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// Other services

Port 643: SANity

Port 643 is assigned by IANA to sanity (SANity).

643

How sanity works

Other services
client:643sanityresponse client:643sanityresponse

The client sends a request to port 643 and the sanity service answers.

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
Other services
01 Security

Is port 643 dangerous?

We have no specific security note for port 643. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 643

ServicePortTransportDescriptionReferenceUpdated
sanity 643 TCP, UDP SANity - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 643, and is it reachable?

Linux

sudo ss -ltnup 'sport = :643'      # process listening on 643
sudo lsof -nP -i :643

macOS

sudo lsof -nP -i :643

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 643 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 643
netstat -ano | findstr :643

From another machine

nmap -p 643 -sV <host>
sudo nmap -sU -p 643 <host>
nc -zv <host> 643

Block it in the firewall

sudo ufw deny 643/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 643" -Direction Inbound -LocalPort 643 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 643 used for?

Port 643 is assigned by IANA to sanity (SANity).

Is port 643 TCP or UDP?

Port 643 is registered for TCP and UDP.

Is it safe to open port 643?

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. Close the port if nothing on the host needs it.

How do I check if port 643 is open?

On Linux run "ss -ltnup 'sport = :643'", on macOS "lsof -nP -i :643", and on Windows "netstat -ano | findstr :643" to see the local process. From another machine, "nmap -p 643 <host>" shows whether it is reachable.

05 Related
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