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// Other services

Port 637: lanserver

Port 637 is assigned by IANA to lanserver (lanserver).

637

How lanserver works

Other services
client:637lanserverresponse client:637lanserverresponse

The client sends a request to port 637 and the lanserver 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 637 dangerous?

We have no specific security note for port 637. 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 637

ServicePortTransportDescriptionReferenceUpdated
lanserver 637 TCP, UDP lanserver - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 637, and is it reachable?

Linux

sudo ss -ltnup 'sport = :637'      # process listening on 637
sudo lsof -nP -i :637

macOS

sudo lsof -nP -i :637

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 637 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 637
netstat -ano | findstr :637

From another machine

nmap -p 637 -sV <host>
sudo nmap -sU -p 637 <host>
nc -zv <host> 637

Block it in the firewall

sudo ufw deny 637/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 637" -Direction Inbound -LocalPort 637 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 637 used for?

Port 637 is assigned by IANA to lanserver (lanserver).

Is port 637 TCP or UDP?

Port 637 is registered for TCP and UDP.

Is it safe to open port 637?

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 637 is open?

On Linux run "ss -ltnup 'sport = :637'", on macOS "lsof -nP -i :637", and on Windows "netstat -ano | findstr :637" to see the local process. From another machine, "nmap -p 637 <host>" shows whether it is reachable.

05 Related
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