ROS subscriber callback is not triggered when the master is run from ros hydro

I have the following setup in Linux: 1- ros core (hydro) running on a separate terminal. 2- stage publish LIDAR message and others... 3- Matlab subscribing to Lidar messages and displaying a message every time a message is received.

Verified: 1- rostopic list shows the Lidar data is publish at an average 10 Hz rate 2- Matlab node is recognized by ros as a subscriber to the Lidar topic (/base_scan)

Problem: The call back function never gets triggered.

Note: I tried a similar setup with roscore running on Matlab with publisher & subscriber to Lidar data, and that worked...

code:

node = rosmatlab.node('LidarPlotter', 'http://localhost:11311');
subscriber = rosmatlab.subscriber('/base_scan', 'sensor_msgs/LaserScan', 10, node);
subscriber.setOnNewMessageListeners({@LidarPlot});
pause(10);
node.removeSubscriber(subscriber);
% Delete the master.
clear('roscore');
%%Clean up workspace.
clear;

Function code:

function LidarPlot(x)
disp('a lidar message has been received');

[Felix Burget]

Hi Utayba,

i am having the same problem. Just trying so use Matlab to plot some data in real time while running a ROS application. I already tried to receive messages in matlab using

rostopic pub /TOPIC std_msgs/String 'Hello'

without success. The communication between ROS & Matlab does not seem to be bidirectional. There's also no example or tutorial explaining how messages published from ROS are received by a Matlab subscriber. Hope to get some info soon.

Best, Felix

[Soner Ulun]

Hi,

Were you able to run any of the examples? When I try rosmatlab_basic I receive the following error:

>> rosmatlab_basic
Undefined variable "org" or class "org.ros.RosCore.newPublic".

Error in rosmatlab.roscore (line 62)
                rosMaster = org.ros.RosCore.newPublic(port);

Error in rosmatlab_basic (line 4)
roscore = rosmatlab.roscore(11311);

Do i need to install any other packages for Hydro? I just download and installed the source from matlab. There is no tutorial or proper instructions for this package, so any help is apriciated.

Bests,

Soner

[Daniel]

I have the same problem in hydro. I have try with many official and unofficial messages, but communication is only works from Matlab to ROS. However when nodes are create with Matlab communication is bidirectional.

Soner Ulun: Are you in the correct path?

Answer 1

[Jaime]

Hi, i found a solution and post it in http://answers.ros.org/questions/

here it is the link : http://answers.ros.org/question/130356/how-to-subscribe-to-topics-using-ros-support-from-matlab/?answer=132381#post-id-132381

I hope it will work for you as well.

Greets, Jaime

[Utayba Mohammad]

Thanks Jaime,

That worked for me. Following up on your solution I notice that when you don't specify ROS_MASTER_URI, roscore uses a default value of "http://ubuntu:11311" so Matlab was communicating with ROS properly using localhost or explicit IP but not the other way around.