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// Network services

Port 9903: Multicast Ping Protocol

Port 9903 is assigned by IANA to multicast-ping (Multicast Ping Protocol).

9903

How multicast-ping works

Network services
client:9903multicast-pingresponse client:9903multicast-pingresponse

The client sends a request to port 9903 and the multicast-ping service answers.

Transport
UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Network services
01 Security

Is port 9903 dangerous?

We have no specific security note for port 9903. 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 9903

ServicePortTransportDescriptionReferenceUpdated
multicast-ping 9903 UDP Multicast Ping Protocol RFC 6450 2011-12-09
-9903-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 9903, and is it reachable?

Linux

sudo ss -ltnup 'sport = :9903'      # process listening on 9903
sudo lsof -nP -i :9903

macOS

sudo lsof -nP -i :9903

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9903 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 9903
netstat -ano | findstr :9903

From another machine

nmap -p 9903 -sV <host>
sudo nmap -sU -p 9903 <host>
nc -zv <host> 9903

Block it in the firewall

sudo ufw deny 9903/udp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 9903" -Direction Inbound -LocalPort 9903 -Protocol UDP -Action Block  # Windows
04 FAQ
What is port 9903 used for?

Port 9903 is assigned by IANA to multicast-ping (Multicast Ping Protocol).

Is port 9903 TCP or UDP?

Port 9903 is registered for UDP.

Is it safe to open port 9903?

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 9903 is open?

On Linux run "ss -ltnup 'sport = :9903'", on macOS "lsof -nP -i :9903", and on Windows "netstat -ano | findstr :9903" to see the local process. From another machine, "nmap -p 9903 <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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