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// Other services

Port 21845: webphone

Port 21845 is assigned by IANA to webphone (webphone).

21845

How webphone works

Other services
client:21845webphoneresponse client:21845webphoneresponse

The client sends a request to port 21845 and the webphone 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 21845 dangerous?

We have no specific security note for port 21845. 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 21845

ServicePortTransportDescriptionReferenceUpdated
webphone 21845 TCP, UDP webphone - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 21845, and is it reachable?

Linux

sudo ss -ltnup 'sport = :21845'      # process listening on 21845
sudo lsof -nP -i :21845

macOS

sudo lsof -nP -i :21845

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 21845 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 21845
netstat -ano | findstr :21845

From another machine

nmap -p 21845 -sV <host>
sudo nmap -sU -p 21845 <host>
nc -zv <host> 21845

Block it in the firewall

sudo ufw deny 21845/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 21845" -Direction Inbound -LocalPort 21845 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 21845 used for?

Port 21845 is assigned by IANA to webphone (webphone).

Is port 21845 TCP or UDP?

Port 21845 is registered for TCP and UDP.

Is it safe to open port 21845?

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 21845 is open?

On Linux run "ss -ltnup 'sport = :21845'", on macOS "lsof -nP -i :21845", and on Windows "netstat -ano | findstr :21845" to see the local process. From another machine, "nmap -p 21845 <host>" shows whether it is reachable.

05 Related
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