Port 443 Closed Checklist

Problem

HTTPS should be available, but externally port 443 appears closed or unreachable.

Symptoms

• Port checks show no open ports or do not show 443 as open.
• SSL checks cannot retrieve certificate data.
• Browsers time out or fail to connect over HTTPS.

Top 3 Causes

1. Firewall or security group blocks inbound 443 - External traffic is not permitted.
2. No active listener on 443 - The web server or reverse proxy is not actually listening for HTTPS.
3. Broken forwarding path - NAT, load balancer, or proxy layers do not pass 443 traffic correctly.

Diagnose with DechoNet

• Port Check to confirm whether port 443 is open from the outside.
• SSL Check to verify whether a TLS handshake can even begin.
• HTTP Check to see whether HTTP still works and how HTTPS redirects behave.

Resolution Checklist

• Confirm inbound 443 is allowed in your firewall, security group, or hosting panel.
• Verify the web server or reverse proxy is listening on port 443.
• Check whether the load balancer or proxy forwards 443 traffic to the correct origin.
• Make sure certificate deployment is not present without a working HTTPS listener.
• Re-run Port Check and SSL Check after changes.

When to Escalate

• Escalate to the network or hosting provider if a managed load balancer or firewall blocks your visibility.
• Escalate internally if a central security device controls ingress policy and you cannot modify it directly.