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Port 901 (smpnameres)

IANA assigns port 901 to smpnameres: SMPNAMERES.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
smpnameres TCP SMPNAMERES Leif Ekblad -
smpnameres UDP SMPNAMERES Leif Ekblad -

Check what is listening on port 901

Linux: is anything listening on TCP 901?
sudo ss -tlnp 'sport = :901'
Linux: UDP 901
sudo ss -ulnp 'sport = :901'
Linux / macOS: which process owns the port
sudo lsof -nP -i :901
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':901 '
Windows (Command Prompt)
netstat -ano | findstr :901
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 901 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 901
From Windows
Test-NetConnection HOST -Port 901
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 901

Block port 901 in the firewall

ufw
sudo ufw deny 901/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 901 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 901 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 901' -Direction Inbound -Protocol TCP -LocalPort 901 -Action Block
ufw
sudo ufw deny 901/udp
iptables
sudo iptables -A INPUT -p udp --dport 901 -j DROP
nftables
sudo nft add rule inet filter input udp dport 901 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 901' -Direction Inbound -Protocol UDP -LocalPort 901 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.