Hey now we will learn about the ros nodes So ros node is a modular identity that can have publisher 2
subscriber services and parameters for 3
example if a person is a Node it can hear it means it is subscribing and it can speed 4
publishing let's learn more about the ros nodes here is an illustration that explains the ros nodes 5
and here you can see the nodes in the circle there are three Nodes and they 6
are communicating over the topic and there's a service So currently do not know the service so you 7
do not need to spend much time over to it we will learn these things in the future 8
ros2 node list here is the command that will list all the active nodes 9
and currently we have just one active node we will open up another terminal and uh 10
so here we have another node let's see again the list 11
teleop turtle and the turtlesim now we have two nodes let's monitor their connection using rqt_graph 12
here we can select all and 13
here are the node and there connection between them we can select here nodes only and refresh and 14
there you will see a simpler illustration do you remember previously we used the remap keyword 15
uh we use it to remap a topic now we will remap a node so Ros 2 run turtlesim 16
underscore node minus minus Ros minus args minus remap and what we have to remap is the node 17
node colon equal and we can enter any name so let's enter 18
turtlesimbot 19
here we have another window a similar one so let's see the list of ros nodes we have 20
the three nodes right now this one new node turtlesim bot and we can also see the topic ros2 21
topic list so we have three topics that are related to the turtlesim we have two windows 22
of turtlesim but we have three topics the topics remain same because we just have changed the name 23
of the Node let's see if we can operate both turtlesim windows or with just one teleop 24
yeah they're moving absolutely they are moving to get a complete information about a node to learn 25
about it's topic subscribers publisher and the services action we can use a command ros2 26
node info and the node name we will enter 27
Turtlesim bot and it has displayed a list of different things like subscriber publisher 28
server and the client service clients and uh actual server rqt underscore graph 29
and here you can see the illustration of the connection between the nodes and the topics 30
so congratulations you have learned to basics of ros nodes 31
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