jetty-documentation/src/main/asciidoc/development/websockets/jetty/jetty-websocket-api-send-message.adoc - jetty - Git at Google

 //  ========================================================================
 //  Copyright (c) 1995-2017 Mort Bay Consulting Pty. Ltd.
 //  ========================================================================
 //  All rights reserved. This program and the accompanying materials
 //  are made available under the terms of the Eclipse Public License v1.0
 //  and Apache License v2.0 which accompanies this distribution.
 //
 //      The Eclipse Public License is available at
 //      http://www.eclipse.org/legal/epl-v10.html
 //
 //      The Apache License v2.0 is available at
 //      http://www.opensource.org/licenses/apache2.0.php
 //
 //  You may elect to redistribute this code under either of these licenses.
 //  ========================================================================

 [[jetty-websocket-api-send-message]]
 === Send Messages to Remote Endpoint

 The most important feature of the Session is access to the link:{JDURL}/org/eclipse/jetty/websocket/api/RemoteEndpoint.html[`org.eclipse.jetty.websocket.api.RemoteEndpoint`]needed to send messages.

 With RemoteEndpoint you can choose to send TEXT or BINARY WebSocket messages, or the WebSocket PING and PONG control frames.

 [[blocking]]
 ==== Blocking Send Message

 Most calls are blocking in nature, and will not return until the send has completed (or has thrown an exception).

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Blocking Send of a BINARY message to remote endpoint
 ByteBuffer buf = ByteBuffer.wrap(new byte[] { 0x11, 0x22, 0x33, 0x44 });
 try
 {
     remote.sendBytes(buf);
 }
 catch (IOException e)
 {
     e.printStackTrace(System.err);
 }
 ----

 How to send a simple Binary message using the RemoteEndpoint.
 This will block until the message is sent, possibly throwing an IOException if unable to send the message.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Blocking Send of a TEXT message to remote endpoint
 try
 {
     remote.sendString("Hello World");
 }
 catch (IOException e)
 {
     e.printStackTrace(System.err);
 }
 ----

 How to send a simple Text message using the RemoteEndpoint.
 This will block until the message is sent, possibly throwing an IOException if unable to send the message.

 [[partial]]
 ==== Send Partial Message

 If you have a large message to send, and want to send it in pieces and parts, you can utilize the partial message sending methods of RemoteEndpoint.
 Just be sure you finish sending your message (`isLast == true`).

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Blocking Send of a BINARY message to remote endpoint
 // Part 1
 ByteBuffer buf1 = ByteBuffer.wrap(new byte[] { 0x11, 0x22 });
 // Part 2 (last part)
 ByteBuffer buf2 = ByteBuffer.wrap(new byte[] { 0x33, 0x44 });
 try
 {
     remote.sendPartialBytes(buf1,false);
     remote.sendPartialBytes(buf2,true); // isLast is true
 }
 catch (IOException e)
 {
     e.printStackTrace(System.err);
 }
 ----

 How to send a Binary message in 2 parts, using the partial message support in RemoteEndpoint.
 This will block until each part of the message is sent, possibly throwing an IOException if unable to send the partial message.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Blocking Send of a TEXT message to remote endpoint
 String part1 = "Hello";
 String part2 = " World";
 try
 {
     remote.sendPartialString(part1,false);
     remote.sendPartialString(part2,true); // last part
 }
 catch (IOException e)
 {
     e.printStackTrace(System.err);
 }
 ----

 How to send a Text message in 2 parts, using the partial message support in RemoteEndpoint.
 This will block until each part of the message is sent, possibly throwing an IOException if unable to send the partial message.

 [[pingpong]]
 ==== Send Ping / Pong Control Frame

 You can also send Ping and Pong control frames using the RemoteEndpoint.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Blocking Send of a PING to remote endpoint
 String data = "You There?";
 ByteBuffer payload = ByteBuffer.wrap(data.getBytes());
 try
 {
     remote.sendPing(payload);
 }
 catch (IOException e)
 {
     e.printStackTrace(System.err);
 }
 ----

 How to send a Ping control frame, with a payload of `"You There?"` (arriving at Remote Endpoint as a byte array payload).
 This will block until the message is sent, possibly throwing an IOException if unable to send the ping frame.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Blocking Send of a PONG to remote endpoint
 String data = "Yup, I'm here";
 ByteBuffer payload = ByteBuffer.wrap(data.getBytes());
 try
 {
     remote.sendPong(payload);
 }
 catch (IOException e)
 {
     e.printStackTrace(System.err);
 }
 ----

 How to send a Pong control frame, with a payload of `"Yup I'm here"` (arriving at Remote Endpoint as a byte array payload).
 This will block until the message is sent, possibly throwing an IOException if unable to send the pong frame.

 To be correct in your usage of Pong frames, you should return the same byte array data that you received in the Ping frame.

 [[async]]
 ==== Async Send Message

 However there are also 2 Async send message methods available:

 * link:{JDURL}/org/eclipse/jetty/websocket/api/RemoteEndpoint.html#sendBytesByFuture(java.nio.ByteBuffer)[`RemoteEndpoint.sendBytesByFuture(ByteBuffer message)`]
 * link:{JDURL}/org/eclipse/jetty/websocket/api/RemoteEndpoint.html#sendStringByFuture(java.lang.String)[`RemoteEndpoint.sendStringByFuture(String message)`]

 Both return a `Future<Void>` that can be used to test for success and failure of the message send using standard http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/Future.html[`java.util.concurrent.Future`] behavior.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Async Send of a BINARY message to remote endpoint
 ByteBuffer buf = ByteBuffer.wrap(new byte[] { 0x11, 0x22, 0x33, 0x44 });
 remote.sendBytesByFuture(buf);
 ----

 How to send a simple Binary message using the RemoteEndpoint.
 The message will be enqueued for outgoing write, but you will not know if it succeeded or failed.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Async Send of a BINARY message to remote endpoint
 ByteBuffer buf = ByteBuffer.wrap(new byte[] { 0x11, 0x22, 0x33, 0x44 });
 try
 {
     Future<Void> fut = remote.sendBytesByFuture(buf);
     // wait for completion (forever)
     fut.get();
 }
 catch (ExecutionException | InterruptedException e)
 {
     // Send failed
     e.printStackTrace();
 }
 ----

 How to send a simple Binary message using the RemoteEndpoint, tracking the `Future<Void>` to know if the send succeeded or failed.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Async Send of a BINARY message to remote endpoint
 ByteBuffer buf = ByteBuffer.wrap(new byte[] { 0x11, 0x22, 0x33, 0x44 });
 Future<Void> fut = null;
 try
 {
     fut = remote.sendBytesByFuture(buf);
     // wait for completion (timeout)
     fut.get(2,TimeUnit.SECONDS);
 }
 catch (ExecutionException | InterruptedException e)
 {
     // Send failed
     e.printStackTrace();
 }
 catch (TimeoutException e)
 {
     // timeout
     e.printStackTrace();
     if (fut != null)
     {
         // cancel the message
         fut.cancel(true);
     }
 }
 ----

 How to send a simple Binary message using the RemoteEndpoint, tracking the `Future<Void>` and waiting only prescribed amount of time for the send to complete, cancelling the message if the timeout occurs.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Async Send of a TEXT message to remote endpoint
 remote.sendStringByFuture("Hello World");
 ----

 How to send a simple Text message using the RemoteEndpoint.
 The message will be enqueued for outgoing write, but you will not know if it succeeded or failed.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Async Send of a TEXT message to remote endpoint
 try
 {
     Future<Void> fut = remote.sendStringByFuture("Hello World");
     // wait for completion (forever)
     fut.get();
 }
 catch (ExecutionException | InterruptedException e)
 {
     // Send failed
     e.printStackTrace();
 }
 ----

 How to send a simple Binary message using the RemoteEndpoint, tracking the `Future<Void>` to know if the send succeeded or failed.

 [source, java, subs="{sub-order}"]
 ----
 RemoteEndpoint remote = session.getRemote();

 // Async Send of a TEXT message to remote endpoint
 Future<Void> fut = null;
 try
 {
     fut = remote.sendStringByFuture("Hello World");
     // wait for completion (timeout)
     fut.get(2,TimeUnit.SECONDS);
 }
 catch (ExecutionException | InterruptedException e)
 {
     // Send failed
     e.printStackTrace();
 }
 catch (TimeoutException e)
 {
     // timeout
     e.printStackTrace();
     if (fut != null)
     {
         // cancel the message
         fut.cancel(true);
     }
 }
 ----

 How to send a simple Binary message using the RemoteEndpoint, tracking the `Future<Void>` and waiting only prescribed amount of time for the send to complete, cancelling the message if the timeout occurs.
	// ========================================================================
	// Copyright (c) 1995-2017 Mort Bay Consulting Pty. Ltd.
	// ========================================================================
	// All rights reserved. This program and the accompanying materials
	// are made available under the terms of the Eclipse Public License v1.0
	// and Apache License v2.0 which accompanies this distribution.
	//
	// The Eclipse Public License is available at
	// http://www.eclipse.org/legal/epl-v10.html
	//
	// The Apache License v2.0 is available at
	// http://www.opensource.org/licenses/apache2.0.php
	//
	// You may elect to redistribute this code under either of these licenses.
	// ========================================================================

	[[jetty-websocket-api-send-message]]
	=== Send Messages to Remote Endpoint

	The most important feature of the Session is access to the link:{JDURL}/org/eclipse/jetty/websocket/api/RemoteEndpoint.html[`org.eclipse.jetty.websocket.api.RemoteEndpoint`]needed to send messages.

	With RemoteEndpoint you can choose to send TEXT or BINARY WebSocket messages, or the WebSocket PING and PONG control frames.

	[[blocking]]
	==== Blocking Send Message

	Most calls are blocking in nature, and will not return until the send has completed (or has thrown an exception).

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Blocking Send of a BINARY message to remote endpoint
	ByteBuffer buf = ByteBuffer.wrap(new byte[] { 0x11, 0x22, 0x33, 0x44 });
	try
	{
	remote.sendBytes(buf);
	}
	catch (IOException e)
	{
	e.printStackTrace(System.err);
	}
	----

	How to send a simple Binary message using the RemoteEndpoint.
	This will block until the message is sent, possibly throwing an IOException if unable to send the message.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Blocking Send of a TEXT message to remote endpoint
	try
	{
	remote.sendString("Hello World");
	}
	catch (IOException e)
	{
	e.printStackTrace(System.err);
	}
	----

	How to send a simple Text message using the RemoteEndpoint.
	This will block until the message is sent, possibly throwing an IOException if unable to send the message.

	[[partial]]
	==== Send Partial Message

	If you have a large message to send, and want to send it in pieces and parts, you can utilize the partial message sending methods of RemoteEndpoint.
	Just be sure you finish sending your message (`isLast == true`).

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Blocking Send of a BINARY message to remote endpoint
	// Part 1
	ByteBuffer buf1 = ByteBuffer.wrap(new byte[] { 0x11, 0x22 });
	// Part 2 (last part)
	ByteBuffer buf2 = ByteBuffer.wrap(new byte[] { 0x33, 0x44 });
	try
	{
	remote.sendPartialBytes(buf1,false);
	remote.sendPartialBytes(buf2,true); // isLast is true
	}
	catch (IOException e)
	{
	e.printStackTrace(System.err);
	}
	----

	How to send a Binary message in 2 parts, using the partial message support in RemoteEndpoint.
	This will block until each part of the message is sent, possibly throwing an IOException if unable to send the partial message.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Blocking Send of a TEXT message to remote endpoint
	String part1 = "Hello";
	String part2 = " World";
	try
	{
	remote.sendPartialString(part1,false);
	remote.sendPartialString(part2,true); // last part
	}
	catch (IOException e)
	{
	e.printStackTrace(System.err);
	}
	----

	How to send a Text message in 2 parts, using the partial message support in RemoteEndpoint.
	This will block until each part of the message is sent, possibly throwing an IOException if unable to send the partial message.

	[[pingpong]]
	==== Send Ping / Pong Control Frame

	You can also send Ping and Pong control frames using the RemoteEndpoint.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Blocking Send of a PING to remote endpoint
	String data = "You There?";
	ByteBuffer payload = ByteBuffer.wrap(data.getBytes());
	try
	{
	remote.sendPing(payload);
	}
	catch (IOException e)
	{
	e.printStackTrace(System.err);
	}
	----

	How to send a Ping control frame, with a payload of `"You There?"` (arriving at Remote Endpoint as a byte array payload).
	This will block until the message is sent, possibly throwing an IOException if unable to send the ping frame.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Blocking Send of a PONG to remote endpoint
	String data = "Yup, I'm here";
	ByteBuffer payload = ByteBuffer.wrap(data.getBytes());
	try
	{
	remote.sendPong(payload);
	}
	catch (IOException e)
	{
	e.printStackTrace(System.err);
	}
	----

	How to send a Pong control frame, with a payload of `"Yup I'm here"` (arriving at Remote Endpoint as a byte array payload).
	This will block until the message is sent, possibly throwing an IOException if unable to send the pong frame.

	To be correct in your usage of Pong frames, you should return the same byte array data that you received in the Ping frame.

	[[async]]
	==== Async Send Message

	However there are also 2 Async send message methods available:

	* link:{JDURL}/org/eclipse/jetty/websocket/api/RemoteEndpoint.html#sendBytesByFuture(java.nio.ByteBuffer)[`RemoteEndpoint.sendBytesByFuture(ByteBuffer message)`]
	* link:{JDURL}/org/eclipse/jetty/websocket/api/RemoteEndpoint.html#sendStringByFuture(java.lang.String)[`RemoteEndpoint.sendStringByFuture(String message)`]

	Both return a `Future<Void>` that can be used to test for success and failure of the message send using standard http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/Future.html[`java.util.concurrent.Future`] behavior.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Async Send of a BINARY message to remote endpoint
	ByteBuffer buf = ByteBuffer.wrap(new byte[] { 0x11, 0x22, 0x33, 0x44 });
	remote.sendBytesByFuture(buf);
	----

	How to send a simple Binary message using the RemoteEndpoint.
	The message will be enqueued for outgoing write, but you will not know if it succeeded or failed.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Async Send of a BINARY message to remote endpoint
	ByteBuffer buf = ByteBuffer.wrap(new byte[] { 0x11, 0x22, 0x33, 0x44 });
	try
	{
	Future<Void> fut = remote.sendBytesByFuture(buf);
	// wait for completion (forever)
	fut.get();
	}
	catch (ExecutionException \| InterruptedException e)
	{
	// Send failed
	e.printStackTrace();
	}
	----

	How to send a simple Binary message using the RemoteEndpoint, tracking the `Future<Void>` to know if the send succeeded or failed.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Async Send of a BINARY message to remote endpoint
	ByteBuffer buf = ByteBuffer.wrap(new byte[] { 0x11, 0x22, 0x33, 0x44 });
	Future<Void> fut = null;
	try
	{
	fut = remote.sendBytesByFuture(buf);
	// wait for completion (timeout)
	fut.get(2,TimeUnit.SECONDS);
	}
	catch (ExecutionException \| InterruptedException e)
	{
	// Send failed
	e.printStackTrace();
	}
	catch (TimeoutException e)
	{
	// timeout
	e.printStackTrace();
	if (fut != null)
	{
	// cancel the message
	fut.cancel(true);
	}
	}
	----

	How to send a simple Binary message using the RemoteEndpoint, tracking the `Future<Void>` and waiting only prescribed amount of time for the send to complete, cancelling the message if the timeout occurs.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Async Send of a TEXT message to remote endpoint
	remote.sendStringByFuture("Hello World");
	----

	How to send a simple Text message using the RemoteEndpoint.
	The message will be enqueued for outgoing write, but you will not know if it succeeded or failed.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Async Send of a TEXT message to remote endpoint
	try
	{
	Future<Void> fut = remote.sendStringByFuture("Hello World");
	// wait for completion (forever)
	fut.get();
	}
	catch (ExecutionException \| InterruptedException e)
	{
	// Send failed
	e.printStackTrace();
	}
	----

	How to send a simple Binary message using the RemoteEndpoint, tracking the `Future<Void>` to know if the send succeeded or failed.

	[source, java, subs="{sub-order}"]
	----
	RemoteEndpoint remote = session.getRemote();

	// Async Send of a TEXT message to remote endpoint
	Future<Void> fut = null;
	try
	{
	fut = remote.sendStringByFuture("Hello World");
	// wait for completion (timeout)
	fut.get(2,TimeUnit.SECONDS);
	}
	catch (ExecutionException \| InterruptedException e)
	{
	// Send failed
	e.printStackTrace();
	}
	catch (TimeoutException e)
	{
	// timeout
	e.printStackTrace();
	if (fut != null)
	{
	// cancel the message
	fut.cancel(true);
	}
	}
	----

	How to send a simple Binary message using the RemoteEndpoint, tracking the `Future<Void>` and waiting only prescribed amount of time for the send to complete, cancelling the message if the timeout occurs.