ROS WEBSOCKET BRIDGE

Overview

This is a package for converting ROS 2 DDS to WebSocket. This project was inspired by rosbridge_suite by Robo Web Tools. The implemented features are not for specific topics or services but all available ros interfaces. It's in early development, and not all interfaces are tested. Any bug reported will be fixed in upcoming releases.

When using the suite, I faced issues with ROS 2 and couldn't find a way to move forward. So I decided to create another which is not advanced as the suite but gets my job done. I decided to package it and publish it on PyPI for easy availability to others and for learning purposes. The code I use is different, and the features are not the same. The client libraries for the suite won't work because this is not a suite clone.

Note: This project is not a suite clone. The architecture and implementation are different. Not all the features of the suite are not available in this project.

Requirements

• Ubuntu 20.04
• Python 3.8
• ROS 2 Foxy

Installation

pip3 install ros2bridge

Usage

python3 -m ros2bridge

optional parameters:

• -p, --port: For specific port. Default is 9020
• -n, --ngrok: WebSocket is hosted on local IP by default. If this flag is set ws are hosted internally

NOTE: for using custom ros interface source that workspace before running the bridge.

Available ROS Interfaces

• Publisher
• Subscriber
• Service Client
• Action Client

TODO:

• Service Server
• Action Server

Request structure

Publisher

{
    "operation": "publish",
    "topic": "/<topic_name>",
    "type": "<message_parent>/<message_type>",
    "message": "<message>"
}

• type eg: 'std_msgs/String'
• message eg: {"data": "HELLO WORLD !"}
• NOTE: the message should be in the format of the message type

Subscriber

{
    "operation": "subscribe",
    "topic": "/<topic_name>",
    "type": "<message_parent>/<message_type>",
}

• type eg: 'std_msgs/String'

NOTE: Subscribed messages will return in this format.

{
    "operation": "subscribe",
    "topic": "/<topic_name>",
    "type": "<message_parent>/<message_type>",
    "message": "<message>"
}

• type eg: 'std_msgs/String'
• message eg: {"data": "HELLO WORLD !"}

NOTE: To unsubscribe from a topic send the following message to the server

{
    "operation": "subscribe",
    "topic": "/<topic_name>",
    "type": "<message_parent>/<message_type>",
    "unsubscribe": true
}

• type eg: 'std_msgs/String'

SERVICE CLIENT

For creating a service client

{
    "operation": "srv_client",
    "action": "create",
    "srv_name": "/<service_name>",
    "srv_type": "<service_parent>/<service_type>"
}

For calling a service client

{
    "operation": "srv_client",
    "action": "call",
    "srv_name": "/<service_name>",
    "srv_type": "<service_parent>/<service_type>",
    "message": "<message>"

}

• NOTE: the message should be in the format of the service type

ACTION CLIENT

For creating an action client

{
    "operation": "action_client",
    "action": "create",
    "action_name": "/<action_name>",
    "action_type": "<action_parent>/<action_type>"
}

For calling an action client

{
    "operation": "action_client",
    "action": "call",
    "action_name": "/<action_name>",
    "action_type": "<action_parent>/<action_type>",
    "message": "<message>"
}

• NOTE: the message should be in the format of action type

Feedback from calling an action client

{
    "operation": "action_client",
    "action": "call",
    "action_response": "<action_response>",
    "action_name": "/<action_name>",
    "action_type": "<action_parent>/<action_type>",
    "message": "<message>"

}

• NOTE: the message should be in the format of action type.
• NOTE: action_response will be any of 'response', 'feedback', or 'result'.

QOS PROFILE

I added a QoS profile to the subscription. No validation of QoS is added and no error is sent back to the client.

Available QoS settings for subscribers:

• QoSReliabilityPolicy
• QoSDurabilityPolicy
• QoSHistoryPolicy

For creating a Qos Profile add the following in addition to the above request syntax

"qos": {
    "durability": "<durability>",
    "reliability": "<reliability>",
    "history": "<history>",
}

For options to provide please refer to this docs

A general request will look like

{
    "operation": "subscribe",
    "topic": "/<topic_name>",
    "type": "<message_parent>/<message_type>",
    "qos": {
        "durability": "<durability>",
        "reliability": "<reliability>",
        "history": "<history>",
    }
}

Testing

For testing using tox, the ROS package is required and I haven't found a way to get around it. So testing within the system.

• MYPY
• FLAKE8
• PYTEST