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// Other services

Port 2103: Zephyr serv-hm connection

Port 2103 is assigned by IANA to zephyr-clt (Zephyr serv-hm connection).

2103

How zephyr-clt works

Other services
client:2103zephyr-cltresponse client:2103zephyr-cltresponse

The client sends a request to port 2103 and the zephyr-clt 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 2103 dangerous?

We have no specific security note for port 2103. 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 2103

ServicePortTransportDescriptionReferenceUpdated
zephyr-clt 2103 TCP, UDP Zephyr serv-hm connection - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 2103, and is it reachable?

Linux

sudo ss -ltnup 'sport = :2103'      # process listening on 2103
sudo lsof -nP -i :2103

macOS

sudo lsof -nP -i :2103

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 2103 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 2103
netstat -ano | findstr :2103

From another machine

nmap -p 2103 -sV <host>
sudo nmap -sU -p 2103 <host>
nc -zv <host> 2103

Block it in the firewall

sudo ufw deny 2103/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 2103" -Direction Inbound -LocalPort 2103 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 2103 used for?

Port 2103 is assigned by IANA to zephyr-clt (Zephyr serv-hm connection).

Is port 2103 TCP or UDP?

Port 2103 is registered for TCP and UDP.

Is it safe to open port 2103?

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 2103 is open?

On Linux run "ss -ltnup 'sport = :2103'", on macOS "lsof -nP -i :2103", and on Windows "netstat -ano | findstr :2103" to see the local process. From another machine, "nmap -p 2103 <host>" shows whether it is reachable.

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