Turning an Android Phone into a Web Server with Termux, Ruby, Sinatra, and Puma

Every year many old Android phones become electronic waste; this tutorial demonstrates how to reuse one as a web server.

Install Termux – download the Termux terminal emulator from the Google Play Store; no additional configuration is required.

Set up SSH using Dropbear so you can access the device remotely. Run the following commands in Termux:

pkg upgrade
pkg install dropbear

Set a password for SSH access:

passwd
New password:
Retype new password:
New password was successfully set.

Optionally install a terminal multiplexer for easier session management:

pkg install tmux

Test the connection from a desktop or laptop:

ssh android-ip-address -p 8022

Configure a static IP address on the phone’s Wi‑Fi settings by disabling DHCP and assigning a fixed address, preventing the router from changing it frequently.

Install Ruby, Bundler, Sinatra, and Puma – these provide a lightweight web application framework and server:

pkg install ruby
gem install sinatra puma

Install nginx to act as a reverse proxy and static file server:

pkg install nginx

Copy a suitable nginx.conf (e.g., from https://gist.github.com/ctalkington/4448153) and set appdir to the directory of your Sinatra application, such as /data/data/com.termux/files/home/android-sinatra .

Set up port forwarding on your router so external requests reach the Android web server; the exact steps depend on the router model.

Configure Dynamic DNS (DDNS) to handle a changing public IP address. Services like No‑IP provide a static domain name that updates automatically.

Run a Hello World app to verify the server is working.

Load testing can be performed with siege to simulate concurrent users; the example shows the server handling three concurrent connections.

Security considerations – keep all software up to date, monitor access logs, and follow nginx hardening guides to protect the server from malicious traffic.