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// Other services

Port 3723: Sychron Service Daemon

Port 3723 is assigned by IANA to sychrond (Sychron Service Daemon).

3723

How sychrond works

Other services
client:3723sychrondresponse client:3723sychrondresponse

The client sends a request to port 3723 and the sychrond 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 3723 dangerous?

We have no specific security note for port 3723. 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 3723

ServicePortTransportDescriptionReferenceUpdated
sychrond 3723 TCP, UDP Sychron Service Daemon - 2003-03

// source: IANA service name and port number registry

03 Check it

Which program uses port 3723, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3723'      # process listening on 3723
sudo lsof -nP -i :3723

macOS

sudo lsof -nP -i :3723

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3723 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3723
netstat -ano | findstr :3723

From another machine

nmap -p 3723 -sV <host>
sudo nmap -sU -p 3723 <host>
nc -zv <host> 3723

Block it in the firewall

sudo ufw deny 3723/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3723" -Direction Inbound -LocalPort 3723 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3723 used for?

Port 3723 is assigned by IANA to sychrond (Sychron Service Daemon).

Is port 3723 TCP or UDP?

Port 3723 is registered for TCP and UDP.

Is it safe to open port 3723?

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 3723 is open?

On Linux run "ss -ltnup 'sport = :3723'", on macOS "lsof -nP -i :3723", and on Windows "netstat -ano | findstr :3723" to see the local process. From another machine, "nmap -p 3723 <host>" shows whether it is reachable.

05 Related
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