Let’s work through fixing your port access problem step by step—here are the most impactful checks and fixes to try first:

1. Confirm Your App is Listening on 0.0.0.0 Inside the Container #

This is the #1 culprit for this kind of issue! Many apps (like Django) default to listening only on 127.0.0.1 (localhost inside the container), so even if port mapping looks correct, external requests can’t reach the app.

• Run this command to check which interfaces your app is bound to:

  docker exec -it docker_web_1 netstat -tulpn
  # If netstat isn't installed, use this instead:
  docker exec -it docker_web_1 ss -tulpn
  

  Look for port 5000—if it shows 127.0.0.1:5000 instead of 0.0.0.0:5000, that’s the problem.
• For Django, fix your startup command to bind to all interfaces:
  Update your command in docker-compose.yml or Dockerfile to:

  python manage.py runserver 0.0.0.0:5000
  

  Your current command shows python manage.py ru…—it’s almost certainly missing the 0.0.0.0:5000 binding.

2. Test Access From Inside the Container #

First rule out that the app itself isn’t running properly:

• Jump into the container:

  docker exec -it docker_web_1 bash
  

• Try accessing the app locally inside the container:

  curl http://localhost:5000
  

If this fails, check the container logs for startup errors (like missing dependencies or Django migration issues):

docker logs docker_web_1

3. Check Host Firewall & Cloud Security Groups #

Your host machine’s firewall might be blocking incoming traffic on port 5000:

• If you’re using ufw (common on Ubuntu), allow the port temporarily for testing:

  sudo ufw allow 5000
  

• If you’re on a cloud server (AWS, GCP, etc.), make sure your security group has an inbound rule allowing traffic on port 5000 from your IP (or 0.0.0.0/0 for quick testing).

4. Refresh the Container & Verify Port Mapping #

Even though docker ps shows the mapping, restarting can resolve occasional glitches:

• Stop and restart your containers:

  docker-compose down && docker-compose up -d
  

• You can also add EXPOSE 5000 to your Dockerfile (it’s not strictly required for port mapping, but helps Docker recognize the intended service port).

内容的提问来源于stack exchange，提问作者Serg Bombermen