* ros2 command line utility works well on emulator:
root@qemux86:~# ros2 topic list
/parameter_events
/rosout
root@qemux86:~# ros2 topic pub /chatter std_msgs/String "data: Hello world"
publisher: beginning loop
publishing #1: std_msgs.msg.String(data='Hello world')
publishing #2: std_msgs.msg.String(data='Hello world')
^C
root@qemux86:~# ros2 topic echo /chatter
data: Hello world
data: Hello world
^C
* Version-specific because it might be fixed in a new version.
Andre Rosa