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// Web

Port 8443: HTTPS alternate

Alternate HTTPS port, often used by admin consoles, appliances and application servers.

https-alt
8443

How HTTPS alternate works

Web
browser:8443#%&@!x9? browser:8443#%&@!x9?

A browser sends an HTTP request to port 8443 and the HTTPS alternate server sends the page back. Everything is encrypted: someone on the path only sees unreadable bytes.

Transport
TCP · UDP
Exposure risk
5/10 moderate if reachable from the Internet
Encryption
EncryptedTLS or built-in crypto
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Web
01 Security

Is port 8443 dangerous?

Common attacks and weaknesses

  • Admin interfaces of firewalls, VPNs and hypervisors, frequent targets of critical CVEs.
  • Default credentials.

How to secure it

  • Restrict management interfaces to admin networks.
  • Patch appliances quickly.
02 Registry

IANA registry entries for port 8443

ServicePortTransportDescriptionReferenceUpdated
pcsync-https 8443 TCP, UDP PCsync HTTPS - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 8443, and is it reachable?

Linux

sudo ss -ltnup 'sport = :8443'      # process listening on 8443
sudo lsof -nP -i :8443

macOS

sudo lsof -nP -i :8443

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 8443 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 8443
netstat -ano | findstr :8443

From another machine

nmap -p 8443 -sV <host>
sudo nmap -sU -p 8443 <host>
nc -zv <host> 8443

Block it in the firewall

sudo ufw deny 8443/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 8443" -Direction Inbound -LocalPort 8443 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 8443 used for?

Alternate HTTPS port, often used by admin consoles, appliances and application servers.

Is port 8443 TCP or UDP?

Port 8443 is registered for TCP and UDP. In practice the service mostly uses TCP.

Is it safe to open port 8443?

It is rated 5/10 (moderate) when exposed to the Internet. Admin interfaces of firewalls, VPNs and hypervisors, frequent targets of critical CVEs. Restrict management interfaces to admin networks.

How do I check if port 8443 is open?

On Linux run "ss -ltnup 'sport = :8443'", on macOS "lsof -nP -i :8443", and on Windows "netstat -ano | findstr :8443" to see the local process. From another machine, "nmap -p 8443 <host>" shows whether it is reachable.

05 Related
:443 HTTPS tcp · udp · sctp · low risk :80 HTTP tcp · udp · sctp · moderate risk :8080 HTTP alternate tcp · udp · high risk :3000 Dev servers / Grafana tcp · udp · moderate risk :5000 Flask / Docker registry / UPnP tcp · udp · moderate risk :8000 HTTP alternate (dev) tcp · udp · moderate risk :8888 Jupyter / HTTP alternate tcp · udp · high risk :9443 HTTPS alternate (admin) tcp · udp · moderate risk

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