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// Network services

Port 530: rpc

Port 530 is assigned by IANA to courier (rpc).

530

How courier works

Network services
client:530courierresponse client:530courierresponse

The client sends a request to port 530 and the courier service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
Network services
01 Security

Is port 530 dangerous?

We have no specific security note for port 530. Its risk depends on the program actually listening on it. General advice for network services services:

  • Answer only the networks that need the service (no open resolvers, relays or reflectors).
  • UDP services can be abused for DDoS amplification: rate-limit or block them at the edge.
  • Disable legacy test services that have no use in production.
02 Registry

IANA registry entries for port 530

ServicePortTransportDescriptionReferenceUpdated
courier 530 TCP, UDP rpc - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 530, and is it reachable?

Linux

sudo ss -ltnup 'sport = :530'      # process listening on 530
sudo lsof -nP -i :530

macOS

sudo lsof -nP -i :530

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 530 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 530
netstat -ano | findstr :530

From another machine

nmap -p 530 -sV <host>
sudo nmap -sU -p 530 <host>
nc -zv <host> 530

Block it in the firewall

sudo ufw deny 530/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 530" -Direction Inbound -LocalPort 530 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 530 used for?

Port 530 is assigned by IANA to courier (rpc).

Is port 530 TCP or UDP?

Port 530 is registered for TCP and UDP.

Is it safe to open port 530?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Answer only the networks that need the service (no open resolvers, relays or reflectors).

How do I check if port 530 is open?

On Linux run "ss -ltnup 'sport = :530'", on macOS "lsof -nP -i :530", and on Windows "netstat -ano | findstr :530" to see the local process. From another machine, "nmap -p 530 <host>" shows whether it is reachable.

05 Related
:53 DNS tcp · udp · moderate risk :135 MS RPC tcp · udp · high risk :123 NTP udp · tcp · moderate risk :67 DHCP server udp · tcp · moderate risk :111 rpcbind tcp · udp · high risk :9100 Raw printing (JetDirect) tcp · udp · high risk :631 IPP / CUPS tcp · udp · high risk :5353 mDNS udp · tcp · moderate risk

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