/*
* Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package jdk.incubator.http;
import java.io.IOException;
import java.net.ProtocolException;
import java.net.URI;
import java.nio.ByteBuffer;
import java.time.Duration;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
/**
* A WebSocket client conforming to RFC 6455.
* {@Incubating}
*
* <p> A {@code WebSocket} provides full-duplex communication over a TCP
* connection.
*
* <p> To create a {@code WebSocket} use a {@linkplain HttpClient#newWebSocketBuilder(
* URI, Listener) builder}. Once a {@code WebSocket} is built, it's ready
* to send and receive messages. When the {@code WebSocket} is no longer needed
* it must be closed: a Close message must both be {@linkplain #sendClose
* sent} and {@linkplain Listener#onClose(WebSocket, int, String) received}.
* The {@code WebSocket} may be also closed {@linkplain #abort() abruptly}.
*
* <p> Once closed the {@code WebSocket} remains {@linkplain #isClosed() closed}
* and cannot be reopened.
*
* <p> Messages of type {@code X} (where {@code X} is one of: Text, Binary,
* Ping, Pong or Close) are sent and received asynchronously through the {@code
* WebSocket.send{X}} and {@link WebSocket.Listener}{@code .on{X}} methods
* respectively. Each method returns a {@link CompletionStage} which completes
* when the operation has completed.
*
* <p> Note that messages (of any type) are received only if {@linkplain
* #request(long) requested}.
*
* <p> One outstanding send operation is permitted. No further send operation
* can be initiated before the previous one has completed. When sending, a
* message must not be modified until the returned {@link CompletableFuture}
* completes (either normally or exceptionally).
*
* <p> Text and Binary messages can be sent and received as a whole or in parts.
* A whole message is transferred as a sequence of one or more invocations of a
* corresponding method where the last invocation is identified via an
* additional method argument.
*
* <p> If the message is contained in a {@link ByteBuffer}, bytes are considered
* arranged from the {@code buffer}'s {@link ByteBuffer#position() position} to
* the {@code buffer}'s {@link ByteBuffer#limit() limit}.
*
* <p> Unless otherwise stated, {@code null} parameter values will cause methods
* and constructors to throw {@link NullPointerException}.
*
* @implNote This implementation's methods do not block before returning
* a {@code CompletableFuture}.
*
* @since 9
*/
public interface WebSocket {
/**
* The WebSocket Close message status code (<code>{@value}</code>),
* indicating normal closure, meaning that the purpose for which the
* connection was established has been fulfilled.
*
* @see #sendClose(int, String)
* @see Listener#onClose(WebSocket, int, String)
*/
int NORMAL_CLOSURE = 1000;
/**
* A builder for creating {@code WebSocket} instances.
* {@Incubating}
*
* <p> To build a {@code WebSocket}, {@linkplain HttpClient#newWebSocketBuilder(
* URI, Listener) create} a builder, configure it as required by
* calling intermediate methods (the ones that return the builder itself),
* then finally call {@link #buildAsync()} to get a {@link
* CompletableFuture} with resulting {@code WebSocket}.
*
* <p> If an intermediate method has not been called, an appropriate
* default value (or behavior) will be used. Unless otherwise noted, a
* repeated call to an intermediate method overwrites the previous value (or
* overrides the previous behaviour).
*
* <p> Instances of {@code Builder} are not safe for use by multiple threads
* without external synchronization.
*
* @since 9
*/
interface Builder {
/**
* Adds the given name-value pair to the list of additional headers for
* the opening handshake.
*
* <p> Headers defined in WebSocket Protocol are not allowed to be added.
*
* @param name
* the header name
* @param value
* the header value
*
* @return this builder
*/
Builder header(String name, String value);
/**
* Includes a request for the given subprotocols during the opening
* handshake.
*
* <p> Among the requested subprotocols at most one will be chosen by
* the server. This subprotocol will be available from {@link
* WebSocket#getSubprotocol}. Subprotocols are specified in the order of
* preference.
*
* <p> Each of the given subprotocols must conform to the relevant
* rules defined in the WebSocket Protocol.
*
* <p> If this method is not invoked then no subprotocols are requested.
*
* @param mostPreferred
* the most preferred subprotocol
* @param lesserPreferred
* the lesser preferred subprotocols, with the least preferred
* at the end
*
* @return this builder
*/
Builder subprotocols(String mostPreferred, String... lesserPreferred);
/**
* Sets a timeout for the opening handshake.
*
* <p> If the opening handshake does not complete within the specified
* duration then the {@code CompletableFuture} returned from {@link
* #buildAsync()} completes exceptionally with a {@link
* HttpTimeoutException}.
*
* <p> If this method is not invoked then the timeout is deemed infinite.
*
* @param timeout
* the timeout, non-{@linkplain Duration#isNegative() negative},
* non-{@linkplain Duration#ZERO ZERO}
*
* @return this builder
*/
Builder connectTimeout(Duration timeout);
/**
* Builds a {@code WebSocket}.
*
* <p> Returns a {@code CompletableFuture<WebSocket>} which completes
* normally with the {@code WebSocket} when it is connected or completes
* exceptionally if an error occurs.
*
* <p> {@code CompletableFuture} may complete exceptionally with the
* following errors:
* <ul>
* <li> {@link IOException} -
* if an I/O error occurs
* <li> {@link WebSocketHandshakeException} -
* if the opening handshake fails
* <li> {@link HttpTimeoutException} -
* if the opening handshake does not complete within
* the specified {@linkplain #connectTimeout(Duration) duration}
* <li> {@link InterruptedException} -
* if the operation was interrupted
* <li> {@link SecurityException} -
* If a security manager has been installed and it denies
* {@link java.net.URLPermission access} to the WebSocket URI,
* that was used to create this builder.
* <a href="HttpRequest.html#securitychecks">Security checks</a>
* contains more information relating to the security context
* in which the the listener is invoked.
* <li> {@link IllegalArgumentException} -
* if any of the additional {@link #header(String, String)
* headers} are illegal;
* or if any of the WebSocket Protocol rules relevant to {@link
* #subprotocols(String, String...) subprotocols} are violated;
* or if the {@link #connectTimeout(Duration) connect timeout}
* is invalid;
* </ul>
*
* @return a {@code CompletableFuture} with the {@code WebSocket}
*/
CompletableFuture<WebSocket> buildAsync();
}
/**
* A listener for events and messages on a {@code WebSocket}.
* {@Incubating}
*
* <p> Each method of {@code Listener} corresponds to a type of event or a
* type of message. The {@code WebSocket} argument of the method is the
* {@code WebSocket} the event has occurred (the message has been received)
* on. All methods with the same {@code WebSocket} argument are invoked in a
* sequential
* (and <a href="../../../java/util/concurrent/package-summary.html#MemoryVisibility">happens-before</a>)
* order, one after another, possibly by different threads.
*
* <ul>
* <li> {@link #onOpen(WebSocket) onOpen} <br>
* This method is invoked first.
* <li> {@link #onText(WebSocket, CharSequence, WebSocket.MessagePart)
* onText}, {@link #onBinary(WebSocket, ByteBuffer, WebSocket.MessagePart)
* onBinary}, {@link #onPing(WebSocket, ByteBuffer) onPing} and {@link
* #onPong(WebSocket, ByteBuffer) onPong} <br>
* These methods are invoked zero or more times after {@code onOpen}.
* <li> {@link #onClose(WebSocket, int, String) onClose}, {@link
* #onError(WebSocket, Throwable) onError} <br>
* Only one of these methods is invoked, and that method is invoked last.
* </ul>
*
* <p> Messages received by the {@code Listener} conform to the WebSocket
* Protocol, otherwise {@code onError} with a {@link ProtocolException} is
* invoked.
*
* <p> If a whole message is received, then the corresponding method
* ({@code onText} or {@code onBinary}) will be invoked with {@link
* WebSocket.MessagePart#WHOLE WHOLE} marker. Otherwise the method will be
* invoked with {@link WebSocket.MessagePart#FIRST FIRST}, zero or more
* times with {@link WebSocket.MessagePart#PART PART} and, finally, with
* {@link WebSocket.MessagePart#LAST LAST} markers.
*
* If any of the methods above throws an exception, {@code onError} is then
* invoked with the same {@code WebSocket} and this exception. Exceptions
* thrown from {@code onError} or {@code onClose} are ignored.
*
* <p> When the method returns, the message is deemed received (in
* particular, if contained in a {@code ByteBuffer buffer}, the data is
* deemed received completely regardless of the result {@code
* buffer.hasRemaining()} upon the method's return. After this further
* messages may be received.
*
* <p> These invocations begin asynchronous processing which might not end
* with the invocation. To provide coordination, methods of {@code Listener}
* return a {@link CompletionStage CompletionStage}.
* The {@code CompletionStage} signals the {@code WebSocket} that the
* processing of a message has ended. For convenience, methods may return
* {@code null}, which (by convention) means the same as returning an
* already completed (normally) {@code CompletionStage}.
* If the returned {@code CompletionStage} completes exceptionally, then
* {@link #onError(WebSocket, Throwable) onError} will be invoked with the
* same {@code WebSocket} and this exception.
*
* <p> Control of the message passes to the {@code Listener} with the
* invocation of the method. Control of the message returns to the {@code
* WebSocket} at the earliest of, either returning {@code null} from the
* method, or the completion of the {@code CompletionStage} returned from
* the method. The {@code WebSocket} does not access the message while it's
* not in its control. The {@code Listener} must not access the message
* after its control has been returned to the {@code WebSocket}.
*
* <p> A {@code WebSocket} implementation never invokes {@code Listener}'s
* methods with {@code null}s as their arguments.
*
* @since 9
*/
interface Listener {
/**
* Notifies the {@code Listener} that it is connected to the provided
* {@code WebSocket}.
*
* <p> The {@code onOpen} method does not correspond to any message from
* the WebSocket Protocol. It is a synthetic event and the first {@code
* Listener}'s method to be invoked.
*
* <p> This method is usually used to make an initial {@linkplain
* WebSocket#request(long) request} for messages.
*
* <p> If an exception is thrown from this method then {@link
* #onError(WebSocket, Throwable) onError} will be invoked with the same
* {@code WebSocket} and this exception.
*
* @implSpec The default implementation of this method behaves as if:
*
* <pre>{@code
* webSocket.request(1);
* }</pre>
*
* @param webSocket
* the WebSocket
*/
default void onOpen(WebSocket webSocket) { webSocket.request(1); }
/**
* Receives a Text message.
*
* <p> The {@code onText} method is invoked zero or more times between
* {@code onOpen} and ({@code onClose} or {@code onError}).
*
* <p> This message may be a partial UTF-16 sequence. However, the
* concatenation of all messages through the last will be a whole UTF-16
* sequence.
*
* <p> If an exception is thrown from this method or the returned {@code
* CompletionStage} completes exceptionally, then {@link
* #onError(WebSocket, Throwable) onError} will be invoked with the same
* {@code WebSocket} and this exception.
*
* @implSpec The default implementation of this method behaves as if:
*
* <pre>{@code
* webSocket.request(1);
* return null;
* }</pre>
*
* @implNote This implementation passes only complete UTF-16 sequences
* to the {@code onText} method.
*
* @param webSocket
* the WebSocket
* @param message
* the message
* @param part
* the part
*
* @return a {@code CompletionStage} which completes when the message
* processing is done; or {@code null} if already done
*/
default CompletionStage<?> onText(WebSocket webSocket,
CharSequence message,
MessagePart part) {
webSocket.request(1);
return null;
}
/**
* Receives a Binary message.
*
* <p> The {@code onBinary} method is invoked zero or more times
* between {@code onOpen} and ({@code onClose} or {@code onError}).
*
* <p> If an exception is thrown from this method or the returned {@code
* CompletionStage} completes exceptionally, then {@link
* #onError(WebSocket, Throwable) onError} will be invoked with the same
* {@code WebSocket} and this exception.
*
* @implSpec The default implementation of this method behaves as if:
*
* <pre>{@code
* webSocket.request(1);
* return null;
* }</pre>
*
* @param webSocket
* the WebSocket
* @param message
* the message
* @param part
* the part
*
* @return a {@code CompletionStage} which completes when the message
* processing is done; or {@code null} if already done
*/
default CompletionStage<?> onBinary(WebSocket webSocket,
ByteBuffer message,
MessagePart part) {
webSocket.request(1);
return null;
}
/**
* Receives a Ping message.
*
* <p> A Ping message may be sent or received by either client or
* server. It may serve either as a keepalive or as a means to verify
* that the remote endpoint is still responsive.
*
* <p> The {@code WebSocket} handles Ping messages by replying with
* appropriate Pong messages using a strategy of its choice, but within
* the boundaries of the WebSocket Protocol. The {@code WebSocket} may
* invoke {@code onPing} after handling a Ping message, before doing so
* or in parallel with it. In other words no particular ordering is
* guaranteed. If an error occurs while implementation handles this Ping
* message, then {@code onError} will be invoked with this error. For
* more details on handling Ping messages see RFC 6455 sections
* <a href="https://tools.ietf.org/html/rfc6455#section-5.5.2">5.5.2. Ping</a>
* and
* <a href="https://tools.ietf.org/html/rfc6455#section-5.5.3">5.5.3. Pong</a>.
*
* <p> The message will consist of not more than {@code 125} bytes:
* {@code message.remaining() <= 125}.
*
* <p> The {@code onPing} is invoked zero or more times in between
* {@code onOpen} and ({@code onClose} or {@code onError}).
*
* <p> If an exception is thrown from this method or the returned {@code
* CompletionStage} completes exceptionally, then {@link
* #onError(WebSocket, Throwable) onError} will be invoked with this
* exception.
*
* @implSpec The default implementation of this method behaves as if:
*
* <pre>{@code
* webSocket.request(1);
* return null;
* }</pre>
*
* @param webSocket
* the WebSocket
* @param message
* the message
*
* @return a {@code CompletionStage} which completes when the message
* processing is done; or {@code null} if already done
*/
default CompletionStage<?> onPing(WebSocket webSocket,
ByteBuffer message) {
webSocket.request(1);
return null;
}
/**
* Receives a Pong message.
*
* <p> A Pong message may be unsolicited or may be received in response
* to a previously sent Ping. In the latter case, the contents of the
* Pong is identical to the originating Ping.
*
* <p> The message will consist of not more than {@code 125} bytes:
* {@code message.remaining() <= 125}.
*
* <p> The {@code onPong} method is invoked zero or more times in
* between {@code onOpen} and ({@code onClose} or {@code onError}).
*
* <p> If an exception is thrown from this method or the returned {@code
* CompletionStage} completes exceptionally, then {@link
* #onError(WebSocket, Throwable) onError} will be invoked with this
* exception.
*
* @implSpec The default implementation of this method behaves as if:
*
* <pre>{@code
* webSocket.request(1);
* return null;
* }</pre>
*
* @param webSocket
* the WebSocket
* @param message
* the message
*
* @return a {@code CompletionStage} which completes when the message
* processing is done; or {@code null} if already done
*/
default CompletionStage<?> onPong(WebSocket webSocket,
ByteBuffer message) {
webSocket.request(1);
return null;
}
/**
* Receives a Close message.
*
* <p> A Close message consists of a status code and a reason for
* closing. The status code is an integer in the range {@code 1000 <=
* code <= 65535}. The {@code reason} is a short string that has an
* UTF-8 representation not longer than {@code 123} bytes. For more
* details on Close message, status codes and reason see RFC 6455 sections
* <a href="https://tools.ietf.org/html/rfc6455#section-5.5.1">5.5.1. Close</a>
* and
* <a href="https://tools.ietf.org/html/rfc6455#section-7.4">7.4. Status Codes</a>.
*
* <p> After the returned {@code CompletionStage} has completed
* (normally or exceptionally), the {@code WebSocket} completes the
* closing handshake by replying with an appropriate Close message.
*
* <p> This implementation replies with a Close message that has the
* same code this message has and an empty reason.
*
* <p> {@code onClose} is the last invocation on the {@code Listener}.
* It is invoked at most once, but after {@code onOpen}. If an exception
* is thrown from this method, it is ignored.
*
* <p> The {@code WebSocket} will close at the earliest of completion of
* the returned {@code CompletionStage} or sending a Close message. In
* particular, if a Close message has been {@linkplain WebSocket#sendClose
* sent} before, then this invocation completes the closing handshake
* and by the time this method is invoked, the {@code WebSocket} will
* have been closed.
*
* @implSpec The default implementation of this method behaves as if:
*
* <pre>{@code
* return null;
* }</pre>
*
* @param webSocket
* the WebSocket
* @param statusCode
* the status code
* @param reason
* the reason
*
* @return a {@code CompletionStage} which completes when the {@code
* WebSocket} can be closed; or {@code null} if it can be closed immediately
*
* @see #NORMAL_CLOSURE
*/
default CompletionStage<?> onClose(WebSocket webSocket,
int statusCode,
String reason) {
return null;
}
/**
* Notifies an I/O or protocol error has occurred.
*
* <p> The {@code onError} method does not correspond to any message
* from the WebSocket Protocol. It is a synthetic event and the last
* {@code Listener}'s method to be invoked. It is invoked at most once
* but after {@code onOpen}. If an exception is thrown from this method,
* it is ignored.
*
* <p> Note that the WebSocket Protocol requires <i>some</i> errors
* occur in the incoming destination must be fatal to the connection. In
* such cases the implementation takes care of <i>Failing the WebSocket
* Connection</i>: by the time {@code onError} is invoked, the {@code
* WebSocket} will have been closed. Any outstanding or subsequent send
* operation will complete exceptionally with an {@code IOException}.
* For more details on Failing the WebSocket Connection see RFC 6455
* section <a href="https://tools.ietf.org/html/rfc6455#section-7.1.7">7.1.7. Fail the WebSocket Connection</a>.
*
* @apiNote Errors associated with sending messages are reported to the
* {@code CompletableFuture}s {@code sendX} methods return, rather than
* to this this method.
*
* @implSpec The default implementation of this method does nothing.
*
* @param webSocket
* the WebSocket
* @param error
* the error
*/
default void onError(WebSocket webSocket, Throwable error) { }
}
/**
* A marker used by {@link WebSocket.Listener} in cases where a partial
* message may be received.
* {@Incubating}
*
* @see Listener#onText(WebSocket, CharSequence, MessagePart)
* @see Listener#onBinary(WebSocket, ByteBuffer, MessagePart)
*
* @since 9
*/
enum MessagePart {
/**
* The first part of a message in a sequence.
*/
FIRST,
/**
* A middle part of a message in a sequence.
*/
PART,
/**
* The last part of a message in a sequence.
*/
LAST,
/**
* A whole message consisting of a single part.
*/
WHOLE
}
/**
* Sends a Text message with characters from the given {@code CharSequence}.
*
* <p> Returns a {@code CompletableFuture<WebSocket>} which completes
* normally when the message has been sent or completes exceptionally if an
* error occurs.
*
* <p> The {@code CharSequence} must not be modified until the returned
* {@code CompletableFuture} completes (either normally or exceptionally).
*
* <p> The returned {@code CompletableFuture} can complete exceptionally
* with:
* <ul>
* <li> {@link IllegalArgumentException} -
* if {@code message} is a malformed UTF-16 sequence
* <li> {@link IllegalStateException} -
* if the {@code WebSocket} is closed;
* or if a Close message has been sent;
* or if there is an outstanding send operation;
* or if a previous Binary message was sent with {@code isLast == false}
* <li> {@link IOException} -
* if an I/O error occurs during this operation;
* or if the {@code WebSocket} has been closed due to an error;
* </ul>
*
* @implNote This implementation does not accept partial UTF-16 sequences.
* In case such a sequence is passed, a returned {@code CompletableFuture}
* completes exceptionally with {@code IOException}.
*
* @param message
* the message
* @param isLast
* {@code true} if this is the last part of the message,
* {@code false} otherwise
*
* @return a {@code CompletableFuture} with this {@code WebSocket}
*/
CompletableFuture<WebSocket> sendText(CharSequence message, boolean isLast);
/**
* Sends a Binary message with bytes from the given {@code ByteBuffer}.
*
* <p> Returns a {@code CompletableFuture<WebSocket>} which completes
* normally when the message has been sent or completes exceptionally if an
* error occurs.
*
* <p> The returned {@code CompletableFuture} can complete exceptionally
* with:
* <ul>
* <li> {@link IllegalStateException} -
* if the {@code WebSocket} is closed;
* or if a Close message has been sent;
* or if there is an outstanding send operation;
* or if a previous Text message was sent with {@code isLast == false}
* <li> {@link IOException} -
* if an I/O error occurs during this operation;
* or if the {@code WebSocket} has been closed due to an error
* </ul>
*
* @param message
* the message
* @param isLast
* {@code true} if this is the last part of the message,
* {@code false} otherwise
*
* @return a {@code CompletableFuture} with this {@code WebSocket}
*/
CompletableFuture<WebSocket> sendBinary(ByteBuffer message, boolean isLast);
/**
* Sends a Ping message with bytes from the given ByteBuffer.
*
* <p> Returns a {@code CompletableFuture<WebSocket>} which completes
* normally when the message has been sent or completes exceptionally if an
* error occurs.
*
* <p> A Ping message may be sent or received by either client or server.
* It may serve either as a keepalive or as a means to verify that the
* remote endpoint is still responsive.
*
* <p> The message must consist of not more than {@code 125} bytes: {@code
* message.remaining() <= 125}.
*
* <p> The returned {@code CompletableFuture} can complete exceptionally
* with:
* <ul>
* <li> {@link IllegalArgumentException} -
* if {@code message.remaining() > 125}
* <li> {@link IllegalStateException} -
* if the {@code WebSocket} is closed;
* or if a Close message has been sent;
* or if there is an outstanding send operation
* <li> {@link IOException} -
* if an I/O error occurs during this operation;
* or if the {@code WebSocket} has been closed due to an error
* </ul>
*
* @param message
* the message
*
* @return a {@code CompletableFuture} with this {@code WebSocket}
*/
CompletableFuture<WebSocket> sendPing(ByteBuffer message);
/**
* Sends a Pong message with bytes from the given ByteBuffer.
*
* <p> Returns a {@code CompletableFuture<WebSocket>} which completes
* normally when the message has been sent or completes exceptionally if an
* error occurs.
*
* <p> A Pong message may be unsolicited or may be sent in response to a
* previously received Ping. In latter case the contents of the Pong must be
* identical to the originating Ping.
*
* <p> The message must consist of not more than {@code 125} bytes: {@code
* message.remaining() <= 125}.
*
* <p> The returned {@code CompletableFuture} can complete exceptionally
* with:
* <ul>
* <li> {@link IllegalArgumentException} -
* if {@code message.remaining() > 125}
* <li> {@link IllegalStateException} -
* if the {@code WebSocket} is closed;
* or if a Close message has been sent;
* or if there is an outstanding send operation
* <li> {@link IOException} -
* if an I/O error occurs during this operation;
* or if the {@code WebSocket} has been closed due to an error
* </ul>
*
* @param message
* the message
*
* @return a {@code CompletableFuture} with this {@code WebSocket}
*/
CompletableFuture<WebSocket> sendPong(ByteBuffer message);
/**
* Sends a Close message with the given status code and the reason.
*
* <p> When this method has been invoked, no further messages can be sent.
*
* <p> The {@code statusCode} is an integer in the range {@code 1000 <= code
* <= 4999}. However, not all status codes may be legal in some
* implementations. Regardless of an implementation,
* <code>{@value jdk.incubator.http.WebSocket#NORMAL_CLOSURE}</code>
* is always legal and {@code 1002}, {@code 1003}, {@code 1005}, {@code
* 1006}, {@code 1007}, {@code 1009}, {@code 1010}, {@code 1012}, {@code
* 1013} and {@code 1015} are always illegal codes.
*
* <p> The {@code reason} is a short string that must have an UTF-8
* representation not longer than {@code 123} bytes. For more details on
* Close message, status codes and reason see RFC 6455 sections
* <a href="https://tools.ietf.org/html/rfc6455#section-5.5.1">5.5.1. Close</a>
* and
* <a href="https://tools.ietf.org/html/rfc6455#section-7.4">7.4. Status Codes</a>.
*
* <p> The method returns a {@code CompletableFuture<WebSocket>} which
* completes normally when the message has been sent or completes
* exceptionally if an error occurs.
*
* <p> The returned {@code CompletableFuture} can complete exceptionally
* with:
* <ul>
* <li> {@link IllegalArgumentException} -
* if the {@code statusCode} has an illegal value;
* or if {@code reason} doesn't have an UTF-8 representation of
* length {@code <= 123}
* <li> {@link IOException} -
* if an I/O error occurs during this operation;
* or the {@code WebSocket} has been closed due to an error
* </ul>
*
* <p> If this method has already been invoked or the {@code WebSocket} is
* closed, then subsequent invocations of this method have no effect and the
* returned {@code CompletableFuture} completes normally.
*
* <p> If a Close message has been {@linkplain Listener#onClose(WebSocket,
* int, String) received} before, then this invocation completes the closing
* handshake and by the time the returned {@code CompletableFuture}
* completes, the {@code WebSocket} will have been closed.
*
* @param statusCode
* the status code
* @param reason
* the reason
*
* @return a {@code CompletableFuture} with this {@code WebSocket}
*/
CompletableFuture<WebSocket> sendClose(int statusCode, String reason);
/**
* Allows {@code n} more messages to be received by the {@link Listener
* Listener}.
*
* <p> The actual number of received messages might be fewer if a Close
* message is received, the {@code WebSocket} closes or an error occurs.
*
* <p> A {@code WebSocket} that has just been built, hasn't requested
* anything yet. Usually the initial request for messages is made in {@link
* Listener#onOpen(jdk.incubator.http.WebSocket) Listener.onOpen}.
*
* <p> If the {@code WebSocket} is closed then invoking this method has no
* effect.
*
* @implNote This implementation does not distinguish between partial and
* whole messages, because it's not known beforehand how a message will be
* received.
*
* <p> If a server sends more messages than requested, this implementation
* queues up these messages on the TCP connection and may eventually force
* the sender to stop sending through TCP flow control.
*
* @param n
* the number of messages
*
* @throws IllegalArgumentException
* if {@code n < 0}
*/
void request(long n);
/**
* Returns a {@linkplain Builder#subprotocols(String, String...) subprotocol}
* which has been chosen for this {@code WebSocket}.
*
* @return a subprotocol, or an empty {@code String} if there is none
*/
String getSubprotocol();
/**
* Tells whether the {@code WebSocket} is closed.
*
* <p> When a {@code WebSocket} is closed no further messages can be sent or
* received.
*
* @return {@code true} if the {@code WebSocket} is closed,
* {@code false} otherwise
*/
boolean isClosed();
/**
* Closes the {@code WebSocket} abruptly.
*
* <p> This method may be invoked at any time. This method closes the
* underlying TCP connection and puts the {@code WebSocket} into a closed
* state.
*
* <p> As the result {@link Listener#onClose(WebSocket, int, String)
* Listener.onClose} will be invoked unless either {@code onClose} or {@link
* Listener#onError(WebSocket, Throwable) onError} has been invoked before.
* In which case no additional invocation will happen.
*
* <p> If the {@code WebSocket} is already closed then invoking this method
* has no effect.
*
* @throws IOException
* if an I/O error occurs
*/
void abort() throws IOException;
}