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// Other services

Port 3850: QTMS Bootstrap Protocol

Port 3850 is assigned by IANA to qtms-bootstrap (QTMS Bootstrap Protocol).

3850

How qtms-bootstrap works

Other services
client:3850qtms-bootstrapresponse client:3850qtms-bootstrapresponse

The client sends a request to port 3850 and the qtms-bootstrap 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 3850 dangerous?

We have no specific security note for port 3850. 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 3850

ServicePortTransportDescriptionReferenceUpdated
qtms-bootstrap 3850 TCP, UDP QTMS Bootstrap Protocol - 2003-08

// source: IANA service name and port number registry

03 Check it

Which program uses port 3850, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3850'      # process listening on 3850
sudo lsof -nP -i :3850

macOS

sudo lsof -nP -i :3850

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3850 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3850
netstat -ano | findstr :3850

From another machine

nmap -p 3850 -sV <host>
sudo nmap -sU -p 3850 <host>
nc -zv <host> 3850

Block it in the firewall

sudo ufw deny 3850/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3850" -Direction Inbound -LocalPort 3850 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3850 used for?

Port 3850 is assigned by IANA to qtms-bootstrap (QTMS Bootstrap Protocol).

Is port 3850 TCP or UDP?

Port 3850 is registered for TCP and UDP.

Is it safe to open port 3850?

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 3850 is open?

On Linux run "ss -ltnup 'sport = :3850'", on macOS "lsof -nP -i :3850", and on Windows "netstat -ano | findstr :3850" to see the local process. From another machine, "nmap -p 3850 <host>" shows whether it is reachable.

05 Related
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