2. Installing the Connext RMW

There are multiple vendor-specific implementations of the ROS 2 RMW API, including Connext. (See https://docs.ros.org/en/kilted/Installation/RMW-Implementations.html.) This chapter describes how to install the Connext RMW.

Installing the Connext RMW for ROS 2 involves three basic steps:

Install ROS 2.
Install Connext.
Install the Connext RMW.

2.1. Version Compatibility

Each ROS 2 version is built and tested with a specific Connext version to ensure functional and ABI compatibility. Using the versions in the table below guarantees that all libraries and tools work together as intended.

Table 2.1 ROS 2 and Connext Compatibility
ROS 2 Version	Connext Version
Kilted	7.3.0
Jazzy	6.0.1
Humble	6.0.1

This documentation distinguishes between:

Officially supported combinations of ROS 2 and Connext as shown in Table 2.1, tested by RTI and eligible for support.
Other combinations that may work but are not supported by RTI and are used at your own risk. Using a Connext version with a binary ROS 2 installation not shown in Table 2.1 may result in unexpected behavior.
Connext standalone applications with ROS 2, regardless of the RMW that is used. See Section 4 or Section 5.

If you need to use a different Connext version than what’s shown for the ROS 2 version in Table 2.1, you must build both ROS 2 and the Connext RMW from source to ensure compatibility. See Binary ROS 2 Packages and Connext Version.

2.2. Connext Installation Options

A Connext installation provides the libraries needed by the Connext RMW. Without a Connext installation, the Connext RMW won’t be able to find the libraries and will not work.

To install Connext for ROS 2, there are several options. The choice depends on your needs, platform, and licensing requirements. All options ultimately provide the same Connext libraries and headers, but differ in licensing, features, and installation process.

Which Connext installation option to use depends on your use case:

Table 2.2 Connext for ROS 2 - Installation Options
Option / Use Case	Pros/Cons
ROS-hosted .deb packages Typically used by the ROS 2 community	Pros Easiest option for early prototyping No RTI-provided license required Recommended for getting started Cons Very stripped-down Connext installation Non-commercial license. Not eligible for production Notes Available on Ubuntu via apt installation Provided by the ROS 2 project Includes only the Connext versions listed in Table 2.1
RTI official .deb packages Typically used by prospects or customers evaluating the Connext RMW	Pros Easy installation Complete set of Connext tools Suitable for production use Cons Requires RTI-provided license Only available for Debian-based systems via apt
RTI official .rtipkg installation (download) Typically used by RTI customers who require the full Connext DDS feature set, including security, additional transports, etc. Use the 7.3.0 installation instructions here.	Pros Full feature set for production Available for Linux, Windows, and macOS Cons Requires RTI-provided license Installed manually (unlike .deb installations, which are done with a single command)

2.3. ROS 2 and Connext RMW Installation

To run ROS 2 with the Connext RMW, you need two things:

ROS 2 itself
A Connext installation (see Connext Installation Options)

Once Connext is installed, install ROS 2 with the Connext RMW by following the official ROS 2 installation guide for your chosen distribution: for example, https://docs.ros.org/en/kilted/Installation.html.

Before you start, note that ROS 2 is available in different installation formats, and the best choice depends on your system and needs:

Binary packages:
- Debian (.deb) packages (Ubuntu systems only). This is the recommended and easiest way to get started. It uses your system’s package manager for installation.
- Binary archives (Linux and Windows systems). This is a good option if you do not have administrator privileges or prefer not to use a package manager.
Source build (available in Linux, Windows, and macOS systems). This is useful if you want to install specific packages or modify packages, or no binary packages are available for your specific platform.

2.3.1. Ubuntu AMD/ARM

This section explains how to install ROS 2 with the Connext RMW on Ubuntu, whether you are using an AMD64 or ARM64 system. It covers three main steps:

Installing ROS 2
Installing Connext
Installing the Connext RMW

2.3.1.1. ROS 2 installation

Follow the official ROS 2 instructions for your chosen installation format:

.deb packages: https://docs.ros.org/en/kilted/Installation/Ubuntu-Install-Debs.html
Binary archives: https://docs.ros.org/en/kilted/Installation/Alternatives/Ubuntu-Install-Binary.html
Source build: https://docs.ros.org/en/kilted/Installation/Alternatives/Ubuntu-Development-Setup.html

2.3.1.2. Connext installation

Once ROS 2 is installed, you need a Connext installation for the Connext RMW to work. Install Connext using any of the methods described in Connext Installation Options.

For quick prototyping without an RTI-provided license, you can install the ROS-hosted .deb package for Connext:

$ sudo apt update && sudo apt install -q -y rti-connext-dds-7.3.0-ros # Connext 7.3.0
$ sudo apt update && sudo apt install -q -y rti-connext-dds-6.0.1 # Connext 6.0.1

As with RTI official .deb packages, the installation will be located in: /opt/rti.com/rti_connext_dds-<version>/.

You can have multiple Connext installations in your system as long as you source the correct one.

If you try to use a Connext installation other than the one used to build the Connext RMW in the first place (as given in Table 2.1), the one used for building will be used by default. This mechanism is in place to avoid possible ABI incompatibilities.

If you want, at your own risk, to use a Connext installation other than given in Table 2.1, set the environment variable CONNEXTDDS_IGNORE_BUILD=1 to override the default behavior and use a different Connext installation. See Binary ROS 2 Packages and Connext Version.

2.3.1.3. Connext RMW installation

As with ROS 2, the Connext RMW also comes in multiple installation formats, described below:

.deb packages
Binary archives
Source build

If you installed ROS 2 through binary archives, the Connext RMW should already be included in the archive.

If you built ROS 2 from source and compiled every package (like the instructions indicate), the Connext RMW should then be compiled, too, and included in the installation. If you are an advanced user, you can tweak the colcon build system for more specific use cases.

The following instructions assume ROS 2 was installed using .deb packages. Examples are shown for the Kilted distribution, but you can adapt them for other versions, such as Rolling or Jazzy.

2.3.1.3.1. Debian packages

When installed through Debian (.deb) packages, ROS 2 comes with the default RMW, which is rmw_fastdds. To use any other RMW, you need to install the corresponding .deb package.

To install the Connext RMW via .deb package, use the following command:

$ sudo apt update && sudo apt install -q -y ros-kilted-rmw-connextdds

This command installs the Connext RMW package along with its dependency packages:

ros-kilted-rmw-connextdds: Package with the Connext RMW library.
ros-kilted-rmw-connextdds-common: Package that contains the common implementation of the Connext Professional RMW and the Connext Micro RMW (deprecated).
ros-kilted-rti-connext-dds-cmake-module: CMake utils to find the Connext installation.
rti-connext-dds-7.3.0-ros: ROS-hosted .deb package.

This command should install all the libraries required by the RMW in the ROS 2 installation directory.

2.3.1.3.2. Connext RMW source build

Building from source code can ensure the Connext RMW is matched to your system and installed correctly. The following instructions assume a Linux x86_64 Connext host and target, such as rti_connext_dds-7.3.0-pro-host-x64Linux.run and rti_connext_dds-7.3.0-pro-target-x64Linux4gcc7.3.0.rtipkg.

Use the following commands to clone the repository for rmw_connextdds into your ROS 2 workspace and select the branch that matches the ROS 2 distribution in use:

$ mkdir -p ros2_ws/src
$ cd ros2_ws
$ git clone -b kilted https://github.com/ros2/rmw_connextdds src/rmw_connextdds

Set up the environment to help colcon discover where RTI Connext is installed. Do this by manually setting the environment variable NDDSHOME to the location of the Connext installation, or by using a script that comes with the Connext installation:

$ source ${RTI_CONNEXT_INSTALL_LOCATION}/resource/scripts/rtisetenv_x64Linux4gcc7.3.0.bash

Make sure you have the ROS 2 environment set up:

$ source /opt/ros/kilted/setup.bash

Build the Connext RMW using colcon:

$ colcon build --symlink-install

After the build completes successfully, be sure to source the setup file for the workspace:

$ source install/setup.bash

2.3.2. Windows

On Windows systems, ROS 2 does not provide Connext binaries, so you must install Connext first. Download and install Connext following the RTI Connext Professional Installation Guide.

ROS 2 releases for Windows systems are available from the GitHub releases page: https://github.com/ros2/ros2/releases.

You can install ROS 2 in two ways:

Binary archives. Follow the official guide: https://docs.ros.org/en/kilted/Installation/Windows-Install-Binary.html. The Connext RMW is already included in the binary archive, so no separate installation is required.
ROS 2 source build. Follow the official guide: https://docs.ros.org/en/kilted/Installation/Alternatives/Windows-Development-Setup.html. When building from source, the Connext RMW will be compiled along with the rest of ROS 2.

2.3.3. Other systems

To build ROS 2 in any other environment, check the alternatives provided by the ROS 2 documentation: https://docs.ros.org/en/kilted/Installation/Alternatives.html.

2.4. Binary ROS 2 Packages and Connext Version

Each ROS 2 version (Kilted, Jazzy, etc.), when it’s a binary package, is attached to a single version of Connext. See Version Compatibility.

Providing binary packages allows ROS 2 users to get started more quickly and easily. Binary packages are normally provided in two formats:

Debian (.deb) and Red Hat (RPM) packages: These are available for specific operating systems and distributions.
Binary archives: Compressed files with all the libraries needed for ROS 2 to work, along with ROS 2-specific tools and RMWs.

While convenient, binary packages are tied to the Connext version they were built with. ROS 2 and Connext must be ABI-compatible, so replacing the installed Connext version with a different one can lead to runtime failures. For example, Kilted binaries are compiled using Connext 7.3.0. If you want to use the Connext RMW with an underlying Connext 7.5.0 installation (instead of a 7.3.0 one), the ABIs are not going to match, resulting in application crashes or unpredictable behavior.

ABI-mismatch errors can be cryptic and hard to diagnose. For that reason, if you want to use a Connext version that’s not the default one in a specific ROS 2 release, you should build the Connext RMW from source. This will ensure you are using the correct Connext libraries in the RMW.