Flask web app not responding to external requests on EC2

Found this question while searching for a solution to the same issue.

edit run.py to enable flask to respond to requests from other than localhost.this example enables responding to requests from anywhere. good security policies would use something more restrictive.

app.run(host='0.0.0.0')

in aws control panel go to EC2 : select instance.

browser should be pointed to the address from 'Public DNS (IPv4)'(the ip# from IPv4 Public IP might also be useful)

look for 'Security groups' : right click to open the security group on new page.

check inbound rules.

by default flask binds to port 5000. add rule permitting incoming tcp traffic on port 5000.

while good security protocol should limit the number of ports left open and the range of IP's permitted to connect, it might be easier to permit 'anywhere' to connect over 'all tcp'.

NB : check if the default port has been changed in the flask config file run.py

ie: line below changes port from the default 5000 to 3000.app.run(debug=True, port=3000)

Can also check if the flask instance is working locally by ssh'ing to server and using a local instance of the lynx text browser to verify the port is responding. ie

lynx localhost:5000

Was able to ultimately answer my own question, both really

The problem I was having on AWS was that my inbound for that EC2 was not allowing access through the ports that I would need.

When I tried running it on my local machine at work, firewall settings change the address of localhost (and my IP) so that's why I couldn't access it outside of using localhost:5000

In your EC2 instance, the security group is what restricting your entry to the website.

• Go to AWS portal, select your instance
• Locate the security group and click the name
• in the inbound rule window, select add rule
• Not a recommended security practice but to get it running, select All TCP
• add '0.0.0.0' in the source

your website will be running