/*
* Copyright (c) 2015, 2018, 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
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package java.net.http;
import java.io.IOException;
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.
*
* <p> {@code WebSocket} instances are created through {@link WebSocket.Builder}.
*
* <p> WebSocket has an input and an output sides. These sides are independent
* from each other. A side can either be open or closed. Once closed, the side
* remains closed. WebSocket messages are sent through a {@code WebSocket} and
* received through a {@code WebSocket.Listener} associated with it. Messages
* can be sent until the WebSocket's output is closed, and received until the
* WebSocket's input is closed.
*
* <p> A send method is any of the {@code sendText}, {@code sendBinary},
* {@code sendPing}, {@code sendPong} and {@code sendClose} methods of
* {@code WebSocket}. A send method initiates a send operation and returns a
* {@code CompletableFuture} which completes once the operation has completed.
* If the {@code CompletableFuture} completes normally the operation is
* considered succeeded. If the {@code CompletableFuture} completes
* exceptionally, the operation is considered failed. An operation that has been
* initiated but not yet completed is considered pending.
*
* <p> A receive method is any of the {@code onText}, {@code onBinary},
* {@code onPing}, {@code onPong} and {@code onClose} methods of
* {@code Listener}. WebSocket initiates a receive operation by invoking a
* receive method on the listener. The listener then must return a
* {@code CompletionStage} which completes once the operation has completed.
*
* <p> To control receiving of messages, a WebSocket maintains an
* <a id="counter">internal counter</a>. This counter's value is a number of
* times the WebSocket has yet to invoke a receive method. While this counter is
* zero the WebSocket does not invoke receive methods. The counter is
* incremented by {@code n} when {@code request(n)} is called. The counter is
* decremented by one when the WebSocket invokes a receive method.
* {@code onOpen} and {@code onError} are not receive methods. WebSocket invokes
* {@code onOpen} prior to any other methods on the listener. WebSocket invokes
* {@code onOpen} at most once. WebSocket may invoke {@code onError} at any
* given time. If the WebSocket invokes {@code onError} or {@code onClose}, then
* no further listener's methods will be invoked, no matter the value of the
* counter. For a newly built WebSocket the counter is zero.
*
* <p> Unless otherwise stated, {@code null} arguments will cause methods
* of {@code WebSocket} to throw {@code NullPointerException}, similarly,
* {@code WebSocket} will not pass {@code null} arguments to methods of
* {@code Listener}. The state of a WebSocket is not changed by the invocations
* that throw or return a {@code CompletableFuture} that completes with one of
* the {@code NullPointerException}, {@code IllegalArgumentException},
* {@code IllegalStateException} exceptions.
*
* <p> {@code WebSocket} handles received Ping and Close messages automatically
* (as per the WebSocket Protocol) by replying with Pong and Close messages. If
* the listener receives Ping or Close messages, no mandatory actions from the
* listener are required.
*
* @apiNote The relationship between a WebSocket and the associated Listener is
* analogous to that of a Subscription and the associated Subscriber of type
* {@link java.util.concurrent.Flow}.
*
* @since 11
*/
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 of {@linkplain WebSocket WebSocket Clients}.
*
* <p> Builders are created by invoking
* {@link HttpClient#newWebSocketBuilder HttpClient.newWebSocketBuilder}.
* The intermediate (setter-like) methods change the state of the builder
* and return the same builder they have been invoked on. If an intermediate
* method is not invoked, an appropriate default value (or behavior) will be
* assumed. A {@code Builder} is not safe for use by multiple threads
* without external synchronization.
*
* @since 11
*/
interface Builder {
/**
* Adds the given name-value pair to the list of additional HTTP headers
* sent during the opening handshake.
*
* <p> Headers defined in the
* <a href="https://tools.ietf.org/html/rfc6455#section-11.3">WebSocket
* Protocol</a> are illegal. If this method is not invoked, no
* additional HTTP headers will be sent.
*
* @param name
* the header name
* @param value
* the header value
*
* @return this builder
*/
Builder header(String name, String value);
/**
* Sets a timeout for establishing a WebSocket connection.
*
* <p> If the connection is not established within the specified
* duration then building of the {@code WebSocket} will fail with
* {@link HttpTimeoutException}. If this method is not invoked then the
* infinite timeout is assumed.
*
* @param timeout
* the timeout, non-{@linkplain Duration#isNegative() negative},
* non-{@linkplain Duration#ZERO ZERO}
*
* @return this builder
*/
Builder connectTimeout(Duration timeout);
/**
* Sets a request for the given subprotocols.
*
* <p> After the {@code WebSocket} has been built, the actual
* subprotocol can be queried through
* {@link WebSocket#getSubprotocol WebSocket.getSubprotocol()}.
*
* <p> Subprotocols are specified in the order of preference. The most
* preferred subprotocol is specified first. If there are any additional
* subprotocols they are enumerated from the most preferred to the least
* preferred.
*
* <p> Subprotocols not conforming to the syntax of subprotocol
* identifiers are illegal. If this method is not invoked then no
* subprotocols will be requested.
*
* @param mostPreferred
* the most preferred subprotocol
* @param lesserPreferred
* the lesser preferred subprotocols
*
* @return this builder
*/
Builder subprotocols(String mostPreferred, String... lesserPreferred);
/**
* Builds a {@link WebSocket} connected to the given {@code URI} and
* associated with the given {@code Listener}.
*
* <p> Returns a {@code CompletableFuture} which will either complete
* normally with the resulting {@code WebSocket} or complete
* exceptionally with one of 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 timeout
* <li> {@link InterruptedException} -
* if the operation is interrupted
* <li> {@link SecurityException} -
* if a security manager has been installed and it denies
* {@link java.net.URLPermission access} to {@code uri}.
* <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 arguments of this builder's methods are
* illegal
* </ul>
*
* @param uri
* the WebSocket URI
* @param listener
* the listener
*
* @return a {@code CompletableFuture} with the {@code WebSocket}
*/
CompletableFuture<WebSocket> buildAsync(URI uri, Listener listener);
}
/**
* The receiving interface of {@code WebSocket}.
*
* <p> A {@code WebSocket} invokes methods of the associated listener
* passing itself as an argument. These methods are invoked in a thread-safe
* manner, such that the next invocation may start only after the previous
* one has finished.
*
* <p> When data has been received, the {@code WebSocket} invokes a receive
* method. Methods {@code onText}, {@code onBinary}, {@code onPing} and
* {@code onPong} must return a {@code CompletionStage} that completes once
* the message has been received by the listener. If a listener's method
* returns {@code null} rather than a {@code CompletionStage},
* {@code WebSocket} will behave as if the listener returned a
* {@code CompletionStage} that is already completed normally.
*
* <p> An {@code IOException} raised in {@code WebSocket} will result in an
* invocation of {@code onError} with that exception (if the input is not
* closed). Unless otherwise stated if the listener's method throws an
* exception or a {@code CompletionStage} returned from a method completes
* exceptionally, the WebSocket will invoke {@code onError} with this
* exception.
*
* @apiNote <p> The strict sequential order of invocations from
* {@code WebSocket} to {@code Listener} means, in particular, that
* {@code Listener}'s methods are treated as non-reentrant. Which means that
* {@code Listener} implementations do not need to be concerned with
* possible recursion or the order in which they call
* {@code WebSocket.request} in relation to their processing logic.
*
* <p> Careful attention may be required if a listener is associated
* with more than a single {@code WebSocket}. In this case invocations
* related to different instances of {@code WebSocket} may not be ordered
* and may even happen concurrently.
*
* <p> {@code CompletionStage}s returned from the receive methods have
* nothing to do with the
* <a href="WebSocket.html#counter">counter of invocations</a>.
* Namely, a {@code CompletionStage} does not have to be completed in order
* to receive more invocations of the listener's methods.
* Here is an example of a listener that requests invocations, one at a
* time, until a complete message has been accumulated, then processes
* the result, and completes the {@code CompletionStage}:
* <pre>{@code WebSocket.Listener listener = new WebSocket.Listener() {
*
* List<CharSequence> parts = new ArrayList<>();
* CompletableFuture<?> accumulatedMessage = new CompletableFuture<>();
*
* public CompletionStage<?> onText(WebSocket webSocket,
* CharSequence message,
* boolean last) {
* parts.add(message);
* webSocket.request(1);
* if (last) {
* processWholeText(parts);
* parts = new ArrayList<>();
* accumulatedMessage.complete(null);
* CompletionStage<?> cf = accumulatedMessage;
* accumulatedMessage = new CompletableFuture<>();
* return cf;
* }
* return accumulatedMessage;
* }
* ...
* } } </pre>
*
* @since 11
*/
interface Listener {
/**
* A {@code WebSocket} has been connected.
*
* <p> This is the initial invocation and it is made once. It is
* typically used to make a request for more invocations.
*
* @implSpec The default implementation is equivalent to:
* <pre>{@code webSocket.request(1); }</pre>
*
* @param webSocket
* the WebSocket that has been connected
*/
default void onOpen(WebSocket webSocket) { webSocket.request(1); }
/**
* A textual data has been received.
*
* <p> Return a {@code CompletionStage} which will be used by the
* {@code WebSocket} as an indication it may reclaim the
* {@code CharSequence}. Do not access the {@code CharSequence} after
* this {@code CompletionStage} has completed.
*
* @implSpec The default implementation is equivalent to:
* <pre>{@code webSocket.request(1);
* return null; }</pre>
*
* @implNote The {@code data} is always a legal UTF-16 sequence.
*
* @param webSocket
* the WebSocket on which the data has been received
* @param data
* the data
* @param last
* whether this invocation completes the message
*
* @return a {@code CompletionStage} which completes when the
* {@code CharSequence} may be reclaimed; or {@code null} if it may be
* reclaimed immediately
*/
default CompletionStage<?> onText(WebSocket webSocket,
CharSequence data,
boolean last) {
webSocket.request(1);
return null;
}
/**
* A binary data has been received.
*
* <p> This data is located in bytes from the buffer's position to its
* limit.
*
* <p> Return a {@code CompletionStage} which will be used by the
* {@code WebSocket} as an indication it may reclaim the
* {@code ByteBuffer}. Do not access the {@code ByteBuffer} after
* this {@code CompletionStage} has completed.
*
* @implSpec The default implementation is equivalent to:
* <pre>{@code webSocket.request(1);
* return null; }</pre>
*
* @param webSocket
* the WebSocket on which the data has been received
* @param data
* the data
* @param last
* whether this invocation completes the message
*
* @return a {@code CompletionStage} which completes when the
* {@code ByteBuffer} may be reclaimed; or {@code null} if it may be
* reclaimed immediately
*/
default CompletionStage<?> onBinary(WebSocket webSocket,
ByteBuffer data,
boolean last) {
webSocket.request(1);
return null;
}
/**
* A Ping message has been received.
*
* <p> As guaranteed by the WebSocket Protocol, the message consists of
* not more than {@code 125} bytes. These bytes are located from the
* buffer's position to its limit.
*
* <p> Given that the WebSocket implementation will automatically send a
* reciprocal pong when a ping is received, it is rarely required to
* send a pong message explicitly when a ping is received.
*
* <p> Return a {@code CompletionStage} which will be used by the
* {@code WebSocket} as a signal it may reclaim the
* {@code ByteBuffer}. Do not access the {@code ByteBuffer} after
* this {@code CompletionStage} has completed.
*
* @implSpec The default implementation is equivalent to:
* <pre>{@code webSocket.request(1);
* return null; }</pre>
*
* @param webSocket
* the WebSocket on which the message has been received
* @param message
* the message
*
* @return a {@code CompletionStage} which completes when the
* {@code ByteBuffer} may be reclaimed; or {@code null} if it may be
* reclaimed immediately
*/
default CompletionStage<?> onPing(WebSocket webSocket,
ByteBuffer message) {
webSocket.request(1);
return null;
}
/**
* A Pong message has been received.
*
* <p> As guaranteed by the WebSocket Protocol, the message consists of
* not more than {@code 125} bytes. These bytes are located from the
* buffer's position to its limit.
*
* <p> Return a {@code CompletionStage} which will be used by the
* {@code WebSocket} as a signal it may reclaim the
* {@code ByteBuffer}. Do not access the {@code ByteBuffer} after
* this {@code CompletionStage} has completed.
*
* @implSpec The default implementation is equivalent to:
* <pre>{@code webSocket.request(1);
* return null; }</pre>
*
* @param webSocket
* the WebSocket on which the message has been received
* @param message
* the message
*
* @return a {@code CompletionStage} which completes when the
* {@code ByteBuffer} may be reclaimed; or {@code null} if it may be
* reclaimed immediately
*/
default CompletionStage<?> onPong(WebSocket webSocket,
ByteBuffer message) {
webSocket.request(1);
return null;
}
/**
* Receives a Close message indicating the WebSocket's input has been
* closed.
*
* <p> This is the last invocation from the specified {@code WebSocket}.
* By the time this invocation begins the WebSocket's input will have
* been closed.
*
* <p> A Close message consists of a status code and a reason for
* closing. The status code is an integer from the range
* {@code 1000 <= code <= 65535}. The {@code reason} is a string which
* has a UTF-8 representation not longer than {@code 123} bytes.
*
* <p> If the WebSocket's output is not already closed, the
* {@code CompletionStage} returned by this method will be used as an
* indication that the WebSocket's output may be closed. The WebSocket
* will close its output at the earliest of completion of the returned
* {@code CompletionStage} or invoking either of the {@code sendClose}
* or {@code abort} methods.
*
* @apiNote Returning a {@code CompletionStage} that never completes,
* effectively disables the reciprocating closure of the output.
*
* <p> To specify a custom closure code or reason code the
* {@code sendClose} method may be invoked from inside the
* {@code onClose} invocation:
* <pre>{@code public CompletionStage<?> onClose(WebSocket webSocket,
* int statusCode,
* String reason) {
* webSocket.sendClose(CUSTOM_STATUS_CODE, CUSTOM_REASON);
* return new CompletableFuture<Void>();
* } } </pre>
*
* @implSpec The default implementation of this method returns
* {@code null}, indicating that the output should be closed
* immediately.
*
* @param webSocket
* the WebSocket on which the message has been received
* @param statusCode
* the status code
* @param reason
* the reason
*
* @return a {@code CompletionStage} which completes when the
* {@code WebSocket} may be closed; or {@code null} if it may be
* closed immediately
*/
default CompletionStage<?> onClose(WebSocket webSocket,
int statusCode,
String reason) {
return null;
}
/**
* An error has occurred.
*
* <p> This is the last invocation from the specified WebSocket. By the
* time this invocation begins both the WebSocket's input and output
* will have been closed. A WebSocket may invoke this method on the
* associated listener at any time after it has invoked {@code onOpen},
* regardless of whether or not any invocations have been requested from
* the WebSocket.
*
* <p> If an exception is thrown from this method, resulting behavior is
* undefined.
*
* @param webSocket
* the WebSocket on which the error has occurred
* @param error
* the error
*/
default void onError(WebSocket webSocket, Throwable error) { }
}
/**
* Sends textual data with characters from the given character sequence.
*
* <p> The character sequence must not be modified until the
* {@code CompletableFuture} returned from this method has completed.
*
* <p> A {@code CompletableFuture} returned from this method can
* complete exceptionally with:
* <ul>
* <li> {@link IllegalStateException} -
* if there is a pending text or binary send operation
* or if the previous binary data does not complete the message
* <li> {@link IOException} -
* if an I/O error occurs, or if the output is closed
* </ul>
*
* @implNote If {@code data} is a malformed UTF-16 sequence, the operation
* will fail with {@code IOException}.
*
* @param data
* the data
* @param last
* {@code true} if this invocation completes the message,
* {@code false} otherwise
*
* @return a {@code CompletableFuture} that completes, with this WebSocket,
* when the data has been sent
*/
CompletableFuture<WebSocket> sendText(CharSequence data, boolean last);
/**
* Sends binary data with bytes from the given buffer.
*
* <p> The data is located in bytes from the buffer's position to its limit.
* Upon normal completion of a {@code CompletableFuture} returned from this
* method the buffer will have no remaining bytes. The buffer must not be
* accessed until after that.
*
* <p> The {@code CompletableFuture} returned from this method can
* complete exceptionally with:
* <ul>
* <li> {@link IllegalStateException} -
* if there is a pending text or binary send operation
* or if the previous textual data does not complete the message
* <li> {@link IOException} -
* if an I/O error occurs, or if the output is closed
* </ul>
*
* @param data
* the data
* @param last
* {@code true} if this invocation completes the message,
* {@code false} otherwise
*
* @return a {@code CompletableFuture} that completes, with this WebSocket,
* when the data has been sent
*/
CompletableFuture<WebSocket> sendBinary(ByteBuffer data, boolean last);
/**
* Sends a Ping message with bytes from the given buffer.
*
* <p> The message consists of not more than {@code 125} bytes from the
* buffer's position to its limit. Upon normal completion of a
* {@code CompletableFuture} returned from this method the buffer will
* have no remaining bytes. The buffer must not be accessed until after that.
*
* <p> The {@code CompletableFuture} returned from this method can
* complete exceptionally with:
* <ul>
* <li> {@link IllegalStateException} -
* if there is a pending ping or pong send operation
* <li> {@link IllegalArgumentException} -
* if the message is too long
* <li> {@link IOException} -
* if an I/O error occurs, or if the output is closed
* </ul>
*
* @param message
* the message
*
* @return a {@code CompletableFuture} that completes, with this WebSocket,
* when the Ping message has been sent
*/
CompletableFuture<WebSocket> sendPing(ByteBuffer message);
/**
* Sends a Pong message with bytes from the given buffer.
*
* <p> The message consists of not more than {@code 125} bytes from the
* buffer's position to its limit. Upon normal completion of a
* {@code CompletableFuture} returned from this method the buffer will have
* no remaining bytes. The buffer must not be accessed until after that.
*
* <p> Given that the WebSocket implementation will automatically send a
* reciprocal pong when a ping is received, it is rarely required to send a
* pong message explicitly.
*
* <p> The {@code CompletableFuture} returned from this method can
* complete exceptionally with:
* <ul>
* <li> {@link IllegalStateException} -
* if there is a pending ping or pong send operation
* <li> {@link IllegalArgumentException} -
* if the message is too long
* <li> {@link IOException} -
* if an I/O error occurs, or if the output is closed
* </ul>
*
* @param message
* the message
*
* @return a {@code CompletableFuture} that completes, with this WebSocket,
* when the Pong message has been sent
*/
CompletableFuture<WebSocket> sendPong(ByteBuffer message);
/**
* Initiates an orderly closure of this WebSocket's output by
* sending a Close message with the given status code and the reason.
*
* <p> The {@code statusCode} is an integer from the range
* {@code 1000 <= code <= 4999}. Status codes {@code 1002}, {@code 1003},
* {@code 1006}, {@code 1007}, {@code 1009}, {@code 1010}, {@code 1012},
* {@code 1013} and {@code 1015} are illegal. Behaviour in respect to other
* status codes is implementation-specific. A legal {@code reason} is a
* string that has a UTF-8 representation not longer than {@code 123} bytes.
*
* <p> A {@code CompletableFuture} returned from this method can
* complete exceptionally with:
* <ul>
* <li> {@link IllegalArgumentException} -
* if {@code statusCode} is illegal, or
* if {@code reason} is illegal
* <li> {@link IOException} -
* if an I/O error occurs, or if the output is closed
* </ul>
*
* <p> Unless the {@code CompletableFuture} returned from this method
* completes with {@code IllegalArgumentException}, or the method throws
* {@code NullPointerException}, the output will be closed.
*
* <p> If not already closed, the input remains open until a Close message
* {@linkplain Listener#onClose(WebSocket, int, String) received}, or
* {@code abort} is invoked, or an
* {@linkplain Listener#onError(WebSocket, Throwable) error} occurs.
*
* @apiNote Use the provided integer constant {@link #NORMAL_CLOSURE} as a
* status code and an empty string as a reason in a typical case:
* <pre>{@code CompletableFuture<WebSocket> webSocket = ...
* webSocket.thenCompose(ws -> ws.sendText("Hello, ", false))
* .thenCompose(ws -> ws.sendText("world!", true))
* .thenCompose(ws -> ws.sendClose(WebSocket.NORMAL_CLOSURE, ""))
* .join(); }</pre>
*
* The {@code sendClose} method does not close this WebSocket's input. It
* merely closes this WebSocket's output by sending a Close message. To
* enforce closing the input, invoke the {@code abort} method. Here is an
* example of an application that sends a Close message, and then starts a
* timer. Once no data has been received within the specified timeout, the
* timer goes off and the alarm aborts {@code WebSocket}:
* <pre>{@code MyAlarm alarm = new MyAlarm(webSocket::abort);
* WebSocket.Listener listener = new WebSocket.Listener() {
*
* public CompletionStage<?> onText(WebSocket webSocket,
* CharSequence data,
* boolean last) {
* alarm.snooze();
* ...
* }
* ...
* };
* ...
* Runnable startTimer = () -> {
* MyTimer idleTimer = new MyTimer();
* idleTimer.add(alarm, 30, TimeUnit.SECONDS);
* };
* webSocket.sendClose(WebSocket.NORMAL_CLOSURE, "ok").thenRun(startTimer);
* } </pre>
*
* @param statusCode
* the status code
* @param reason
* the reason
*
* @return a {@code CompletableFuture} that completes, with this WebSocket,
* when the Close message has been sent
*/
CompletableFuture<WebSocket> sendClose(int statusCode, String reason);
/**
* Increments the counter of invocations of receive methods.
*
* <p> This WebSocket will invoke {@code onText}, {@code onBinary},
* {@code onPing}, {@code onPong} or {@code onClose} methods on the
* associated listener (i.e. receive methods) up to {@code n} more times.
*
* @apiNote The parameter of this method is the number of invocations being
* requested from this WebSocket to the associated listener, not the number
* of messages. Sometimes a message may be delivered to the listener in a
* single invocation, but not always. For example, Ping, Pong and Close
* messages are delivered in a single invocation of {@code onPing},
* {@code onPong} and {@code onClose} methods respectively. However, whether
* or not Text and Binary messages are delivered in a single invocation of
* {@code onText} and {@code onBinary} methods depends on the boolean
* argument ({@code last}) of these methods. If {@code last} is
* {@code false}, then there is more to a message than has been delivered to
* the invocation.
*
* <p> Here is an example of a listener that requests invocations, one at a
* time, until a complete message has been accumulated, and then processes
* the result:
* <pre>{@code WebSocket.Listener listener = new WebSocket.Listener() {
*
* StringBuilder text = new StringBuilder();
*
* public CompletionStage<?> onText(WebSocket webSocket,
* CharSequence message,
* boolean last) {
* text.append(message);
* if (last) {
* processCompleteTextMessage(text);
* text = new StringBuilder();
* }
* webSocket.request(1);
* return null;
* }
* ...
* } } </pre>
*
* @param n
* the number of invocations
*
* @throws IllegalArgumentException
* if {@code n <= 0}
*/
void request(long n);
/**
* Returns the subprotocol used by this WebSocket.
*
* @return the subprotocol, or an empty string if there's no subprotocol
*/
String getSubprotocol();
/**
* Tells whether this WebSocket's output is closed.
*
* <p> If this method returns {@code true}, subsequent invocations will also
* return {@code true}.
*
* @return {@code true} if closed, {@code false} otherwise
*/
boolean isOutputClosed();
/**
* Tells whether this WebSocket's input is closed.
*
* <p> If this method returns {@code true}, subsequent invocations will also
* return {@code true}.
*
* @return {@code true} if closed, {@code false} otherwise
*/
boolean isInputClosed();
/**
* Closes this WebSocket's input and output abruptly.
*
* <p> When this method returns both the input and the output will have been
* closed. Any pending send operations will fail with {@code IOException}.
* Subsequent invocations of {@code abort} will have no effect.
*/
void abort();
}