2022-12-30 ROS Bridge Installation

In order to Alarm Watchdog app to connect to ROS controlled drone you need to install ROS package and run it on the drone itself.

ROS Package

On ROS node must be installed rosbridge-server package

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sudo apt-get install ros-noetic-rosbridge-server

Instead on noetic use current ROS package rosversion -d name.

Need to also install few python3 libraries

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pip3 install rospkg autobahn 
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pip3 install pymongo[bson]

Then rosbridge web-socket server can be configured in file:

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cat /opt/ros/noetic/share/rosbridge_server/launch/rosbridge_websocket.launch

By default it has 9090 port, but it can be changed and also some authorization can be added if needed.

Firewall

Before launching service should open firewall to port

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 sudo apt install firewalld firewall-config
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 sudo firewall-cmd --zone=public --add-port=9090/tcp --permanent 
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 sudo firewall-cmd --reload
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 sudo ufw allow 9090

Then test it, server side using netcat. This is done on Server/ROS node

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 nc -l 9090

Client side using telnet (replace IP by server IP) This is done on some other Linux/Mac machine in network

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 telnet IP 9090

^ if you can send messages over network then ports are ok, if not then some firewall is preventing it

Launching service

Best would be to to create permanent linux service, but for more control we advice initially to run rosbridge in linux background screen

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screen -S rosbridge

Then to launch rosbridge service on ROS node:

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source /opt/ros/noetic/setup.bash
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screen -S rosbridge
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roslaunch rosbridge_server rosbridge_websocket.launch

^This will then start running and you can detach from screen

Screens:

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screen -ls     (List all of the screen sessions for a user)
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screen -rd ...(name of screen to log into)...
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screen -S ...(new screen name)...

Console management:

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Ctrl+A D   (exit screen, program will continue to  run)
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Ctrl+A K   (kill a screen)

Send test ROS topic from console

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rostopic pub -1 /test_topic std_msgs/String "Hello World"