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// Network services

Port 3849: SPACEWAY DNS Preload

Port 3849 is assigned by IANA to spw-dnspreload (SPACEWAY DNS Preload).

3849

How spw-dnspreload works

Network services
client:3849spw-dnspreloadresponse client:3849spw-dnspreloadresponse

The client sends a request to port 3849 and the spw-dnspreload 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
Network services
01 Security

Is port 3849 dangerous?

We have no specific security note for port 3849. Its risk depends on the program actually listening on it. General advice for network services services:

  • Answer only the networks that need the service (no open resolvers, relays or reflectors).
  • UDP services can be abused for DDoS amplification: rate-limit or block them at the edge.
  • Disable legacy test services that have no use in production.
02 Registry

IANA registry entries for port 3849

ServicePortTransportDescriptionReferenceUpdated
spw-dnspreload 3849 TCP, UDP SPACEWAY DNS Preload - 2003-08

// source: IANA service name and port number registry

03 Check it

Which program uses port 3849, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3849'      # process listening on 3849
sudo lsof -nP -i :3849

macOS

sudo lsof -nP -i :3849

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3849 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3849
netstat -ano | findstr :3849

From another machine

nmap -p 3849 -sV <host>
sudo nmap -sU -p 3849 <host>
nc -zv <host> 3849

Block it in the firewall

sudo ufw deny 3849/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3849" -Direction Inbound -LocalPort 3849 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3849 used for?

Port 3849 is assigned by IANA to spw-dnspreload (SPACEWAY DNS Preload).

Is port 3849 TCP or UDP?

Port 3849 is registered for TCP and UDP.

Is it safe to open port 3849?

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. Answer only the networks that need the service (no open resolvers, relays or reflectors).

How do I check if port 3849 is open?

On Linux run "ss -ltnup 'sport = :3849'", on macOS "lsof -nP -i :3849", and on Windows "netstat -ano | findstr :3849" to see the local process. From another machine, "nmap -p 3849 <host>" shows whether it is reachable.

05 Related
:53 DNS tcp · udp · moderate risk :135 MS RPC tcp · udp · high risk :123 NTP udp · tcp · moderate risk :67 DHCP server udp · tcp · moderate risk :111 rpcbind tcp · udp · high risk :9100 Raw printing (JetDirect) tcp · udp · high risk :631 IPP / CUPS tcp · udp · high risk :5353 mDNS udp · tcp · moderate risk

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