This example represents a minimalistic Cartesi Rollups application that simply copies (or "echoes") each input received as a corresponding output notice. This DApp's back-end is written in Python.
We can use the frontend-console application to interact with the DApp. Ensure that the application has already been built before using it.
First, go to a separate terminal window and switch to the frontend-console directory:
cd frontend-consoleThen, send an input as follows:
yarn start input send --payload "Hello there"In order to verify the notices generated by your inputs, run the command:
yarn start notice listThe payload of the notice should be "Hello there".
When developing an application, it is often important to easily test and debug it. For that matter, it is possible to run the Cartesi Rollups environment in host mode, so that the DApp's back-end can be executed directly on the host machine, allowing it to be debugged using regular development tools such as an IDE.
This DApp's back-end is written in Python, so to run it in your machine you need to have python3 installed.
In order to start the back-end, run the following commands in a dedicated terminal:
cd echo-python/
python3 -m venv .venv
. .venv/bin/activate
pip install -r requirements.txt
ROLLUP_HTTP_SERVER_URL="http://127.0.0.1:5004" python3 echo.pyThe final command will effectively run the back-end and send corresponding outputs to port 5004.
It can optionally be configured in an IDE to allow interactive debugging using features like breakpoints.
You can also use a tool like entr to restart the back-end automatically when the code changes. For example:
ls *.py | ROLLUP_HTTP_SERVER_URL="http://127.0.0.1:5004" entr -r python3 echo.pyAfter the back-end successfully starts, it should print an output like the following:
INFO:__main__:HTTP rollup_server url is http://127.0.0.1:5004
INFO:__main__:Sending finish
After that, you can interact with the application normally as explained above.