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Port 633 (servstat)

IANA assigns port 633 to servstat: Service Status update (Sterling Software).

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
servstat TCP Service Status update (Sterling Software) Greg Rose -
servstat UDP Service Status update (Sterling Software) Greg Rose -

Check what is listening on port 633

Linux: is anything listening on TCP 633?
sudo ss -tlnp 'sport = :633'
Linux: UDP 633
sudo ss -ulnp 'sport = :633'
Linux / macOS: which process owns the port
sudo lsof -nP -i :633
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':633 '
Windows (Command Prompt)
netstat -ano | findstr :633
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 633 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 633
From Windows
Test-NetConnection HOST -Port 633
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 633

Block port 633 in the firewall

ufw
sudo ufw deny 633/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 633 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 633 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 633' -Direction Inbound -Protocol TCP -LocalPort 633 -Action Block
ufw
sudo ufw deny 633/udp
iptables
sudo iptables -A INPUT -p udp --dport 633 -j DROP
nftables
sudo nft add rule inet filter input udp dport 633 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 633' -Direction Inbound -Protocol UDP -LocalPort 633 -Action Block

Related ports

631IPP / CUPS632bmpp634ginad635rlzdbase

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