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Port 644 (dwr)

IANA assigns port 644 to dwr.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
dwr TCP dwr Bill Fenner -
dwr UDP dwr Bill Fenner -

Check what is listening on port 644

Linux: is anything listening on TCP 644?
sudo ss -tlnp 'sport = :644'
Linux: UDP 644
sudo ss -ulnp 'sport = :644'
Linux / macOS: which process owns the port
sudo lsof -nP -i :644
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':644 '
Windows (Command Prompt)
netstat -ano | findstr :644
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 644 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 644
From Windows
Test-NetConnection HOST -Port 644
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 644

Block port 644 in the firewall

ufw
sudo ufw deny 644/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 644 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 644 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 644' -Direction Inbound -Protocol TCP -LocalPort 644 -Action Block
ufw
sudo ufw deny 644/udp
iptables
sudo iptables -A INPUT -p udp --dport 644 -j DROP
nftables
sudo nft add rule inet filter input udp dport 644 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 644' -Direction Inbound -Protocol UDP -LocalPort 644 -Action Block

Related ports

642esro-emsdp643sanity645pssc646LDP (MPLS)

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.