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Port 535 (iiop)

IANA assigns port 535 to iiop.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
iiop TCP iiop Jeff M Michaud -
iiop UDP iiop Jeff M Michaud -

Check what is listening on port 535

Linux: is anything listening on TCP 535?
sudo ss -tlnp 'sport = :535'
Linux: UDP 535
sudo ss -ulnp 'sport = :535'
Linux / macOS: which process owns the port
sudo lsof -nP -i :535
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':535 '
Windows (Command Prompt)
netstat -ano | findstr :535
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 535 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 535
From Windows
Test-NetConnection HOST -Port 535
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 535

Block port 535 in the firewall

ufw
sudo ufw deny 535/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 535 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 535 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 535' -Direction Inbound -Protocol TCP -LocalPort 535 -Action Block
ufw
sudo ufw deny 535/udp
iptables
sudo iptables -A INPUT -p udp --dport 535 -j DROP
nftables
sudo nft add rule inet filter input udp dport 535 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 535' -Direction Inbound -Protocol UDP -LocalPort 535 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.