HTTPfy

Port 530 (courier)

IANA assigns port 530 to courier: rpc.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
courier TCP rpc - -
courier UDP rpc - -

Check what is listening on port 530

Linux: is anything listening on TCP 530?
sudo ss -tlnp 'sport = :530'
Linux: UDP 530
sudo ss -ulnp 'sport = :530'
Linux / macOS: which process owns the port
sudo lsof -nP -i :530
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':530 '
Windows (Command Prompt)
netstat -ano | findstr :530
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 530 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 530
From Windows
Test-NetConnection HOST -Port 530
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 530

Block port 530 in the firewall

ufw
sudo ufw deny 530/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 530 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 530 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 530' -Direction Inbound -Protocol TCP -LocalPort 530 -Action Block
ufw
sudo ufw deny 530/udp
iptables
sudo iptables -A INPUT -p udp --dport 530 -j DROP
nftables
sudo nft add rule inet filter input udp dport 530 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 530' -Direction Inbound -Protocol UDP -LocalPort 530 -Action Block

Related ports

528custix529irc-serv531conference532netnews

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