ros2actionclient
Description
Use the ros2actionclient
object to connect to an action server
and request the execution of action goals. You can send multiple goals from an action client,
get feedback on the execution progress, and cancel goals at any time.
Creation
Syntax
Description
creates a client for the ROS 2 action with name client
= ros2actionclient(node
,actionname
,actiontype
)actionname
and type
actiontype
. It attaches the action client to the ROS 2 node
specified by the ros2node
object,
node
. If the action server offering
actionname
is not available, the function does not display an
error.
sets the rest of the properties based on the additional options specified by one or more
client
= ros2actionclient(node
,actionname
,actiontype
,Name=Value)Name=Value
pair arguments.
[
returns a goal message initialized with default values for the action type of the
client, using any of the arguments from the previous syntaxes. You can use this message
to modify the goal and send it to the action server.client
,goalMsg
] = ros2actionclient(___)
Properties
ActionName
— ROS 2 action name
string scalar | character vector
ROS 2 action name, returned as a character vector. The action name must match one of
the topics that ros2 action list
outputs. For more information, see
ros2
.
ActionType
— Action type for ROS 2 action
string scalar | character vector
Action type for a ROS action, returned as a string scalar or character vector. You
can get the action type of an action using ros2 action type
<action_name>
. For more information, see ros2
.
IsServerConnected
— Indicates if client is connected to ROS 2 action server
false
(default) | true
This property is read-only.
Indicator of whether the client is connected to a ROS 2 action server, returned as
false
or true
. Use
waitForserver
to wait until the server is connected when setting
up an action client.
GoalServiceQoS
— Quality of Service (QoS) settings for sending goal
'History: keeplast, Depth: 10, Reliability: reliable,
Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease
Duration: Inf'
(default) | structure
Quality of Service (QoS) settings for sending goal to the action server, returned as a character vector. When you set this QoS setting as a name-value argument, you must specify it as a structure with the one or more of these fields:
History
Depth
Reliability
Durability
Deadline
Lifespan
Lease Duration
Liveliness
ResultServiceQoS
— Quality of Service (QoS) settings for getting result
'History: keeplast, Depth: 10, Reliability: reliable,
Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease
Duration: Inf'
(default) | structure
Quality of Service (QoS) settings for getting result from the action server, returned as a character vector. When you set this QoS setting as a name-value argument, you must specify it as a structure with the one or more of these fields:
History
Depth
Reliability
Durability
Deadline
Lifespan
Lease Duration
Liveliness
CancelServiceQoS
— Quality of Service (QoS) settings for canceling goal
'History: keeplast, Depth: 10, Reliability: reliable,
Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease
Duration: Inf'
(default) | structure
Quality of Service (QoS) settings for canceling goals sent to the action server, returned as a character vector. When you set this QoS setting as a name-value argument, you must specify it as a structure with the one or more of these fields:
History
Depth
Reliability
Durability
Deadline
Lifespan
Lease Duration
Liveliness
FeedbackTopicQoS
— Quality of Service (QoS) settings for receiving feedback
'History: keeplast, Depth: 10, Reliability: reliable,
Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease
Duration: Inf'
(default) | structure
Quality of Service (QoS) settings for receiving feedback from the action server, returned as a character vector. When you set this QoS setting as a name-value argument, you must specify it as a structure with the one or more of these fields:
History
Depth
Reliability
Durability
Deadline
Lifespan
Lease Duration
Liveliness
StatusTopicQoS
— Quality of Service (QoS) settings for receiving goal status
'History: keeplast, Depth: 10, Reliability: reliable,
Durability: volatile, Deadline: Inf, Lifespan: Inf, Liveliness: automatic, Lease
Duration: Inf'
(default) | structure
Quality of Service (QoS) settings for receiving goal execution status from the action server, returned as a character vector. When you set this QoS setting as a name-value argument, you must specify it as a structure with the one or more of these fields:
History
Depth
Reliability
Durability
Deadline
Lifespan
Liveliness
Lease Duration
Object Functions
ros2message | Create ROS 2 message structures |
waitForServer | Wait for ROS 2 action server to be ready for sending goals |
sendGoal | Send goal message to ROS 2 action server |
getStatus | Get execution status of specific goal sent by ROS 2 action client |
getResult | Get result of specific goal associated with goal handle |
cancelGoal | Cancel specific goal sent by ROS 2 action client |
cancelGoalAndWait | Cancel specific goal sent by ROS 2 action client and wait for cancel response |
cancelGoalsBefore | Cancel goals sent by ROS 2 action client before timestamp |
cancelGoalsBeforeAndWait | Cancel goals sent by ROS 2 action client before timestamp and wait for cancel response |
cancelAllGoals | Cancel all active goals sent by ROS 2 action client |
cancelAllGoalsAndWait | Cancel all active goals sent by ROS 2 action client and wait for cancel response |
Examples
Set Up ROS 2 Action Client and Execute an Action
This example shows how to create a ROS 2 action client and execute the action. Action types must be set up beforehand with an action server running. This example uses the /fibonacci
action. Follow these steps to set up the action server:
Create a ROS 2 package with the action definition. For instructions on setting up a /
fibonacci
action, see Creating an Action.Create a ROS 2 package with the action server implementation. For more information on setting up the
/fibonacci
action server, see Writing an Action Server.Use the
ros2genmsg
function for the ROS 2 package with action definition from Step 1, and generate action messages in MATLAB®.
To run the /fibonacci
action server, use this command on the ROS 2 system:
ros2 run action_tutorials_cpp fibonacci_action_server
Set Up ROS 2 Action Client
List the actions available on the network. The /fibonacci
action must be on the list.
ros2 action list
/fibonacci
Get the action type for the /fibonacci
action.
ros2 action type /fibonacci
action_tutorials_interfaces/Fibonacci
Create a ROS 2 node.
node = ros2node("/node_1");
Create an action client by specifying the node, action name, and action type. Set the quality of service (QoS) parameters.
[client,goalMsg] = ros2actionclient(node,"fibonacci",... "action_tutorials_interfaces/Fibonacci", ... CancelServiceQoS=struct(Depth=200,History="keeplast"), ... FeedbackTopicQoS=struct(Depth=200,History="keepall"));
Wait for the action client to connect to the server.
status = waitForServer(client)
status = logical
1
The /fibonacci
action will calculate the Fibonacci sequence for a given order specified in the goal message. The goal message was returned when creating the action client and can be modified to send goals to the ROS action server. Set the order to an int32
value of 8. If the input requires a 1-D array, set it as a column vector.
goalMsg.order = int32(8);
Send Goal and Execute Action
Before sending the goal, define the callback options framework for the goal execution process. In this example, you specify a callback function to execute when the server returns a feedback response and the final result using the name-value arguments.
callbackOpts = ros2ActionSendGoalOptions(FeedbackFcn=@helperFeedbackCallback,ResultFcn=@helperResultCallback);
Send the goal to the action server using the sendGoal
function. Specify the callback options. During goal execution, you see outputs from the feedback and result callbacks displayed on the MATLAB® command window.
goalHandle = sendGoal(client,goalMsg,callbackOpts);
Goal with GoalUUID 3d10ab880f960666fde5666f45f621a accepted by server, waiting for result! Partial sequence feedback for goal 3d10ab880f960666fde5666f45f621a is 0 1 1 Partial sequence feedback for goal 3d10ab880f960666fde5666f45f621a is 0 1 1 2 Partial sequence feedback for goal 3d10ab880f960666fde5666f45f621a is 0 1 1 2 3 Partial sequence feedback for goal 3d10ab880f960666fde5666f45f621a is 0 1 1 2 3 5 Partial sequence feedback for goal 3d10ab880f960666fde5666f45f621a is 0 1 1 2 3 5 8 Partial sequence feedback for goal 3d10ab880f960666fde5666f45f621a is 0 1 1 2 3 5 8 13 Partial sequence feedback for goal 3d10ab880f960666fde5666f45f621a is 0 1 1 2 3 5 8 13 21 Full sequence result for goal 3d10ab880f960666fde5666f45f621a is 0 1 1 2 3 5 8 13 21
Get the status of goal execution.
exStatus = getStatus(client,goalHandle)
exStatus = int8
2
Get the result using the action client and goal handle inputs. Display the result. The getResult
function returns the sequence as a column vector.
resultMsg = getResult(client,goalHandle); rosShowDetails(resultMsg)
ans = ' MessageType : action_tutorials_interfaces/FibonacciResult sequence : [0, 1, 1, 2, 3, 5, 8, 13, 21]'
Alternatively, you can only use the goal handle as input to get the result.
resultMsg = getResult(goalHandle); rosShowDetails(resultMsg)
ans = ' MessageType : action_tutorials_interfaces/FibonacciResult sequence : [0, 1, 1, 2, 3, 5, 8, 13, 21]'
Helper Functions
helperFeedbackCallback
defines the callback function to execute when the client receives a feedback response from the action server.
function helperFeedbackCallback(goalHandle,feedbackMsg) seq = feedbackMsg.partial_sequence; disp(['Partial sequence feedback for goal ',goalHandle.GoalUUID,' is ',num2str(seq')]) end
helperResultCallback
defines the callback function to execute when the client receives the result message from the action server.
function helperResultCallback(goalHandle,wrappedResultMsg) seq = wrappedResultMsg.result.sequence; disp(['Full sequence result for goal ',goalHandle.GoalUUID,' is ',num2str(seq')]) end
Send and Cancel ROS 2 Action Goals
This example shows how to send and cancel ROS 2 action goals. Action types must be set up beforehand with an action server running. This example uses the /fibonacci
action. Follow these steps to set up the action server:
Create a ROS 2 package with the action definition. For instructions on setting up a /
fibonacci
action, see Creating an Action.Create a ROS 2 package with the action server implementation. For more information on setting up the
/fibonacci
action server, see Writing an Action Server.Use the
ros2genmsg
function for the ROS 2 package with action definition from Step 1, and generate action messages in MATLAB®.
To run the /fibonacci
action server, use this command on the ROS 2 system:
ros2 run action_tutorials_cpp fibonacci_action_server
Set Up ROS 2 Action Client
Create a ROS 2 node.
node = ros2node("/node_1");
Create an action client for /fibonacci
action by specifying the node, action name, and action type. Set the quality of service (QoS) parameters.Wait for the action client to connect to the server.
[client,goalMsg] = ros2actionclient(node,"fibonacci",... "action_tutorials_interfaces/Fibonacci", ... CancelServiceQoS=struct(Depth=200,History="keeplast"), ... FeedbackTopicQoS=struct(Depth=200,History="keepall")); status = waitForServer(client)
status = logical
1
Before sending the goal, define the callback options framework for the goal execution process. In this example, you specify a callback function to execute when the server returns a feedback response.
callbackOpts = ros2ActionSendGoalOptions(FeedbackFcn=@helperFeedbackCallback);
Send and Cancel Goals
The /fibonacci
action will calculate the /fibonacci
sequence for a given order specified in the goal message. The goal message was returned when creating the action client and can be modified to send goals to the ROS action server. Set the order to an int32
value of 8.
goalMsg.order = int32(8);
Create a new goal message and set the order to an int32
value of 10.
goalMsg2 = ros2message(client); goalMsg2.order = int32(10);
Send both the goals to the action server using the sendGoal
function. Specify the same callback options for both goals.
goalHandle = sendGoal(client,goalMsg,callbackOpts); goalHandle2 = sendGoal(client,goalMsg2,callbackOpts);
Goal with GoalUUID ca8dbca2b8608a6f2add01b298f6930 accepted by server, waiting for result! Partial sequence feedback for goal ca8dbca2b8608a6f2add01b298f6930 is 0 1 1 Goal with GoalUUID f493913f4acd2224f31145ae74bbc35 accepted by server, waiting for result! Partial sequence feedback for goal f493913f4acd2224f31145ae74bbc35 is 0 1 1
Cancel the specific goal associated with the sequence order 8
. Use the goal handle object associated with that goal as input to the cancelGoal
function, and specify the cancel callback to execute once the client receives the cancel response. This function returns immediately without waiting for the cancel response to arrive.
cancelGoal(client,goalHandle,CancelFcn=@helperCancelGoalCallback)
Goal ca8dbca2b8608a6f2add01b298f6930 is cancelled with return code 0
You can wait until the cancel response arrives from the server by using the cancelGoalAndWait
function. Cancel the goal associated with the sequence order of 10 and wait until the client receives the cancel response.
cancelResponse = cancelGoalAndWait(client,goalHandle2)
cancelResponse = struct with fields:
MessageType: 'action_msgs/CancelGoalResponse'
ERROR_NONE: 0
ERROR_REJECTED: 1
ERROR_UNKNOWN_GOAL_ID: 2
ERROR_GOAL_TERMINATED: 3
return_code: 0
goals_canceling: [1×1 struct]
Cancel Goals Before Timestamp
Send the goal message with sequence order 10
. Note the timestamp in a ROS 2 message by using the ros2time
function.
goalHandle = sendGoal(client,goalMsg2,callbackOpts);
timeStampMsg = ros2time(node,"now");
Goal with GoalUUID d8268c566b234e8784f0f1a8ec12b2 accepted by server, waiting for result! Partial sequence feedback for goal d8268c566b234e8784f0f1a8ec12b2 is 0 1 1
Then, send a second goal message with sequence order 8
. Note the timestamp.
goalHandle2 = sendGoal(client,goalMsg,callbackOpts);
timeStampMsg2 = ros2time(node,"now");
Goal with GoalUUID 9585bff2ba44bf60daa630a952b458be accepted by server, waiting for result! Partial sequence feedback for goal 9585bff2ba44bf60daa630a952b458be is 0 1 1
Cancel the goal sent before the first time stamp using cancelGoalsBefore
function.
cancelGoalsBefore(client,timeStampMsg,CancelFcn=@helperCancelGoalsCallback)
Goals cancelled with return code 0
Use the cancelGoalsBeforeAndWait
function to cancel the goal sent before second time stamp and wait for the cancel response.
cancelResponse = cancelGoalsBeforeAndWait(client,timeStampMsg2)
cancelResponse = struct with fields:
MessageType: 'action_msgs/CancelGoalResponse'
ERROR_NONE: 0
ERROR_REJECTED: 1
ERROR_UNKNOWN_GOAL_ID: 2
ERROR_GOAL_TERMINATED: 3
return_code: 0
goals_canceling: [1×1 struct]
Cancel All Goals
Cancel all the active goals that the client sent.
goalHandle = sendGoal(client,goalMsg,callbackOpts); cancelAllGoals(client,CancelFcn=@helperCancelGoalsCallback);
Goals cancelled with return code 0
Cancel all the active goals that the client sent and wait for cancel response.
goalHandle2 = sendGoal(client,goalMsg2,callbackOpts); cancelResponse = cancelAllGoalsAndWait(client)
cancelResponse = struct with fields:
MessageType: 'action_msgs/CancelGoalResponse'
ERROR_NONE: 0
ERROR_REJECTED: 1
ERROR_UNKNOWN_GOAL_ID: 2
ERROR_GOAL_TERMINATED: 3
return_code: 0
goals_canceling: [1×1 struct]
Helper Functions
helperFeedbackCallback
defines the callback function to execute when the client receives a feedback response from the action server.
function helperFeedbackCallback(goalHandle,feedbackMsg) seq = feedbackMsg.partial_sequence; disp(['Partial sequence feedback for goal ',goalHandle.GoalUUID,' is ',num2str(seq')]) end
helperCancelGoalCallback
defines the callback function to execute when the client receives a cancel response after canceling a specific goal.
function helperCancelGoalCallback(goalHandle,cancelMsg) code = cancelMsg.return_code; disp(['Goal ',goalHandle.GoalUUID,' is cancelled with return code ',num2str(code)]) end
helperCancelGoalsCallback
defines the callback function to execute when the client receives a cancel response after canceling a set of goals.
function helperCancelGoalsCallback(cancelMsg) code = cancelMsg.return_code; disp(['Goals cancelled with return code ',num2str(code)]) end
Limitations
If a ROS 2 action server and the action clients connected to it are running in the same MATLAB® session, the server cannot process cancel requests from the client.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
The callback functions used to send and cancel goals must be specified when you create the
ros2actionclient
object using these name-value arguments.'SendGoalOptions'
— Specify a cell array of callback options structures for sending goals that you create using theros2ActionSendGoalOptions
function.'CancelFcn'
— Specify the cancel response callback that you use with thecancelGoal
function.'CancelAllFcn'
— Specify the cancel response callback that you use with thecancelAllGoals
function.'CancelBeforeFcn'
— Specify the cancel response callback that you use with thecancelGoalsBefore
function.
Note that these arguments are used for definition of
ros2actionclient
only and must be specified again at the time of usage in the respective function.callbackOpts1 = ros2ActionSendGoalOptions(FeedbackFcn=@glfeedback,ResultFcn=@glResult); callbackOpts2 = ros2ActionSendGoalOptions(FeedbackFcn=@glfeedback2,ResultFcn=@glResult2); [client] = ros2actionClient(node,"my_action","my_action_type",SendGoalOptions={callbackOpts1,callbackOpts2},CancelFcn=@cancelGoalCB,CancelAllFcn=@cancelGoalsCB); goalMsg = ros2message(client); goalHandle = sendGoal(client,goalMsg,callbackOpts1); cancelGoal(client,goalHandle,CancelFcn=@cancelGoalCB);
The syntax with
goalMsg
output argument is not supported.[client,goalMsg] = ros2actionClient(node,"my_action","my_action_type")
When you create callback options to send goals using the
ros2ActionSendGoalOptions
function, any additional input arguments toGoalRespFcn
,FeedbackFcn
and,ResultFcn
callbacks are not supported. Only the function signatures with the goal handle and received message as input arguments is supported.
Version History
Introduced in R2023a
See Also
ros2actionserver
| sendGoal
| getResult
| getStatus
| cancelGoal
| waitForServer
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