ros

Class RosBridge

java.lang.Object

ros.RosBridge

@WebSocket
public class RosBridge
extends Object

A socket for connecting to ros bridge that accepts subscribe and publish commands. Subscribing to a topic using the subscribe(SubscriptionRequestMsg, RosListenDelegate). The input SubscriptionRequestMsg allows you to iteratively build all the optional fields you can set to detail the subscription, such as whether the messages should be fragmented in size, the queue length, throttle rate, etc. If data is pushed quickly, it is recommended that you set the throttle rate and queue length to 1 or you may observe increasing latency in the messages. Png compression is currently not supported. If the message type is not set, and the topic either does not exist or you have never subscribed to that topic previously, Rosbridge may fail to subscribe. There are also additional methods for subscribing that take the parameters of a subscription as arguments to the method.

Publishing is also supported with the publish(String, String, Object) method, but you should consider using the Publisher class wrapper for streamlining publishing.

To create and connect to rosbridge, you can either instantiate with the default constructor and then call connect(String) or use the static method createConnection(String) which creates a RosBridge instance and then connects. An example URI to provide as a parameter is: ws://localhost:9090, where 9090 is the default Rosbridge server port.

If you need to handle messages with larger sizes, you should subclass RosBridge and annotate the class with WebSocket with the parameter maxTextMessageSize set to the desired buffer size. For example:

@WebSocket(maxTextMessageSize = 500 * 1024) 
public class BigRosBridge extends RosBridge{

}

Note that the subclass does not need to override any methods; subclassing is performed purely to set the buffer size in the annotation value. Then you can instantiate BigRosBridge and call its inherited connect method.

Author:

James MacGlashan.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	RosBridge.FragmentManager
static class	RosBridge.RosBridgeSubscriber Class for managing all the listeners that have subscribed to a topic on Rosbridge.

Field Summary

Fields

Modifier and Type	Field and Description
protected CountDownLatch	closeLatch
protected Map<String,RosBridge.FragmentManager>	fragementManagers
protected boolean	hasConnected
protected Map<String,RosBridge.RosBridgeSubscriber>	listeners
protected boolean	printMessagesAsReceived
protected Set<String>	publishedTopics
protected org.eclipse.jetty.websocket.api.Session	session

Constructor Summary

Constructors

Constructor and Description
RosBridge()

Method Summary

Modifier and Type	Method and Description
void	advertise(String topic, String type) Advertises that this object will be publishing to a ROS topic.
boolean	awaitClose(int duration, TimeUnit unit) Use this to close the connection
void	connect(String rosBridgeURI) Connects to the Rosbridge host at the provided URI.
void	connect(String rosBridgeURI, boolean waitForConnection) Connects to the Rosbridge host at the provided URI.
static RosBridge	createConnection(String rosBridgeURI) Creates a default RosBridge and connects it to the ROS Bridge websocket server located at rosBridgeURI.
void	formatAndSend(Object o) Attempts to turn the the provided object into a JSON message and send it to the ROSBridge server.
boolean	hasConnected() Indicates whether the connection has been made
void	onClose(int statusCode, String reason)
void	onConnect(org.eclipse.jetty.websocket.api.Session session)
void	onMessage(String msg)
boolean	printMessagesAsReceived() Returns whether ROSBridge will print all ROSBridge messages as they are received to the command line.
protected void	processFragment(com.fasterxml.jackson.databind.JsonNode node)
void	publish(String topic, String type, Object msg) Publishes to a topic.
void	publishJsonMsg(String topic, String type, String jsonMsg) Publishes to a topic with a ros message represented in its JSON string form.
void	removeListener(String topic, RosListenDelegate delegate) Stops a RosListenDelegate from receiving messages from Rosbridge.
void	sendRawMessage(String message) Sends the provided fully specified message to the ROS Bridge server.
void	setPrintMessagesAsReceived(boolean printMessagesAsReceived) Sets whether ROSBridge should print all ROSBridge messages as they are received to the command.
void	subscribe(String topic, String type, RosListenDelegate delegate) Subscribes to a ros topic.
void	subscribe(String topic, String type, RosListenDelegate delegate, int throttleRate, int queueLength) Subscribes to a ros topic.
void	subscribe(SubscriptionRequestMsg request, RosListenDelegate delegate) Subscribes to a topic with the subscription parameters specified in the provided SubscriptionRequestMsg.
void	unsubscribe(String topic) Unsubscribes from a topic.
void	waitForConnection() Blocks execution until a connection to the ros bridge server is established.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

closeLatch

protected final CountDownLatch closeLatch

session

protected org.eclipse.jetty.websocket.api.Session session

listeners

protected Map<String,RosBridge.RosBridgeSubscriber> listeners

publishedTopics

protected Set<String> publishedTopics

fragementManagers

protected Map<String,RosBridge.FragmentManager> fragementManagers

hasConnected

protected boolean hasConnected

printMessagesAsReceived

protected boolean printMessagesAsReceived

Constructor Detail

RosBridge

public RosBridge()

Method Detail

createConnection

public static RosBridge createConnection(String rosBridgeURI)

Creates a default RosBridge and connects it to the ROS Bridge websocket server located at rosBridgeURI. Note that it is recommend that you call the waitForConnection() method before publishing or subscribing.

Parameters:

rosBridgeURI - the URI to the ROS Bridge websocket server. Note that ROS Bridge by default uses port 9090. An example URI is: ws://localhost:9090

Returns:

the ROS Bridge socket that is connected to the indicated server.

connect

public void connect(String rosBridgeURI)

Connects to the Rosbridge host at the provided URI.

Parameters:

rosBridgeURI - the URI to the ROS Bridge websocket server. Note that ROS Bridge by default uses port 9090. An example URI is: ws://localhost:9090

connect

public void connect(String rosBridgeURI,
                    boolean waitForConnection)

Connects to the Rosbridge host at the provided URI.

Parameters:

rosBridgeURI - the URI to the ROS Bridge websocket server. Note that ROS Bridge by default uses port 9090. An example URI is: ws://localhost:9090

waitForConnection - if true, then this method will block until the connection is established. If false, then return immediately.

waitForConnection

public void waitForConnection()

Blocks execution until a connection to the ros bridge server is established.

hasConnected

public boolean hasConnected()

Indicates whether the connection has been made

Returns:

a boolean indicating whether the connection has been made

printMessagesAsReceived

public boolean printMessagesAsReceived()

Returns whether ROSBridge will print all ROSBridge messages as they are received to the command line.

Returns:

if true, then ROSBridge will print all ROSBridge messages as they are received to the command line. Otherwise is silent.

setPrintMessagesAsReceived

public void setPrintMessagesAsReceived(boolean printMessagesAsReceived)

Sets whether ROSBridge should print all ROSBridge messages as they are received to the command.

Parameters:

printMessagesAsReceived - if true, then ROSBridge will print all ROSBridge messages as they are received to the command line. Otherwise is silent.

awaitClose

public boolean awaitClose(int duration,
                          TimeUnit unit)
                   throws InterruptedException

Use this to close the connection

Parameters:

duration - the time in some units until closing.

unit - the unit of time in which duration is measured.

Returns:

the result of the CountDownLatch.await() method.

Throws:

InterruptedException

onClose

@OnWebSocketClose
public void onClose(int statusCode,
                                      String reason)

onConnect

@OnWebSocketConnect
public void onConnect(org.eclipse.jetty.websocket.api.Session session)

onMessage

@OnWebSocketMessage
public void onMessage(String msg)

subscribe

public void subscribe(String topic,
                      String type,
                      RosListenDelegate delegate)

Subscribes to a ros topic. New publish results will be reported to the provided delegate. If message type is null, then the type will be inferred. When type is null, if a topic does not already exist, subscribe will fail.

Parameters:

topic - the to subscribe to

type - the message type of the topic. Pass null for type inference.

delegate - the delegate that receives updates to the topic

subscribe

public void subscribe(String topic,
                      String type,
                      RosListenDelegate delegate,
                      int throttleRate,
                      int queueLength)

Subscribes to a ros topic. New publish results will be reported to the provided delegate. If message type is null, then the type will be inferred. When type is null, if a topic does not already exist, subscribe will fail.

Parameters:

topic - the to subscribe to

type - the message type of the topic. Pass null for type inference.

delegate - the delegate that receives updates to the topic

throttleRate - the minimum amount of time (in ms) that must elapse between messages being sent from the server

queueLength - the size of the queue to buffer messages. Messages are buffered as a result of the throttle_rate.

subscribe

public void subscribe(SubscriptionRequestMsg request,
                      RosListenDelegate delegate)

Subscribes to a topic with the subscription parameters specified in the provided SubscriptionRequestMsg. The RosListenDelegate will be notified every time there is a publish to the specified topic.

Parameters:

request - the subscription request details.

delegate - the delegate that will receive messages each time a message is published to the topic.

removeListener

public void removeListener(String topic,
                           RosListenDelegate delegate)

Stops a RosListenDelegate from receiving messages from Rosbridge.

Parameters:

topic - the topic on which the listener subscribed.

delegate - the delegate to remove.

advertise

public void advertise(String topic,
                      String type)

Advertises that this object will be publishing to a ROS topic.

Parameters:

topic - the topic to which this object will be publishing.

type - the ROS message type of the topic.

unsubscribe

public void unsubscribe(String topic)

Unsubscribes from a topic. Note that if there are multiple RosListenDelegate objects subscribed to a topic, they will all unsubscribe. If you want to remove only one, instead use removeListener(String, RosListenDelegate).

Parameters:

topic - the topic from which to unsubscribe.

publish

public void publish(String topic,
                    String type,
                    Object msg)

Publishes to a topic. If the topic has not already been advertised on ros, it will automatically do so.

Parameters:

topic - the topic to publish to

type - the message type of the topic

msg - should be a Map or a Java Bean, specifying the ROS message

publishJsonMsg

public void publishJsonMsg(String topic,
                           String type,
                           String jsonMsg)

Publishes to a topic with a ros message represented in its JSON string form. If the topic has not already been advertised on ros, it will automatically do so.

Parameters:

topic - the topic to publish to

type - the message type of the topic

jsonMsg - the JSON string of the ROS message.

sendRawMessage

public void sendRawMessage(String message)

Sends the provided fully specified message to the ROS Bridge server. Since the RosBridge server expects JSON messages, the string message should probably be in JSON format and adhere to the R Rosbridge protocol, but this method will send whatever raw string you provide.

Parameters:

message - the message to send to Rosbridge.

formatAndSend

public void formatAndSend(Object o)

Attempts to turn the the provided object into a JSON message and send it to the ROSBridge server. If the object does not satisfy the Rosbridge protocol, it may have no affect.

Parameters:

o - the object to turn into a JSON message and send.

processFragment

protected void processFragment(com.fasterxml.jackson.databind.JsonNode node)