# rosbridge.md

## **rosbridge\_server**

"Rosbridge server creates a WebSocket connection and passes any JSON messages from the WebSocket to rosbridge\_library, so rosbridge library can convert the JSON strings into ROS calls..." (to read more, see the [rosbridge\_server documentation](http://wiki.ros.org/rosbridge_server))

## **roslibpy**

"Python ROS Bridge library allows to use Python and IronPython to interact with ROS, the open-source robotic middleware. It uses WebSockets to connect to rosbridge 2.0 and provides publishing, subscribing, service calls, actionlib, TF, and other essential ROS functionality..." (to read more, see the [roslibpy documentation](https://roslibpy.readthedocs.io/en/latest/))

## **installation**

to install rosbridge\_server and roslibpy:

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

`pip install roslibpy`

## **the code**

```
import roslibpy

client = roslibpy.Ros(host='localhost', port=9090)
client.run()

pub = roslibpy.Topic(client, topic_name, message_type)

pub.publish(roslibpy.Message(message_data))

pub.unadvertise()
client.terminate()
```

## **json format**

a json file with the format shown below where

```
"command": { 
    "receiver": "/cmd_vel",
    "type": "geometry_msgs/Twist",
    "msg" : {
        "linear": {
            "x": 0.0,
            "y": 0.0,
            "z": 0.0
        },
        "angular": {
            "x": 0.0,
            "y": 0.0,
            "z": 0.0
        }
    }
}
```

## **to run**

```
roslaunch rosbridge_server rosbridge_websocket.launch

rosrun package_name node_name.py
```