- Serve it over HTTPS only and check the HTTP security headers.
- Keep admin consoles and development servers off the Internet.
- Patch the application server and remove default credentials and sample apps.
Port 591: FileMaker, Inc. - HTTP Alternate (see Port 80)
Port 591 is assigned by IANA to http-alt (FileMaker, Inc. - HTTP Alternate (see Port 80)).
591
How http-alt works
WebA browser sends an HTTP request to port 591 and the http-alt server sends the page back.
- Transport
- TCP · UDP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Well-known (0-1023)
- Category
- Web
Is port 591 dangerous?
We have no specific security note for port 591. Its risk depends on the program actually listening on it. General advice for web services:
IANA registry entries for port 591
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| http-alt | 591 | TCP, UDP | FileMaker, Inc. - HTTP Alternate (see Port 80) | - | - |
// source: IANA service name and port number registry
Which program uses port 591, and is it reachable?
Linux
sudo ss -ltnup 'sport = :591' # process listening on 591
sudo lsof -nP -i :591macOS
sudo lsof -nP -i :591
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 591 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 591 netstat -ano | findstr :591
From another machine
nmap -p 591 -sV <host> sudo nmap -sU -p 591 <host> nc -zv <host> 591
Block it in the firewall
sudo ufw deny 591/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 591" -Direction Inbound -LocalPort 591 -Protocol TCP -Action Block # Windows
What is port 591 used for?
Port 591 is assigned by IANA to http-alt (FileMaker, Inc. - HTTP Alternate (see Port 80)).
Is port 591 TCP or UDP?
Port 591 is registered for TCP and UDP.
Is it safe to open port 591?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Serve it over HTTPS only and check the HTTP security headers.
How do I check if port 591 is open?
On Linux run "ss -ltnup 'sport = :591'", on macOS "lsof -nP -i :591", and on Windows "netstat -ano | findstr :591" to see the local process. From another machine, "nmap -p 591 <host>" shows whether it is reachable.
Other web ports
:443 HTTPS tcp · udp · sctp · low risk :80 HTTP tcp · udp · sctp · moderate risk :8080 HTTP alternate tcp · udp · high risk :8443 HTTPS alternate tcp · udp · moderate 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