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Port 473 (hybrid-pop)

IANA assigns port 473 to hybrid-pop.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
hybrid-pop TCP hybrid-pop Rami Rubin -
hybrid-pop UDP hybrid-pop Rami Rubin -

Check what is listening on port 473

Linux: is anything listening on TCP 473?
sudo ss -tlnp 'sport = :473'
Linux: UDP 473
sudo ss -ulnp 'sport = :473'
Linux / macOS: which process owns the port
sudo lsof -nP -i :473
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':473 '
Windows (Command Prompt)
netstat -ano | findstr :473
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 473 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 473
From Windows
Test-NetConnection HOST -Port 473
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 473

Block port 473 in the firewall

ufw
sudo ufw deny 473/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 473 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 473 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 473' -Direction Inbound -Protocol TCP -LocalPort 473 -Action Block
ufw
sudo ufw deny 473/udp
iptables
sudo iptables -A INPUT -p udp --dport 473 -j DROP
nftables
sudo nft add rule inet filter input udp dport 473 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 473' -Direction Inbound -Protocol UDP -LocalPort 473 -Action Block

Related ports

471mondex472ljk-login474tn-tl-w1, tn-tl-w2475tcpnethaspsrv

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