materiallogindemo | Android login and signup demo with material design | Android library

You are sending the request as "POST" from your Android application but on Python side, the route you created will accept "GET".

@app.route('/a/', methods=['GET'])

conn.setRequestMethod("POST");

Try changing @app.route('/a/', methods=['GET']) with @app.route('/a/', methods = ['POST'])

Also seems like you are trying to connect to HTTPS:

URL url = new URL("https://192.168.43.31:5000/a/");

Try creating the app instance like below: if __name__ == '__main__': app.run(port=5000, host='0.0.0.0', debug=True, ssl_context='adhoc')

pip install pyopenssl