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Fast DDS System Handle

Introduction

What is a System Handle?

A System Handle is a plugin that allows a certain middleware or communication protocol to speak the same language used by the eProsima Integration Service, that is, Extensible and Dynamic Topic Types for DDS (xTypes); specifically, Integration Service bases its intercommunication abilities on eProsima's open source implementation for the xTypes protocol, that is, eProsima xTypes.

The Fast DDS SystemHandle

This repository contains the source code of the Integration Service System Handle for eProsima's open source implementation of the DDS protocol, that is, Fast DDS.

This System Handle can be used for three main purposes:

Connection between a DDS application and an application running over a different middleware implementation. This is the classic use-case approach for Integration Service.
Connecting two DDS applications running under different Domain IDs.
Creating a TCP tunnel, by running an Integration Service instance on each of the machines you want to establish a communication between.

Dependencies

This section provides a list of the dependencies needed in order to compile FastDDS System Handle.

FastDDS: eProsima C++ implementation for DDS.

Configuration

Integration Service is configured by means of a YAML configuration file, which specifies the middlewares, topics and/or services involved in the intercommunication process, as well as their topic/service types and the data exchange flow. This configuration file is loaded at runtime, so there is no need to recompile any package before switching to a whole new intercommunication architecture.

To get a more precise idea on how these YAML files have to be filled and which fields they require in order to succesfully configure and launch an Integration Service project, please refer to the dedicated configuration section of the official documentation.

Regarding the Fast DDS System Handle, there are several specific parameters which can be configured for the DDS middleware. All of these parameters are optional, and fall as suboptions of the main five sections described in the Configuration chapter of the Integration Service repository:

systems: The system type must be fastdds. In addition to the type and types-from fields, the Fast DDS System Handle accepts the following specific configuration fields:
```
systems:
 dds:
 type: fastdds
 participant:
 domain_id: 3
 file_path: <path_to_xml_profiles_file>.xml
 profile_name: fastdds-sh-participant-profile
```
- participant: Allows to add specific configuration for the Fast DDS DomainParticipant:
 - domain_id: Provides an easy way to change the Domain ID of the DDS entities created by the Fast DDS System Handle.
 - file_path: Path to an XML file, containing a configuration profile for the System Handle participant. More information about Fast DDS XML profiles and how to fully customize the properties of DDS entities through them is available here.
 - profile_name: Within the provided XML file, the name of the XML profile associated to the Integration Service Fast DDS System Handle participant.

Examples

There are several Integration Service examples using the Fast DDS System Handle available in the project's main source code repository.

Some of these examples, where the Fast DDS System Handle plays a different role in each of them, are introduced here.

DDS - ROS 2 bridge (publisher - subscriber)

In this example, Integration Service uses both this Fast DDS System Handle and the ROS 2 System Handle to transmit data coming from a Fast DDS publisher into the ROS 2 data space, so that it can be consumed by a ROS 2 subscriber on the same topic, and viceversa.

The configuration file used by Integration Service for this example can be found here.

For a detailed step by step guide on how to build and test this example, please refer to the dedicated section in the official documentation.

DDS service server

In this example, the Fast DDS System Handle tackles the task of bridging a DDS server with one or more client applications, playing the role of a service server capable of processing incoming requests from several middlewares (ROS1, ROS2, WebSocket) and producing an appropriate answer for them.

The configuration file used by Integration Service for this example can be found here.

For a detailed step by step guide on how to build and test this example, please refer to the dedicated section in the official documentation.

DDS Domain ID change

In this example, Integration Service uses the Fast DDS System Handle to forward the messages sent from a DDS publisher hosted on a participant with domain ID 5 to a subscriber created under domain ID 3.

The configuration file for this example can be found here.

For a detailed step by step guide on how to build and test this example, please refer to the dedicated section in the official documentation.

WAN-TCP tunneling over DDS

The last example depicts how Integration Service, along with the Fast DDS System Handle, could be useful to forward the messages coming from a ROS 2 node running on a certain machine to another ROS 2 node running on another machine, which are connected to two separate WAN networks, thanks to the WAN capabilities of Fast DDS.

The configuration files for this example can be found here.

For a detailed step by step guide on how to build and test this example, please refer to the dedicated section in the official documentation.

Compilation flags

Besides the global compilation flags available for the whole Integration Service product suite, there are some specific flags which apply only to the Fast DDS System Handle; they are listed below:

BUILD_FASTDDS_TESTS: Allows to specifically compile the Fast DDS System Handle unitary and integration tests; this is useful to avoid compiling each System Handle's test suite present in the colcon workspace, which is what would happen if using the BUILD_TESTS flag; and thus, minimizing the building time; to use it,after making sure that the Fast DDS System Handle is present in the colcon workspace, the following command must be executed:
```
~/is_ws$ colcon build --cmake-args -DBUILD_FASTDDS_TESTS=ON
```

Documentation

The official documentation for the Fast DDS System Handle is included within the official Integration Service documentation, hosted by Read the Docs, and comprises the following sections:

License

This repository is open-sourced under the Apache-2.0 license. See the LICENSE file for more details.

Getting help

If you need support you can reach us by mail at support@eProsima.com or by phone at +34 91 804 34 48.