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Port 1646 (sa-msg-port)

IANA assigns port 1646 to sa-msg-port.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
sa-msg-port TCP sa-msg-port Eric Whitehill -
sa-msg-port UDP sa-msg-port Eric Whitehill -

Check what is listening on port 1646

Linux: is anything listening on TCP 1646?
sudo ss -tlnp 'sport = :1646'
Linux: UDP 1646
sudo ss -ulnp 'sport = :1646'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1646
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1646 '
Windows (Command Prompt)
netstat -ano | findstr :1646
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1646 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1646
From Windows
Test-NetConnection HOST -Port 1646
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1646

Block port 1646 in the firewall

ufw
sudo ufw deny 1646/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1646 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1646 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1646' -Direction Inbound -Protocol TCP -LocalPort 1646 -Action Block
ufw
sudo ufw deny 1646/udp
iptables
sudo iptables -A INPUT -p udp --dport 1646 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1646 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1646' -Direction Inbound -Protocol UDP -LocalPort 1646 -Action Block

Related ports

1644saiseh1645sightline1647rsap1648concurrent-lm

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