Ubuntu环境下部署Flask SSL服务器：Nginx与Gunicorn通信异常及域名访问超时问题求助

Let's break down and fix your issue step by step — the timeout error points to a few clear areas we can check and resolve quickly.

1. Fix the Port Mismatch (Immediate Quick Win) #

Looking at your configs, there's a critical mismatch:

• Your Nginx config forwards traffic to http://127.0.0.1:8000
• But you're running your Flask test app on port 5000

Nginx is trying to talk to a port where nothing's listening, which is a big part of the problem. Fix this in one of two ways:

• Option 1: Update your Flask code to use port 8000

  if __name__ == "__main__":
      app.run(host="0.0.0.0", port=8000, debug=True)
  

  Then restart your Flask app with python3 test.py.
• Option 2: Update Nginx to forward to port 5000
  Edit your /etc/nginx/sites-enabled/flask_app file, change:

  proxy_pass http://127.0.0.1:8000;
  

  to:

  proxy_pass http://127.0.0.1:5000;
  

  Then validate the Nginx config and restart:

  sudo nginx -t
  sudo systemctl restart nginx
  

2. Open Firewall & Cloud Security Group Ports #

ERR_CONNECTION_TIMED_OUT almost always means external traffic can't reach your server's 80 (HTTP) and 443 (HTTPS) ports.

Check Ubuntu's UFW Firewall #

• List current rules: sudo ufw status
• If 80/tcp and 443/tcp aren't allowed, add them:

  sudo ufw allow 80/tcp
  sudo ufw allow 443/tcp
  sudo ufw reload
  

Check Cloud Provider Security Groups #

If you're using a cloud server (AWS, GCP, Azure, etc.), don't forget to update your security group/network ACL to allow inbound traffic on ports 80 and 443. This is one of the most commonly missed steps!

3. Validate Nginx is Running Correctly #

Even if your config looks right, confirm Nginx is working as expected:

• Check config syntax for errors: sudo nginx -t (fix any reported issues immediately)
• Check Nginx status: sudo systemctl status nginx — it should show active (running)
• Inspect logs for clues:

  sudo tail -f /var/log/nginx/error.log
  sudo tail -f /var/log/nginx/access.log
  

4. Switch to Gunicorn for Production (Recommended) #

You're using Flask's built-in development server, which isn't designed for production use. Since you mentioned Gunicorn, let's set that up properly:

Step 1: Install Gunicorn #

pip3 install gunicorn

Step 2: Run Flask with Gunicorn on Port 8000 #

gunicorn --bind 127.0.0.1:8000 test:app

Here, test is your Python filename (test.py), and app is your Flask instance name.

Step 3: Set Up Gunicorn as a Systemd Service (Auto-Start on Boot) #

Create a service file to keep Gunicorn running in the background:

sudo nano /etc/systemd/system/flask_app.service

Add this content (replace placeholders with your actual username and app directory):

[Unit]
Description=Gunicorn instance for Flask chatbot app
After=network.target

[Service]
User=your_username
Group=www-data
WorkingDirectory=/path/to/your/app/folder
ExecStart=/usr/bin/gunicorn --workers 3 --bind 127.0.0.1:8000 test:app

[Install]
WantedBy=multi-user.target

Then start and enable the service:

sudo systemctl start flask_app
sudo systemctl enable flask_app
sudo systemctl status flask_app

5. Rule Out Certificate Issues (Less Likely for Timeouts) #

Your timeout error isn't typical of certificate problems (cert issues usually throw SSL/TLS-specific errors like NET::ERR_CERT_INVALID). But to be thorough:

• Verify your Certbot certificate is valid:

  sudo certbot certificates
  

  If it shows Status: Valid, your certificate is working fine.

Final Checks #

After making these changes:

• Confirm your app is listening on port 8000: sudo lsof -i :8000 (you should see the Gunicorn/Flask process)
• Test connectivity from an external machine: curl -v https://viberchatbot.ga or use telnet viberchatbot.ga 443 to see if the connection can be established.

内容的提问来源于stack exchange，提问作者i.svirchev