Tech Monger

Building Simple Flask Web Application

We will create simple Hello Localtunnel application with following flask code.

web_app.py

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello Localtunnel"

if __name__ == "__main__":
    app.run()

Local Deployment with Gunicorn

We will need full fledged web server to host flask application because development server werkzeug will not able to handle too many requests. If you are just exploring this hosting option then you can skip gunicorn deployment and go ahead by deploying app with default flask web server werkzeug.

Install Gunicorn

pip install gunicorn

Deploy WSGI instance with Gunicorn

gunicorn -b 127.0.0.1:8080 web_app:app

With above command flask application will run on default port 8080 with gunicorn as web server.

Host Web Application with Localtunnel

Once your web server started serving web application on local computer you can expose it publicly with localtunnel.

If you have not already installed localtunnel client first Install Localtunnel. Note that localtunnel is available on all platform including windows.

Use following client command to expose web application on default localtunnel server at localtunnel.me.

lt -p [source-port] -s [subdomain]

source port is the port on which your web application is running.
subdomain is the name that you would like to host your app with localtunnel.me.

For example below command will expose application running locally on port 8080 with name awesomeapp at awesomeapp.localtunnel.me.

lt -p 8080 -s awesomeapp

Note that this subdomain for app will be freely provided and same will be printed on command line output.

Localtunnel server will make use of HOST header in HTTP request to identify your web application from other apps hosted at localtunnel.me.

If you want to get familiar with other localtunnel client commands then you can read localtunnel client commands and options.