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Port 439 (dasp)

IANA assigns port 439 to dasp.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
dasp TCP dasp Thomas Obermair -
dasp UDP dasp Thomas Obermair -

Check what is listening on port 439

Linux: is anything listening on TCP 439?
sudo ss -tlnp 'sport = :439'
Linux: UDP 439
sudo ss -ulnp 'sport = :439'
Linux / macOS: which process owns the port
sudo lsof -nP -i :439
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':439 '
Windows (Command Prompt)
netstat -ano | findstr :439
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 439 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 439
From Windows
Test-NetConnection HOST -Port 439
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 439

Block port 439 in the firewall

ufw
sudo ufw deny 439/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 439 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 439 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 439' -Direction Inbound -Protocol TCP -LocalPort 439 -Action Block
ufw
sudo ufw deny 439/udp
iptables
sudo iptables -A INPUT -p udp --dport 439 -j DROP
nftables
sudo nft add rule inet filter input udp dport 439 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 439' -Direction Inbound -Protocol UDP -LocalPort 439 -Action Block

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437comscm438dsfgw440sgcp441decvms-sysmgt

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