send

Publish ROS message to topic

Syntax

send(pub,msg)

Description

send(pub,msg) publishes a message to the topic specified by the publisher, pub. This message can be received by all subscribers in the ROS network that are subscribed to the topic specified by pub.

Examples

Create, Send, and Receive ROS Messages

Set up a publisher and subscriber to send and receive a message on a ROS network.

Connect to a ROS network.

rosinit

Launching ROS Core...
Done in 0.60613 seconds.
Initializing ROS master on http://172.20.24.202:50740.
Initializing global node /matlab_global_node_67937 with NodeURI http://dcc2856820glnxa64:34863/ and MasterURI http://localhost:50740.

Create a publisher with a specific topic and message type. You can also return a default message to send using this publisher.

[pub,msg] = rospublisher('position','geometry_msgs/Point');

Modify the message before sending it over the network.

msg.X = 1;
msg.Y = 2;
send(pub,msg);

Create a subscriber and wait for the latest message. Verify the message is the one you sent.

sub = rossubscriber('position')

sub = 
  Subscriber with properties:

                      TopicName: '/position'
                  LatestMessage: [1×1 Point]
                    MessageType: 'geometry_msgs/Point'
                     BufferSize: 1
    MessagePreprocessingEnabled: 0
                  NewMessageFcn: []
                     DataFormat: 'object'

pause(1);
sub.LatestMessage

ans = 
  ROS Point message with properties:

    MessageType: 'geometry_msgs/Point'
              X: 1
              Y: 2
              Z: 0

  Use showdetails to show the contents of the message

Shut down the ROS network.

rosshutdown

Shutting down global node /matlab_global_node_67937 with NodeURI http://dcc2856820glnxa64:34863/ and MasterURI http://localhost:50740.
Shutting down ROS master on http://172.20.24.202:50740.

Input Arguments

pub — ROS publisher

Publisher object handle

ROS publisher, specified as a Publisher object handle. You can create the object using rospublisher.

msg — ROS message

Message object handle | structure

ROS message, specified as a Message object handle or structure. You can create object using rosmessage.

Note

In a future release, ROS Toolbox will use message structures instead of objects for ROS messages.

To use message structures now, set the "DataFormat" name-value argument to "struct". For more information, see ROS Message Structures.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Supported only for struct messages.

Version History

Introduced in R2019b

R2021a: ROS Message Structures

You can now create messages as structures with fields matching the message object properties. Using structures typically improves performance of creating, updating, and using ROS messages, but message fields are no longer validated when set. Message types and corresponding field values from the structures are validated when sent across the network.

To use ROS messages as structures, use the "DataFormat" name-value argument when creating your publishers, subscribers, or other ROS objects. Any messages generated from these objects will utilize structures.

pub = rospublisher("/scan","sensor_msgs/LaserScan","DataFormat","struct")
msg = rosmessage(pub)

You can also create messages as structures directly, but make sure to specify the data format as "struct" for the publisher, subscriber, or other ROS objects as well. ROS objects still use message objects by default.

msg = rosmessage("/scan","sensor_msgs/LaserScan","DataFormat","struct")
...
pub = rospublisher("/scan","sensor_msgs/LaserScan","DataFormat","struct")

In a future release, ROS messages will use structures by default and ROS message objects will be removed.

For more information, see Improve Performance of ROS Using Message Structures.