ROS2 Communication
ROS2 (DSS) uses a discovery mechanism to communicate between the nodes. By default this will allow all computers in the same network as the robot to discover the ROS2 nodes. This might not be usefull in an educational setup. Therefore there are three setups you can use on the MIRTE robot:
Type |
Discovery |
Useful setup |
|---|---|---|
localhost (MIRTE default) |
Only on the robot |
All robots on the same network, but no need to use ROS from another machine |
zenoh |
Only those who set zenoh conf |
All robots on the same network, and want to use ROS from another machine |
full (ROS2 default) |
All in network |
Just one robot on the network (or AP version) |
These settings are mostly useful in a router setup, but is also good to know in a setup where the robot acts as the access point (AP). The default in MIRTE is localhost. In that way users not using ROS (eg secondary school MIRTE Pioneer teachers) can easily connect all MIRTE robots to the same network. This default might only be not the preferred way for the more advanced users. They should be able to modify the settings to their needs.
The settings are stored in ~/.mirte_settings.sh. These are already sourced in your ~/.bashrc, and also sourced when starting the mirte-ros systemd service. After changing these settings, you should restart the mirte-ros service, and open a new terminal. Or just reboot.
In this setup, only the robot itself is able to discover nodes.
On the MIRTE robot in ~/.mirte_settings.sh:
export MIRTE_ZENOH=false
export ROS_LOCALHOST_ONLY=1
For this to take effect, you need to restart ROS.
This is a setup comparable with the ROS master in ROS1.
On the MIRTE robot in ~/.mirte_settings.sh:
export MIRTE_ZENOH=true
export ROS_LOCALHOST_ONLY=0
For this to take effect, you need to restart ROS. And on your own machine, you should have the mirte-zenoh-setup package installed (which should install ros-humble-rmw-zenoh-cpp when using rosdep), and start it with:
$ ros2 run rmw_zenoh_cpp rmw_zenohd
And in another terminal source your workspace with the right IP address:
$ export MIRTE_ZENOH=<mirte_ip>
$ source install/setup.bash
This is the default setup for a fresh ROS2 installation.
On the MIRTE robot in ~/.mirte_settings.sh:
export MIRTE_ZENOH=false
export ROS_LOCALHOST_ONLY=0
For this to take effect, you need to restart ROS.