Orocos/ROS Services tutorial

This tutorial will teach how to set up an Orocos component to expose its Operations as ROS services.


If you don’t have a working version of Orocos + ROS installed in your system, please refer to the first tutorial Installation.

These tutorials assume you have a working knowledge of Orocos components, if not read The Orocos Component Builder’s Manual or follow the basic RTT tutorials.

In this tutorial we will show you how to expose the operations of your Orocos component as ROS services.

In general the signature of the operation you want to expose as a ROS service will have to adhere to the typical ROS service callback:

bool operation(Service::Request&, Service::Response&);


If you want to use custom ROS services, see Defining custom messages.

Take for example the following component:

Header file:


#include <rtt/RTT.hpp>
#include <rtt/Component.hpp>
#include <my_msgs/MyService.h>

class StandardComponent:
    public RTT::TaskContext
    /// Constructor
    StandardComponent(std::string const& name);

    /// Destructor

    bool myOperation(my_msgs::MyService::Request& request, my_msgs::MyService::Response& response)
        response.success = false;
        if (request.data)
            response.success = true;

        return true;

    /// Configure
    bool configureHook();

    /// Update
    void updateHook();

#endif // StandardComponent_H

And cpp file:

#include <orocos-ros-services/StandardComponent.h>

StandardComponent::StandardComponent(std::string const& name)
    : RTT::TaskContext(name)
    this->provides("simple_service")->addOperation("myOperation", &StandardComponent::myOperation, this, RTT::ClientThread);

bool StandardComponent::configureHook()
    return true;

void StandardComponent::updateHook()

    RTT::log(RTT::Info) << "Waking up!" << RTT::endlog();



That exposes an operation using the MyService type from the my_msgs package.

We can deploy with the following script:


loadComponent("my_component", "StandardComponent")

// load the rosservice service in the component
loadService("my_component", "rosservice")

// connect the operation to the ros service:
my_component.rosservice.connect("simple_service.myOperation", "/my_namespace/my_operation", "my_msgs/MyService")

Operations can also be exposed as ROS services without having to adher to the typical bool operation(Service::Request& request, Service::Response& response) interface, with the use of wrappers. For the services in std_srvs the following operation signatures are supported:

- bool empty()                     // The service call fails if empty() returns false!
                                // Use std_srvs/Trigger if the result should be returned as the response.
- void empty()

- bool setBool(bool, std::string &message_out)
- bool setBool(bool)               // response.message will be empty
- std::string setBool(bool)        // response.success = true
- void setBool(bool)               // response.success = true and response.message will be empty

- bool trigger(std::string &message_out)
- bool trigger()                   // response.message will be empty
- std::string trigger()            // response.success = true

This can be extended to other ros service types, see the header files in the rtt_std_srvs package.