May 31, 2026 · Web Servers · 1min read

Tornado Local Python Web Development Guide

Run Python applications on localhost using the Tornado asynchronous web framework, defaulting to http://localhost:8888.

Tornado is an asynchronous web framework and HTTP server for Python, suitable for long connections, WebSocket, and high-concurrency I/O. It comes with a built-in HTTP server, eliminating the need for additional Apache/Nginx for local development.

Default localhost Access

Purpose	Address
Common example default	http://localhost:8888
Custom port	Specified by `listen()` in code

The official Tornado example commonly uses port 8888 (not mandatory, can be specified as needed).

Minimal Example

import tornado.ioloop
import tornado.web

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        self.write("Hello from localhost")

app = tornado.web.Application([(r"/", MainHandler)])
app.listen(8888)
tornado.ioloop.IOLoop.current().start()

After running, access http://localhost:8888.

Installation

pip install tornado

WebSocket

Tornado natively supports WebSocket, and during local debugging, the frontend connects to paths like ws://localhost:8888/ws.

Frequently Asked Questions

Port Occupied
Change to another port with app.listen(9090) or similar.

Conflict with Jupyter
Jupyter also commonly uses port 8888; do not occupy the same port simultaneously.

Summary

Tornado’s built-in server allows local development access at http://localhost:8888 (or the port configured in the code).