Q1: What does it mean when a port is "closed"?
When a scanning site reports a port as "closed", it means:
- There is no software listening on that port.
- Or, your firewall or cloud provider is rejecting connection attempts.
A closed port responds with "connection refused" — it exists, but no program is accepting connections.
At hostdare we have tcp ports open , but udp is blocked in some VPS plans .
Q2: Why would a port be closed on my server?
Typical reasons include:
1. No Software/application is running on that port.
2. The service crashed or is misconfigured.
3. Firewall rules block it.
4. Your app is listening only on localhost (127.0.0.1), not public IP.
Q3: I expected the port to be open. What should I check?
Step 1: Check if something is listening
Run this in terminal:
sudo ss -tuln | grep :PORT
Replace PORT with your desired port number (e.g., 8080).
Step 2: Check your firewall rules
If using iptables:
sudo iptables -L -n
If using UFW:
sudo ufw status
Q4: Why do some sites say "filtered" instead of "closed"?
- "Closed": Server actively rejects connection.
- "Filtered": Server (or firewall) drops the request silently — no response.
Q5: Is a closed port bad?
No. If you're not using the port, it’s good that it’s closed — it's secure.
If it should be open, confirm:
- The service/Software/Application is running and bound to the correct IP.
- Firewall allows it.
Q6: How do I open a port?
You open a port by starting an app that listens on it.
Example:
1. Start your service (like a web app on port 8080).
2. Make sure it binds to 0.0.0.0 or your public IP.
3. Allow the port in firewall:
sudo ufw allow 8080
Q7: How can I check all open ports and running services?
Run:
sudo ss -tuln
Or:
sudo lsof -i -P -n | grep LISTEN
Q8. My Ports shows blocked in china , but open worldwide. what to do ?
Please open a support ticket if your port is blocked in china but open worldwide
But if your IP is blocked worldwide including china , you need to check your settings as told before .
