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3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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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 <tt>-1</tt>.  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 border summary="Socket options">
70   *   <tr>
71   *     <th>Option Name</th>
72   *     <th>Description</th>
73   *   </tr>
74   *   <tr>
75   *     <td> {@link java.net.StandardSocketOptions#SO_SNDBUF SO_SNDBUF} </td>
76   *     <td> The size of the socket send buffer </td>
77   *   </tr>
78   *   <tr>
79   *     <td> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </td>
80   *     <td> The size of the socket receive buffer </td>
81   *   </tr>
82   *   <tr>
83   *     <td> {@link java.net.StandardSocketOptions#SO_KEEPALIVE SO_KEEPALIVE} </td>
84   *     <td> Keep connection alive </td>
85   *   </tr>
86   *   <tr>
87   *     <td> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </td>
88   *     <td> Re-use address </td>
89   *   </tr>
90   *   <tr>
91   *     <td> {@link java.net.StandardSocketOptions#SO_LINGER SO_LINGER} </td>
92   *     <td> Linger on close if data is present (when configured in blocking mode
93   *          only) </td>
94   *   </tr>
95   *   <tr>
96   *     <td> {@link java.net.StandardSocketOptions#TCP_NODELAY TCP_NODELAY} </td>
97   *     <td> Disable the Nagle algorithm </td>
98   *   </tr>
99   * </table>
100  * </blockquote>
101  * Additional (implementation specific) options may also be supported.
102  *
103  * <p> Socket channels are safe for use by multiple concurrent threads.  They
104  * support concurrent reading and writing, though at most one thread may be
105  * reading and at most one thread may be writing at any given time.  The {@link
106  * #connect connect} and {@link #finishConnect finishConnect} methods are
107  * mutually synchronized against each other, and an attempt to initiate a read
108  * or write operation while an invocation of one of these methods is in
109  * progress will block until that invocation is complete.  </p>
110  *
111  * @author Mark Reinhold
112  * @author JSR-51 Expert Group
113  * @since 1.4
114  */
115 
116 public abstract class SocketChannel
117     extends AbstractSelectableChannel
118     implements ByteChannel, ScatteringByteChannel, GatheringByteChannel, NetworkChannel
119 {
120 
121     /**
122      * Initializes a new instance of this class.
123      *
124      * @param  provider
125      *         The provider that created this channel
126      */
127     protected SocketChannel(SelectorProvider provider) {
128         super(provider);
129     }
130 
131     /**
132      * Opens a socket channel.
133      *
134      * <p> The new channel is created by invoking the {@link
135      * java.nio.channels.spi.SelectorProvider#openSocketChannel
136      * openSocketChannel} method of the system-wide default {@link
137      * java.nio.channels.spi.SelectorProvider} object.  </p>
138      *
139      * @return  A new socket channel
140      *
141      * @throws  IOException
142      *          If an I/O error occurs
143      */
144     public static SocketChannel open() throws IOException {
145         return SelectorProvider.provider().openSocketChannel();
146     }
147 
148     /**
149      * Opens a socket channel and connects it to a remote address.
150      *
151      * <p> This convenience method works as if by invoking the {@link #open()}
152      * method, invoking the {@link #connect(SocketAddress) connect} method upon
153      * the resulting socket channel, passing it <tt>remote</tt>, and then
154      * returning that channel.  </p>
155      *
156      * @param  remote
157      *         The remote address to which the new channel is to be connected
158      *
159      * @return  A new, and connected, socket channel
160      *
161      * @throws  AsynchronousCloseException
162      *          If another thread closes this channel
163      *          while the connect operation is in progress
164      *
165      * @throws  ClosedByInterruptException
166      *          If another thread interrupts the current thread
167      *          while the connect operation is in progress, thereby
168      *          closing the channel and setting the current thread's
169      *          interrupt status
170      *
171      * @throws  UnresolvedAddressException
172      *          If the given remote address is not fully resolved
173      *
174      * @throws  UnsupportedAddressTypeException
175      *          If the type of the given remote address is not supported
176      *
177      * @throws  SecurityException
178      *          If a security manager has been installed
179      *          and it does not permit access to the given remote endpoint
180      *
181      * @throws  IOException
182      *          If some other I/O error occurs
183      */
184     public static SocketChannel open(SocketAddress remote)
185         throws IOException
186     {
187         SocketChannel sc = open();
188         try {
189             sc.connect(remote);
190         } catch (Throwable x) {
191             try {
192                 sc.close();
193             } catch (Throwable suppressed) {
194                 x.addSuppressed(suppressed);
195             }
196             throw x;
197         }
198         assert sc.isConnected();
199         return sc;
200     }
201 
202     /**
203      * Returns an operation set identifying this channel's supported
204      * operations.
205      *
206      * <p> Socket channels support connecting, reading, and writing, so this
207      * method returns <tt>(</tt>{@link SelectionKey#OP_CONNECT}
208      * <tt>|</tt>&nbsp;{@link SelectionKey#OP_READ} <tt>|</tt>&nbsp;{@link
209      * SelectionKey#OP_WRITE}<tt>)</tt>.  </p>
210      *
211      * @return  The valid-operation set
212      */
213     public final int validOps() {
214         return (SelectionKey.OP_READ
215                 | SelectionKey.OP_WRITE
216                 | SelectionKey.OP_CONNECT);
217     }
218 
219 
220     // -- Socket-specific operations --
221 
222     /**
223      * @throws  ConnectionPendingException
224      *          If a non-blocking connect operation is already in progress on
225      *          this channel
226      * @throws  AlreadyBoundException               {@inheritDoc}
227      * @throws  UnsupportedAddressTypeException     {@inheritDoc}
228      * @throws  ClosedChannelException              {@inheritDoc}
229      * @throws  IOException                         {@inheritDoc}
230      * @throws  SecurityException
231      *          If a security manager has been installed and its
232      *          {@link SecurityManager#checkListen checkListen} method denies
233      *          the operation
234      *
235      * @since 1.7
236      */
237     @Override
238     public abstract SocketChannel bind(SocketAddress local)
239         throws IOException;
240 
241     /**
242      * @throws  UnsupportedOperationException           {@inheritDoc}
243      * @throws  IllegalArgumentException                {@inheritDoc}
244      * @throws  ClosedChannelException                  {@inheritDoc}
245      * @throws  IOException                             {@inheritDoc}
246      *
247      * @since 1.7
248      */
249     @Override
250     public abstract <T> SocketChannel setOption(SocketOption<T> name, T value)
251         throws IOException;
252 
253     /**
254      * Shutdown the connection for reading without closing the channel.
255      *
256      * <p> Once shutdown for reading then further reads on the channel will
257      * return {@code -1}, the end-of-stream indication. If the input side of the
258      * connection is already shutdown then invoking this method has no effect.
259      *
260      * @return  The channel
261      *
262      * @throws  NotYetConnectedException
263      *          If this channel is not yet connected
264      * @throws  ClosedChannelException
265      *          If this channel is closed
266      * @throws  IOException
267      *          If some other I/O error occurs
268      *
269      * @since 1.7
270      */
271     public abstract SocketChannel shutdownInput() throws IOException;
272 
273     /**
274      * Shutdown the connection for writing without closing the channel.
275      *
276      * <p> Once shutdown for writing then further attempts to write to the
277      * channel will throw {@link ClosedChannelException}. If the output side of
278      * the connection is already shutdown then invoking this method has no
279      * effect.
280      *
281      * @return  The channel
282      *
283      * @throws  NotYetConnectedException
284      *          If this channel is not yet connected
285      * @throws  ClosedChannelException
286      *          If this channel is closed
287      * @throws  IOException
288      *          If some other I/O error occurs
289      *
290      * @since 1.7
291      */
292     public abstract SocketChannel shutdownOutput() throws IOException;
293 
294     /**
295      * Retrieves a socket associated with this channel.
296      *
297      * <p> The returned object will not declare any public methods that are not
298      * declared in the {@link java.net.Socket} class.  </p>
299      *
300      * @return  A socket associated with this channel
301      */
302     public abstract Socket socket();
303 
304     /**
305      * Tells whether or not this channel's network socket is connected.
306      *
307      * @return  <tt>true</tt> if, and only if, this channel's network socket
308      *          is {@link #isOpen open} and connected
309      */
310     public abstract boolean isConnected();
311 
312     /**
313      * Tells whether or not a connection operation is in progress on this
314      * channel.
315      *
316      * @return  <tt>true</tt> if, and only if, a connection operation has been
317      *          initiated on this channel but not yet completed by invoking the
318      *          {@link #finishConnect finishConnect} method
319      */
320     public abstract boolean isConnectionPending();
321 
322     /**
323      * Connects this channel's socket.
324      *
325      * <p> If this channel is in non-blocking mode then an invocation of this
326      * method initiates a non-blocking connection operation.  If the connection
327      * is established immediately, as can happen with a local connection, then
328      * this method returns <tt>true</tt>.  Otherwise this method returns
329      * <tt>false</tt> and the connection operation must later be completed by
330      * invoking the {@link #finishConnect finishConnect} method.
331      *
332      * <p> If this channel is in blocking mode then an invocation of this
333      * method will block until the connection is established or an I/O error
334      * occurs.
335      *
336      * <p> This method performs exactly the same security checks as the {@link
337      * java.net.Socket} class.  That is, if a security manager has been
338      * installed then this method verifies that its {@link
339      * java.lang.SecurityManager#checkConnect checkConnect} method permits
340      * connecting to the address and port number of the given remote endpoint.
341      *
342      * <p> This method may be invoked at any time.  If a read or write
343      * operation upon this channel is invoked while an invocation of this
344      * method is in progress then that operation will first block until this
345      * invocation is complete.  If a connection attempt is initiated but fails,
346      * that is, if an invocation of this method throws a checked exception,
347      * then the channel will be closed.  </p>
348      *
349      * @param  remote
350      *         The remote address to which this channel is to be connected
351      *
352      * @return  <tt>true</tt> if a connection was established,
353      *          <tt>false</tt> if this channel is in non-blocking mode
354      *          and the connection operation is in progress
355      *
356      * @throws  AlreadyConnectedException
357      *          If this channel is already connected
358      *
359      * @throws  ConnectionPendingException
360      *          If a non-blocking connection operation is already in progress
361      *          on this channel
362      *
363      * @throws  ClosedChannelException
364      *          If this channel is closed
365      *
366      * @throws  AsynchronousCloseException
367      *          If another thread closes this channel
368      *          while the connect operation is in progress
369      *
370      * @throws  ClosedByInterruptException
371      *          If another thread interrupts the current thread
372      *          while the connect operation is in progress, thereby
373      *          closing the channel and setting the current thread's
374      *          interrupt status
375      *
376      * @throws  UnresolvedAddressException
377      *          If the given remote address is not fully resolved
378      *
379      * @throws  UnsupportedAddressTypeException
380      *          If the type of the given remote address is not supported
381      *
382      * @throws  SecurityException
383      *          If a security manager has been installed
384      *          and it does not permit access to the given remote endpoint
385      *
386      * @throws  IOException
387      *          If some other I/O error occurs
388      */
389     public abstract boolean connect(SocketAddress remote) throws IOException;
390 
391     /**
392      * Finishes the process of connecting a socket channel.
393      *
394      * <p> A non-blocking connection operation is initiated by placing a socket
395      * channel in non-blocking mode and then invoking its {@link #connect
396      * connect} method.  Once the connection is established, or the attempt has
397      * failed, the socket channel will become connectable and this method may
398      * be invoked to complete the connection sequence.  If the connection
399      * operation failed then invoking this method will cause an appropriate
400      * {@link java.io.IOException} to be thrown.
401      *
402      * <p> If this channel is already connected then this method will not block
403      * and will immediately return <tt>true</tt>.  If this channel is in
404      * non-blocking mode then this method will return <tt>false</tt> if the
405      * connection process is not yet complete.  If this channel is in blocking
406      * mode then this method will block until the connection either completes
407      * or fails, and will always either return <tt>true</tt> or throw a checked
408      * exception describing the failure.
409      *
410      * <p> This method may be invoked at any time.  If a read or write
411      * operation upon this channel is invoked while an invocation of this
412      * method is in progress then that operation will first block until this
413      * invocation is complete.  If a connection attempt fails, that is, if an
414      * invocation of this method throws a checked exception, then the channel
415      * will be closed.  </p>
416      *
417      * @return  <tt>true</tt> if, and only if, this channel's socket is now
418      *          connected
419      *
420      * @throws  NoConnectionPendingException
421      *          If this channel is not connected and a connection operation
422      *          has not been initiated
423      *
424      * @throws  ClosedChannelException
425      *          If this channel is closed
426      *
427      * @throws  AsynchronousCloseException
428      *          If another thread closes this channel
429      *          while the connect operation is in progress
430      *
431      * @throws  ClosedByInterruptException
432      *          If another thread interrupts the current thread
433      *          while the connect operation is in progress, thereby
434      *          closing the channel and setting the current thread's
435      *          interrupt status
436      *
437      * @throws  IOException
438      *          If some other I/O error occurs
439      */
440     public abstract boolean finishConnect() throws IOException;
441 
442     /**
443      * Returns the remote address to which this channel's socket is connected.
444      *
445      * <p> Where the channel is bound and connected to an Internet Protocol
446      * socket address then the return value from this method is of type {@link
447      * java.net.InetSocketAddress}.
448      *
449      * @return  The remote address; {@code null} if the channel's socket is not
450      *          connected
451      *
452      * @throws  ClosedChannelException
453      *          If the channel is closed
454      * @throws  IOException
455      *          If an I/O error occurs
456      *
457      * @since 1.7
458      */
459     public abstract SocketAddress getRemoteAddress() throws IOException;
460 
461     // -- ByteChannel operations --
462 
463     /**
464      * @throws  NotYetConnectedException
465      *          If this channel is not yet connected
466      */
467     public abstract int read(ByteBuffer dst) throws IOException;
468 
469     /**
470      * @throws  NotYetConnectedException
471      *          If this channel is not yet connected
472      */
473     public abstract long read(ByteBuffer[] dsts, int offset, int length)
474         throws IOException;
475 
476     /**
477      * @throws  NotYetConnectedException
478      *          If this channel is not yet connected
479      */
480     public final long read(ByteBuffer[] dsts) throws IOException {
481         return read(dsts, 0, dsts.length);
482     }
483 
484     /**
485      * @throws  NotYetConnectedException
486      *          If this channel is not yet connected
487      */
488     public abstract int write(ByteBuffer src) throws IOException;
489 
490     /**
491      * @throws  NotYetConnectedException
492      *          If this channel is not yet connected
493      */
494     public abstract long write(ByteBuffer[] srcs, int offset, int length)
495         throws IOException;
496 
497     /**
498      * @throws  NotYetConnectedException
499      *          If this channel is not yet connected
500      */
501     public final long write(ByteBuffer[] srcs) throws IOException {
502         return write(srcs, 0, srcs.length);
503     }
504 
505     /**
506      * {@inheritDoc}
507      * <p>
508      * If there is a security manager set, its {@code checkConnect} method is
509      * called with the local address and {@code -1} as its arguments to see
510      * if the operation is allowed. If the operation is not allowed,
511      * a {@code SocketAddress} representing the
512      * {@link java.net.InetAddress#getLoopbackAddress loopback} address and the
513      * local port of the channel's socket is returned.
514      *
515      * @return  The {@code SocketAddress} that the socket is bound to, or the
516      *          {@code SocketAddress} representing the loopback address if
517      *          denied by the security manager, or {@code null} if the
518      *          channel's socket is not bound
519      *
520      * @throws  ClosedChannelException     {@inheritDoc}
521      * @throws  IOException                {@inheritDoc}
522      */
523     @Override
524     public abstract SocketAddress getLocalAddress() throws IOException;
525 
526 }