socket address
 263      *
 264      * @return  This channel
 265      *
 266      * @throws  java.nio.channels.AlreadyConnectedException
 267      *          If this channel is already connected
 268      *
 269      * @throws  java.nio.channels.ClosedChannelException
 270      *          If this channel is closed
 271      *
 272      * @throws  java.nio.channels.ConnectionPendingException
 273      *          If a non-blocking connection operation is already in progress on this channel
 274      *
 275      * @throws  java.nio.channels.AlreadyBoundException
 276      *          If this channel is already bound
 277      *
 278      * @throws  java.nio.channels.UnsupportedAddressTypeException
 279      *          If the type of the given address is not supported
 280      *
 281      * @throws  IOException
 282      *          If some other I/O error occurs
 283      *
 284      * @throws  SecurityException
 285      *          If a security manager has been installed and its
 286      *          {@link SecurityManager#checkListen checkListen} method denies
 287      *          the operation
 288      */
 289     public abstract SctpChannel bind(SocketAddress local)
 290         throws IOException;
 291 
 292     /**
 293      * Adds the given address to the bound addresses for the channel's
 294      * socket.
 295      *
 296      * <P> The given address must not be the {@link
 297      * java.net.InetAddress#isAnyLocalAddress wildcard} address.
 298      * The channel must be first bound using {@link #bind bind} before
 299      * invoking this method, otherwise {@link
 300      * java.nio.channels.NotYetBoundException} is thrown. The {@link #bind bind}
 301      * method takes a {@code SocketAddress} as its argument which typically
 302      * contains a port number as well as an address. Addresses subquently bound
 303      * using this method are simply addresses as the SCTP port number remains
 304      * the same for the lifetime of the channel.
 305      *
 306      * <P> Adding addresses to a connected association is optional functionality.
 307      * If the endpoint supports dynamic address reconfiguration then it may
 308      * send the appropriate message to the peer to change the peers address
 309      * lists.
 310      *
 311      * @param  address
 312      *         The address to add to the bound addresses for the socket
 313      *
 314      * @return  This channel
 315      *
 316      * @throws  java.nio.channels.ClosedChannelException
 317      *          If this channel is closed
 318      *
 319      * @throws  java.nio.channels.ConnectionPendingException
 320      *          If a non-blocking connection operation is already in progress on
 321      *          this channel
 322      *
 323      * @throws  java.nio.channels.NotYetBoundException
 324      *          If this channel is not yet bound
 325      *
 326      * @throws  java.nio.channels.AlreadyBoundException
 327      *          If this channel is already bound to the given address
 328      *
 329      * @throws  IllegalArgumentException
 330      *          If address is {@code null} or the {@link
 331      *          java.net.InetAddress#isAnyLocalAddress wildcard} address
 332      *
 333      * @throws  IOException
 334      *          If some other I/O error occurs
 335      */
 336     public abstract SctpChannel bindAddress(InetAddress address)
 337          throws IOException;
 338 
 339     /**
 340      * Removes the given address from the bound addresses for the channel's
 341      * socket.
 342      *
 343      * <P> The given address must not be the {@link
 344      * java.net.InetAddress#isAnyLocalAddress wildcard} address.
 345      * The channel must be first bound using {@link #bind bind} before
 346      * invoking this method, otherwise {@link java.nio.channels.NotYetBoundException}
 347      * is thrown. If this method is invoked on a channel that does not have
 348      * {@code address} as one of its bound addresses or that has only one
 349      * local address bound to it, then this method throws
 350      * {@link IllegalUnbindException}.
 351      * The initial address that the channel's socket is bound to using {@link
 352      * #bind bind} may be removed from the bound addresses for the channel's socket.
 353      *
 354      * <P> Removing addresses from a connected association is optional
 355      * functionality. If the endpoint supports dynamic address reconfiguration
 356      * then it may send the appropriate message to the peer to change the peers
 357      * address lists.
 358      *
 359      * @param  address
 360      *         The address to remove from the bound addresses for the socket
 361      *
 362      * @return  This channel
 363      *
 364      * @throws  java.nio.channels.ClosedChannelException
 365      *          If this channel is closed
 366      *
 367      * @throws  java.nio.channels.ConnectionPendingException
 368      *          If a non-blocking connection operation is already in progress on
 369      *          this channel
 370      *
 371      * @throws  java.nio.channels.NotYetBoundException
 372      *          If this channel is not yet bound
 373      *
 374      * @throws  IllegalArgumentException
 375      *          If address is {@code null} or the {@link
 376      *          java.net.InetAddress#isAnyLocalAddress wildcard} address
 377      *
 378      * @throws  IllegalUnbindException
 379      *          If {@code address} is not bound to the channel's socket. or
 380      *          the channel has only one address bound to it
 381      *
 382      * @throws  IOException
 383      *          If some other I/O error occurs
 384      */
 385     public abstract SctpChannel unbindAddress(InetAddress address)
 386          throws IOException;
 387 
 388     /**
 389      * Connects this channel's socket.
 390      *
 391      * <P> If this channel is in non-blocking mode then an invocation of this
 392      * method initiates a non-blocking connection operation.  If the connection
 393      * is established immediately, as can happen with a local connection, then
 394      * this method returns {@code true}.  Otherwise this method returns
 395      * {@code false} and the connection operation must later be completed by
 396      * invoking the {@link #finishConnect finishConnect} method.
 397      *
 398      * <P> If this channel is in blocking mode then an invocation of this
 399      * method will block until the connection is established or an I/O error
 400      * occurs.
 401      *
 402      * <P> If a security manager has been installed then this method verifies
 403      * that its {@link java.lang.SecurityManager#checkConnect checkConnect}
 404      * method permits connecting to the address and port number of the given
 405      * remote peer.
 406      *
 407      * <p> This method may be invoked at any time. If a {@link #send send} or
 408      * {@link #receive receive} operation upon this channel is invoked while an
 409      * invocation of this method is in progress then that operation will first
 410      * block until this invocation is complete.  If a connection attempt is
 411      * initiated but fails, that is, if an invocation of this method throws a
 412      * checked exception, then the channel will be closed.
 413      *
 414      * @param  remote
 415      *         The remote peer to which this channel is to be connected
 416      *
 417      * @return  {@code true} if a connection was established, {@code false} if
 418      *          this channel is in non-blocking mode and the connection
 419      *          operation is in progress
 420      *
 421      * @throws  java.nio.channels.AlreadyConnectedException
 422      *          If this channel is already connected
 423      *
 424      * @throws  java.nio.channels.ConnectionPendingException
 425      *          If a non-blocking connection operation is already in progress on
 426      *          this channel
 427      *
 428      * @throws  java.nio.channels.ClosedChannelException
 429      *          If this channel is closed
 430      *
 431      * @throws  java.nio.channels.AsynchronousCloseException
 432      *          If another thread closes this channel
 433      *          while the connect operation is in progress
 434      *
 435      * @throws  java.nio.channels.ClosedByInterruptException
 436      *          If another thread interrupts the current thread
 437      *          while the connect operation is in progress, thereby
 438      *          closing the channel and setting the current thread's
 439      *          interrupt status
 440      *
 441      * @throws  java.nio.channels.UnresolvedAddressException
 442      *          If the given remote address is not fully resolved
 443      *
 444      * @throws  java.nio.channels.UnsupportedAddressTypeException
 445      *          If the type of the given remote address is not supported
 446      *
 447      * @throws  SecurityException
 448      *          If a security manager has been installed
 449      *          and it does not permit access to the given remote peer
 450      *
 451      * @throws  IOException
 452      *          If some other I/O error occurs
 453      */
 454     public abstract boolean connect(SocketAddress remote) throws IOException;
 455 
 456     /**
 457      * Connects this channel's socket.
 458      *
 459      * <P> This is a convience method and is equivalent to evaluating the
 460      * following expression:
 461      * <blockquote><pre>
 462      * setOption(SctpStandardSocketOptions.SCTP_INIT_MAXSTREAMS, SctpStandardSocketOption.InitMaxStreams.create(maxInStreams, maxOutStreams))
 463      *  .connect(remote);
 464      * </pre></blockquote>
 465      *
 466      * <P> The {@code maxOutStreams} and {@code maxInStreams} parameters
 467      * represent the maximum number of streams that the application wishes to be
 468      * able to send to and receive from. They are negotiated with the remote
 469      * peer and may be limited by the operating system.
 470      *
 471      * @param  remote
 472      *         The remote peer to which this channel is to be connected
 473      *
 474      * @param  maxOutStreams
 475      *         Must be non negative and no larger than {@code 65536}.
 476      *         {@code 0} to use the endpoints default value.
 477      *
 478      * @param  maxInStreams
 479      *         Must be non negative and no larger than {@code 65536}.
 480      *         {@code 0} to use the endpoints default value.
 481      *
 482      * @return  {@code true} if a connection was established, {@code false} if
 483      *          this channel is in non-blocking mode and the connection operation
 484      *          is in progress
 485      *
 486      * @throws  java.nio.channels.AlreadyConnectedException
 487      *          If this channel is already connected
 488      *
 489      * @throws  java.nio.channels.ConnectionPendingException
 490      *          If a non-blocking connection operation is already in progress on
 491      *          this channel
 492      *
 493      * @throws  java.nio.channels.ClosedChannelException
 494      *          If this channel is closed
 495      *
 496      * @throws  java.nio.channels.AsynchronousCloseException
 497      *          If another thread closes this channel
 498      *          while the connect operation is in progress
 499      *
 500      * @throws  java.nio.channels.ClosedByInterruptException
 501      *          If another thread interrupts the current thread
 502      *          while the connect operation is in progress, thereby
 503      *          closing the channel and setting the current thread's
 504      *          interrupt status
 505      *
 506      * @throws  java.nio.channels.UnresolvedAddressException
 507      *          If the given remote address is not fully resolved
 508      *
 509      * @throws  java.nio.channels.UnsupportedAddressTypeException
 510      *          If the type of the given remote address is not supported
 511      *
 512      * @throws  SecurityException
 513      *          If a security manager has been installed
 514      *          and it does not permit access to the given remote peer
 515      *
 516      * @throws  IOException
 517      *          If some other I/O error occurs
 518      */
 519     public abstract boolean connect(SocketAddress remote,
 520                                     int maxOutStreams,
 521                                     int maxInStreams)
 522         throws IOException;
 523 
 524     /**
 525      * Tells whether or not a connection operation is in progress on this channel.
 526      *
 527      * @return  {@code true} if, and only if, a connection operation has been initiated
 528      *          on this channel but not yet completed by invoking the
 529      *          {@link #finishConnect} method
 530      */
 531     public abstract boolean isConnectionPending();
 532 
 533     /**
 534      * Finishes the process of connecting an SCTP channel.
 535      *
 536      * <P> A non-blocking connection operation is initiated by placing a socket
 537      * channel in non-blocking mode and then invoking one of its {@link #connect
 538      * connect} methods.  Once the connection is established, or the attempt has
 539      * failed, the channel will become connectable and this method may
 540      * be invoked to complete the connection sequence.  If the connection
 541      * operation failed then invoking this method will cause an appropriate
 542      * {@link java.io.IOException} to be thrown.
 543      *
 544      * <P> If this channel is already connected then this method will not block
 545      * and will immediately return {@code true}.  If this channel is in
 546      * non-blocking mode then this method will return {@code false} if the
 547      * connection process is not yet complete.  If this channel is in blocking
 548      * mode then this method will block until the connection either completes
 549      * or fails, and will always either return {@code true} or throw a checked
 550      * exception describing the failure.
 551      *
 552      * <P> This method may be invoked at any time. If a {@link #send send} or {@link #receive receive}
 553      * operation upon this channel is invoked while an invocation of this
 554      * method is in progress then that operation will first block until this
 555      * invocation is complete.  If a connection attempt fails, that is, if an
 556      * invocation of this method throws a checked exception, then the channel
 557      * will be closed.
 558      *
 559      * @return  {@code true} if, and only if, this channel's socket is now
 560      *          connected
 561      *
 562      * @throws  java.nio.channels.NoConnectionPendingException
 563      *          If this channel is not connected and a connection operation
 564      *          has not been initiated
 565      *
 566      * @throws  java.nio.channels.ClosedChannelException
 567      *          If this channel is closed
 568      *
 569      * @throws  java.nio.channels.AsynchronousCloseException
 570      *          If another thread closes this channel
 571      *          while the connect operation is in progress
 572      *
 573      * @throws  java.nio.channels.ClosedByInterruptException
 574      *          If another thread interrupts the current thread
 575      *          while the connect operation is in progress, thereby
 576      *          closing the channel and setting the current thread's
 577      *          interrupt status
 578      *
 579      * @throws  IOException
 580      *          If some other I/O error occurs
 581      */
 582     public abstract boolean finishConnect() throws IOException;
 583 
 584     /**
 585      * Returns all of the socket addresses to which this channel's socket is
 586      * bound.
 587      *
 588      * @return  All the socket addresses that this channel's socket is
 589      *          bound to, or an empty {@code Set} if the channel's socket is not
 590      *          bound
 591      *
 592      * @throws  ClosedChannelException
 593      *          If the channel is closed
 594      *
 595      * @throws  IOException
 596      *          If an I/O error occurs
 597      */
 598     public abstract Set<SocketAddress> getAllLocalAddresses()
 599         throws IOException;
 600 
 601     /**
 602      * Returns all of the remote addresses to which this channel's socket
 603      * is connected.
 604      *
 605      * <P> If the channel is connected to a remote peer that is bound to
 606      * multiple addresses then it is these addresses that the channel's socket
 607      * is connected.
 608      *
 609      * @return  All of the remote addresses to which this channel's socket
 610      *          is connected, or an empty {@code Set} if the channel's socket is
 611      *          not connected
 612      *
 613      * @throws  ClosedChannelException
 614      *          If the channel is closed
 615      *
 616      * @throws  IOException
 617      *          If an I/O error occurs
 618      */
 619     public abstract Set<SocketAddress> getRemoteAddresses()
 620         throws IOException;
 621 
 622     /**
 623      * Shutdown a connection without closing the channel.
 624      *
 625      * <P> Sends a shutdown command to the remote peer, effectively preventing
 626      * any new data from being written to the socket by either peer. Further
 627      * sends will throw {@link java.nio.channels.ClosedChannelException}. The
 628      * channel remains open to allow the for any data (and notifications) to be
 629      * received that may have been sent by the peer before it received the
 630      * shutdown command. If the channel is already shutdown then invoking this
 631      * method has no effect.
 632      *
 633      * @return  This channel
 634      *
 635      * @throws  java.nio.channels.NotYetConnectedException
 636      *          If this channel is not yet connected
 637      *
 638      * @throws  java.nio.channels.ClosedChannelException
 639      *          If this channel is closed
 640      *
 641      * @throws  IOException
 642      *          If some other I/O error occurs
 643      */
 644     public abstract SctpChannel shutdown() throws IOException;
 645 
 646     /**
 647      * Returns the value of a socket option.
 648      *
 649      * @param   <T>
 650      *          The type of the socket option value
 651      *
 652      * @param   name
 653      *          The socket option
 654      *
 655      * @return  The value of the socket option. A value of {@code null} may be
 656      *          a valid value for some socket options.
 657      *
 658      * @throws  UnsupportedOperationException
 659      *          If the socket option is not supported by this channel
 660      *
 661      * @throws  ClosedChannelException
 662      *          If this channel is closed
 663      *
 664      * @throws  IOException
 665      *          If an I/O error occurs
 666      *
 667      * @see SctpStandardSocketOptions
 668      */
 669     public abstract <T> T getOption(SctpSocketOption<T> name)
 670         throws IOException;
 671 
 672     /**
 673      * Sets the value of a socket option.
 674      *
 675      * @param   <T>
 676      *          The type of the socket option value
 677      *
 678      * @param   name
 679      *          The socket option
 680      *
 681      * @param   value
 682      *          The value of the socket option. A value of {@code null} may be
 683      *          a valid value for some socket options.
 684      *
 685      * @return  This channel
 686      *
 687      * @throws  UnsupportedOperationException
 688      *          If the socket option is not supported by this channel
 689      *
 690      * @throws  IllegalArgumentException
 691      *          If the value is not a valid value for this socket option
 692      *
 693      * @throws  ClosedChannelException
 694      *          If this channel is closed
 695      *
 696      * @throws  IOException
 697      *          If an I/O error occurs
 698      *
 699      * @see SctpStandardSocketOptions
 700      */
 701     public abstract <T> SctpChannel setOption(SctpSocketOption<T> name, T value)
 702         throws IOException;
 703 
 704     /**
 705      * Returns a set of the socket options supported by this channel.
 706      *
 707      * <P> This method will continue to return the set of options even after the
 708      * channel has been closed.
 709      *
 710      * @return  A set of the socket options supported by this channel
 711      */
 712     public abstract Set<SctpSocketOption<?>> supportedOptions();
 713 
 714     /**
 715      * Returns an operation set identifying this channel's supported operations.
 716      *
 717      * <P> SCTP channels support connecting, reading, and writing, so this
 718      * method returns {@code (}{@link SelectionKey#OP_CONNECT}
 719      * {@code |}&nbsp;{@link SelectionKey#OP_READ} {@code |}&nbsp;{@link
 720      * SelectionKey#OP_WRITE}{@code )}.
 721      *
 722      * @return  The valid-operation set
 723      */
 724     @Override
 725     public final int validOps() {
 726         return (SelectionKey.OP_READ |
 727                 SelectionKey.OP_WRITE |
 728                 SelectionKey.OP_CONNECT);
 729     }
 730 
 731     /**
 732      * Receives a message into the given buffer and/or handles a notification.
 733      *
 734      * <P> If a message or notification is immediately available, or if this
 735      * channel is in blocking mode and one eventually becomes available, then
 736      * the message or notification is returned or handled, respectively. If this
 737      * channel is in non-blocking mode and a message or notification is not
 738      * immediately available then this method immediately returns {@code null}.
 739      *
 740      * <P> If this method receives a message it is copied into the given byte
 741      * buffer. The message is transferred into the given byte buffer starting at
 742      * its current position and the buffers position is incremented by the
 743      * number of bytes read. If there are fewer bytes remaining in the buffer
 744      * than are required to hold the message, or the underlying input buffer
 745      * does not contain the complete message, then an invocation of {@link
 746      * MessageInfo#isComplete isComplete} on the returned {@code
 747      * MessageInfo} will return {@code false}, and more invocations of this
 748      * method will be necessary to completely consume the messgae. Only
 749      * one message at a time will be partially delivered in any stream. The
 750      * socket option {@link SctpStandardSocketOptions#SCTP_FRAGMENT_INTERLEAVE
 751      * SCTP_FRAGMENT_INTERLEAVE} controls various aspects of what interlacing of
 752      * messages occurs.
 753      *
 754      * <P> If this method receives a notification then the appropriate method of
 755      * the given handler, if there is one, is invoked. If the handler returns
 756      * {@link HandlerResult#CONTINUE CONTINUE} then this method will try to
 757      * receive another message/notification, otherwise, if {@link
 758      * HandlerResult#RETURN RETURN} is returned this method will return {@code
 759      * null}. If an uncaught exception is thrown by the handler it will be
 760      * propagated up the stack through this method.
 761      *
 762      * <P> This method may be invoked at any time. If another thread has
 763      * already initiated a receive operation upon this channel, then an
 764      * invocation of this method will block until the first operation is
 765      * complete. The given handler is invoked without holding any locks used
 766      * to enforce the above synchronization policy, that way handlers
 767      * will not stall other threads from receiving. A handler should not invoke
 768      * the {@code receive} method of this channel, if it does an
 769      * {@link IllegalReceiveException} will be thrown.
 770      *
 771      * @param  <T>
 772      *         The type of the attachment
 773      *
 774      * @param  dst
 775      *         The buffer into which message bytes are to be transferred
 776      *
 777      * @param  attachment
 778      *         The object to attach to the receive operation; can be
 779      *         {@code null}
 780      *
 781      * @param  handler
 782      *         A handler to handle notifications from the SCTP stack, or {@code
 783      *         null} to ignore any notifications.
 784      *
 785      * @return  The {@code MessageInfo}, {@code null} if this channel is in
 786      *          non-blocking mode and no messages are immediately available or
 787      *          the notification handler returns {@link HandlerResult#RETURN
 788      *          RETURN} after handling a notification
 789      *
 790      * @throws  java.nio.channels.ClosedChannelException
 791      *          If this channel is closed
 792      *
 793      * @throws  java.nio.channels.AsynchronousCloseException
 794      *          If another thread closes this channel
 795      *          while the read operation is in progress
 796      *
 797      * @throws  java.nio.channels.ClosedByInterruptException
 798      *          If another thread interrupts the current thread
 799      *          while the read operation is in progress, thereby
 800      *          closing the channel and setting the current thread's
 801      *          interrupt status
 802      *
 803      * @throws  java.nio.channels.NotYetConnectedException
 804      *          If this channel is not yet connected
 805      *
 806      * @throws  IllegalReceiveException
 807      *          If the given handler invokes the {@code receive} method of this
 808      *          channel
 809      *
 810      * @throws  IOException
 811      *          If some other I/O error occurs
 812      */
 813     public abstract <T> MessageInfo receive(ByteBuffer dst,
 814                                             T attachment,
 815                                             NotificationHandler<T> handler)
 816         throws IOException;
 817 
 818     /**
 819      * Sends a message via this channel.
 820      *
 821      * <P> If this channel is in non-blocking mode and there is sufficient room
 822      * in the underlying output buffer, or if this channel is in blocking mode
 823      * and sufficient room becomes available, then the remaining bytes in the
 824      * given byte buffer are transmitted as a single message. Sending a message
 825      * is atomic unless explicit message completion {@link
 826      * SctpStandardSocketOptions#SCTP_EXPLICIT_COMPLETE SCTP_EXPLICIT_COMPLETE}
 827      * socket option is enabled on this channel's socket.
 828      *
 829      * <P> The message is transferred from the byte buffer as if by a regular
 830      * {@link java.nio.channels.WritableByteChannel#write(java.nio.ByteBuffer)
 831      * write} operation.
 832      *
 833      * <P> The bytes will be written to the stream number that is specified by
 834      * {@link MessageInfo#streamNumber streamNumber} in the given {@code
 835      * messageInfo}.
 836      *
 837      * <P> This method may be invoked at any time. If another thread has already
 838      * initiated a send operation upon this channel, then an invocation of
 839      * this method will block until the first operation is complete.
 840      *
 841      * @param  src
 842      *         The buffer containing the message to be sent
 843      *
 844      * @param  messageInfo
 845      *         Ancillary data about the message to be sent
 846      *
 847      * @return  The number of bytes sent, which will be either the number of
 848      *          bytes that were remaining in the messages buffer when this method
 849      *          was invoked or, if this channel is non-blocking, may be zero if
 850      *          there was insufficient room for the message in the underlying
 851      *          output buffer
 852      *
 853      * @throws  InvalidStreamException
 854      *          If {@code streamNumner} is negative or greater than or equal to
 855      *          the maximum number of outgoing streams
 856      *
 857      * @throws  java.nio.channels.ClosedChannelException
 858      *          If this channel is closed
 859      *
 860      * @throws  java.nio.channels.AsynchronousCloseException
 861      *          If another thread closes this channel
 862      *          while the read operation is in progress
 863      *
 864      * @throws  java.nio.channels.ClosedByInterruptException
 865      *          If another thread interrupts the current thread
 866      *          while the read operation is in progress, thereby
 867      *          closing the channel and setting the current thread's
 868      *          interrupt status
 869      *
 870      * @throws  java.nio.channels.NotYetConnectedException
 871      *          If this channel is not yet connected
 872      *
 873      * @throws  IOException
 874      *          If some other I/O error occurs
 875      */
 876     public abstract int send(ByteBuffer src, MessageInfo messageInfo)
 877         throws IOException;
 878 }