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// Other services

Port 10103: eZrelay

Port 10103 is assigned by IANA to ezrelay (eZrelay).

10103

How ezrelay works

Other services
client:10103ezrelayresponse client:10103ezrelayresponse

The client sends a request to port 10103 and the ezrelay 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
Registered (1024-49151)
Category
Other services
01 Security

Is port 10103 dangerous?

We have no specific security note for port 10103. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 10103

ServicePortTransportDescriptionReferenceUpdated
ezrelay 10103 TCP, UDP eZrelay - 2002-03

// source: IANA service name and port number registry

03 Check it

Which program uses port 10103, and is it reachable?

Linux

sudo ss -ltnup 'sport = :10103'      # process listening on 10103
sudo lsof -nP -i :10103

macOS

sudo lsof -nP -i :10103

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 10103 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 10103
netstat -ano | findstr :10103

From another machine

nmap -p 10103 -sV <host>
sudo nmap -sU -p 10103 <host>
nc -zv <host> 10103

Block it in the firewall

sudo ufw deny 10103/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 10103" -Direction Inbound -LocalPort 10103 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 10103 used for?

Port 10103 is assigned by IANA to ezrelay (eZrelay).

Is port 10103 TCP or UDP?

Port 10103 is registered for TCP and UDP.

Is it safe to open port 10103?

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. Close the port if nothing on the host needs it.

How do I check if port 10103 is open?

On Linux run "ss -ltnup 'sport = :10103'", on macOS "lsof -nP -i :10103", and on Windows "netstat -ano | findstr :10103" to see the local process. From another machine, "nmap -p 10103 <host>" shows whether it is reachable.

05 Related
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