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// Other services

Port 644: dwr

Port 644 is assigned by IANA to dwr (dwr).

644

How dwr works

Other services
client:644dwrresponse client:644dwrresponse

The client sends a request to port 644 and the dwr 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 644 dangerous?

We have no specific security note for port 644. 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 644

ServicePortTransportDescriptionReferenceUpdated
dwr 644 TCP, UDP dwr - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 644, and is it reachable?

Linux

sudo ss -ltnup 'sport = :644'      # process listening on 644
sudo lsof -nP -i :644

macOS

sudo lsof -nP -i :644

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 644 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 644
netstat -ano | findstr :644

From another machine

nmap -p 644 -sV <host>
sudo nmap -sU -p 644 <host>
nc -zv <host> 644

Block it in the firewall

sudo ufw deny 644/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 644" -Direction Inbound -LocalPort 644 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 644 used for?

Port 644 is assigned by IANA to dwr (dwr).

Is port 644 TCP or UDP?

Port 644 is registered for TCP and UDP.

Is it safe to open port 644?

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 644 is open?

On Linux run "ss -ltnup 'sport = :644'", on macOS "lsof -nP -i :644", and on Windows "netstat -ano | findstr :644" to see the local process. From another machine, "nmap -p 644 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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