Streamlit requests.post() raises ConnectionError 10054 - Connection Reset by Peer in Flask API

Question

I am working on a Streamlit frontend that communicates with a Flask backend running locally. The goal is to send a POST request from Streamlit to Flask using requests.post(), but I keep getting the following ConnectionError:

python

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ConnectionError: ('Connection aborted.', ConnectionResetError(10054, 'An existing connection was forcibly closed by the remote host', None, 10054, None))

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System Information:

• OS: Windows 10

• Python Version: 3.8

• Frameworks Used: Flask, Streamlit, requests

• Localhost URL: http://127.0.0.1:5000/generate-plan

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What I Expected to Happen

• Streamlit sends a POST request to http://127.0.0.1:5000/generate-plan

• Flask receives the request and returns a JSON response

• Streamlit displays the AI-generated fitness plan

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What Actually Happens

• Clicking the "Generate Plan" button in Streamlit causes the request to fail

• Flask does not log any request, indicating the request might not be reaching the server

• The error ConnectionResetError (10054) suggests the connection was forcibly closed by the host (Flask)

I am working on a Streamlit frontend that communicates with a Flask backend running locally. My goal was to send a POST request from Streamlit to Flask using requests.post().

What I Tried

1. Started Flask Backend (app.py)

   bash
   

   python app.py

   • Flask started successfully and showed:

     csharp
     

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     * Running on http://127.0.0.1:5000

2. Ran Streamlit Frontend (frontend.py)

   bash
   

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   streamlit run frontend.py

   • The UI loaded correctly, but when I clicked "Generate Plan", I received an error.

What I Expected

• Clicking "Generate Plan" should send a request to http://127.0.0.1:5000/generate-plan

• Flask should process the request and return a 7-day AI-powered fitness plan

• Streamlit should display the generated plan without issues

What Actually Happened

• Error 10054: Connection aborted. The remote host forcibly closed the connection.

• Flask did not receive the request (No logs appeared in the Flask console)

• Tried the API manually using curl and Postman, but they worked fine:

  nginx
  

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  curl -X POST http://127.0.0.1:5000/generate-plan

  • It returned {"plan": "Sample AI-generated plan"}

• But requests.post() from Streamlit failed every time.

Questions

• Why is the request failing only when made from Streamlit?

• Is this a Windows Firewall issue, Flask configuration problem, or something else?

• How can I fix this ConnectionResetError (10054)?