1 /*
2 * Copyright (c) 2000, 2013, 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
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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
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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> 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>Option Name</th>
74 * <th>Description</th>
75 * </tr>
76 * </thead>
77 * <tbody>
78 * <tr>
79 * <td> {@link java.net.StandardSocketOptions#SO_SNDBUF SO_SNDBUF} </td>
80 * <td> The size of the socket send buffer </td>
81 * </tr>
82 * <tr>
83 * <td> {@link java.net.StandardSocketOptions#SO_RCVBUF SO_RCVBUF} </td>
84 * <td> The size of the socket receive buffer </td>
85 * </tr>
86 * <tr>
87 * <td> {@link java.net.StandardSocketOptions#SO_KEEPALIVE SO_KEEPALIVE} </td>
88 * <td> Keep connection alive </td>
89 * </tr>
90 * <tr>
91 * <td> {@link java.net.StandardSocketOptions#SO_REUSEADDR SO_REUSEADDR} </td>
92 * <td> Re-use address </td>
93 * </tr>
94 * <tr>
95 * <td> {@link java.net.StandardSocketOptions#SO_LINGER SO_LINGER} </td>
96 * <td> Linger on close if data is present (when configured in blocking mode
97 * only) </td>
98 * </tr>
99 * <tr>
100 * <td> {@link java.net.StandardSocketOptions#TCP_NODELAY TCP_NODELAY} </td>
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 }