Fly.io

Fly.io has robust WebSocket support and can deploy your app to a data center that is close to your users. They have very attractive pricing with a generous free tier which allows you to host up to 3 applications for free.

To get started with Fly install flyctl and then authenticate:

flyctl auth login

To deploy the app with flyctl you have to add the following 3 files into the folder with your Python app.

Create requirements.txt with a list of application dependencies. At minimum it should contain flet module:

requirements.txt

flet

Create fly.toml describing Fly application:

fly.toml

app = "<your-app-name>"

kill_signal = "SIGINT"
kill_timeout = 5
processes = []

[env]
  FLET_SERVER_PORT = "8080"

[experimental]
  allowed_public_ports = []
  auto_rollback = true

[[services]]
  http_checks = []
  internal_port = 8080
  processes = ["app"]
  protocol = "tcp"
  script_checks = []

  [services.concurrency]
    hard_limit = 25
    soft_limit = 20
    type = "connections"

  [[services.ports]]
    force_https = true
    handlers = ["http"]
    port = 80

  [[services.ports]]
    handlers = ["tls", "http"]
    port = 443

  [[services.tcp_checks]]
    grace_period = "1s"
    interval = "15s"
    restart_limit = 0
    timeout = "2s"

Replace <your-app-name> with desired application name which will be also used in application URL, such as https://<your-app-name>.fly.dev.

Note we are setting the value of FLET_SERVER_PORT environment variable to 8080 which is an internal TCP port Flet web app is going to run on.

Create Dockerfile containing the commands to build your application container:

Dockerfile

FROM python:3-alpine

WORKDIR /app

COPY requirements.txt ./
RUN pip install --no-cache-dir -r requirements.txt

COPY . .

EXPOSE 8080

CMD ["python", "./main.py"]

main.py is a file with your Python program.

note

Fly.io deploys every app as a Docker container, but a great thing about Fly is that it provides a free remote Docker builder, so you don't need Docker installed on your machine.

Next, switch command line to a folder with your app and run the following command to create and initialize a new Fly app:

flyctl apps create --name <your-app-name>

Deploy the app by running:

flyctl deploy

That's it! Open your app in the browser by running:

flyctl apps open