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Port 1645 (sightline)

IANA assigns port 1645 to sightline: SightLine.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
sightline TCP SightLine admin -
sightline UDP SightLine admin -

Check what is listening on port 1645

Linux: is anything listening on TCP 1645?
sudo ss -tlnp 'sport = :1645'
Linux: UDP 1645
sudo ss -ulnp 'sport = :1645'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1645
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1645 '
Windows (Command Prompt)
netstat -ano | findstr :1645
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1645 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1645
From Windows
Test-NetConnection HOST -Port 1645
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1645

Block port 1645 in the firewall

ufw
sudo ufw deny 1645/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1645 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1645 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1645' -Direction Inbound -Protocol TCP -LocalPort 1645 -Action Block
ufw
sudo ufw deny 1645/udp
iptables
sudo iptables -A INPUT -p udp --dport 1645 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1645 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1645' -Direction Inbound -Protocol UDP -LocalPort 1645 -Action Block

Related ports

1643isis-ambc1644saiseh1646sa-msg-port1647rsap

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