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Port 165 (xns-courier)

IANA assigns port 165 to xns-courier: Xerox.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
xns-courier TCP Xerox Susie Armstrong 2 -
xns-courier UDP Xerox Susie Armstrong 2 -

Check what is listening on port 165

Linux: is anything listening on TCP 165?
sudo ss -tlnp 'sport = :165'
Linux: UDP 165
sudo ss -ulnp 'sport = :165'
Linux / macOS: which process owns the port
sudo lsof -nP -i :165
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':165 '
Windows (Command Prompt)
netstat -ano | findstr :165
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 165 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 165
From Windows
Test-NetConnection HOST -Port 165
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 165

Block port 165 in the firewall

ufw
sudo ufw deny 165/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 165 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 165 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 165' -Direction Inbound -Protocol TCP -LocalPort 165 -Action Block
ufw
sudo ufw deny 165/udp
iptables
sudo iptables -A INPUT -p udp --dport 165 -j DROP
nftables
sudo nft add rule inet filter input udp dport 165 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 165' -Direction Inbound -Protocol UDP -LocalPort 165 -Action Block

Related ports

163cmip-man164cmip-agent166s-net167namp

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