Please help as I have landed into a trouble with my flask server for pset8/mashup. Per the spec within mashup/ I execute pip install --user -r requirements.txt and then in a terminal window I execute export API_KEY=value (value from credentials in my console). I have made two API keys though I use one of them. Then in mashup/ I execute flask run and then in another terminal within mashup/ I execute phpliteadmin mashup.db. After this when I go to CS50 IDE>Web Server I get a webpage saying "no application seems to be running here". Flask was showing the following messges : * Serving Flask app "application" * Forcing debug mode on * Running on (Press CTRL+C to quit) * Restarting with stat * Debugger is active! * Debugger PIN: 270-621-200

"Running on (Press CTRL+C to quit)" seems relevant as it is serving PORT 5000 which I guess should be 8080 for my application to run. But I am too naive to do this. So, plse tell me how to resolve this issue to get my CS50 IDE server run my application.

1 Answer 1


Change the call from flask run to flask run --host= --port=8080 and it should work, as per this reddit post.

  • Thanks, buddy, you are a true genius! I was almost clueless how my server would work but now this is resolved. In fact, I did notice that David used the above code to run flask in some of the applications of week8 and week9 lectures but didn't pay attention then. Anyway, thanks again.
    – sk.76
    Commented Aug 2, 2017 at 11:19
  • I have the same error but my output says: * Running on ide50-chrisdziewa1.c9users.io:5000 I tried the above fix and it still isn't working. Any ideas? It was working fine yesterday.
    – razzdango
    Commented Aug 2, 2017 at 23:27
  • @razzdango According to the cs50 status page this was fixed with a new IDE version (update50). Commented Aug 3, 2017 at 11:34
  • @razzdango do u execute update50 before running flask?
    – sk.76
    Commented Aug 3, 2017 at 11:43

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