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Port 35 (any private printer server)

IANA assigns port 35 to any private printer server.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
- TCP any private printer server Jon Postel -
- UDP any private printer server Jon Postel -

Check what is listening on port 35

Linux: is anything listening on TCP 35?
sudo ss -tlnp 'sport = :35'
Linux: UDP 35
sudo ss -ulnp 'sport = :35'
Linux / macOS: which process owns the port
sudo lsof -nP -i :35
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':35 '
Windows (Command Prompt)
netstat -ano | findstr :35
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 35 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 35
From Windows
Test-NetConnection HOST -Port 35
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 35

Block port 35 in the firewall

ufw
sudo ufw deny 35/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 35 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 35 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 35' -Direction Inbound -Protocol TCP -LocalPort 35 -Action Block
ufw
sudo ufw deny 35/udp
iptables
sudo iptables -A INPUT -p udp --dport 35 -j DROP
nftables
sudo nft add rule inet filter input udp dport 35 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 35' -Direction Inbound -Protocol UDP -LocalPort 35 -Action Block

Related ports

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