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// File transfer & sharing

Port 247: SUBNTBCST_TFTP

Port 247 is assigned by IANA to subntbcst_tftp (SUBNTBCST_TFTP), subntbcst-tftp (SUBNTBCST_TFTP IANA assigned this well-formed service name as a replacement for "subntbcst_tftp".).

247

How subntbcst_tftp works

File transfer & sharing
client:2471/32/33/3subntbcst_tftp client:2471/32/33/3subntbcst_tftp

Files are sent over port 247 in pieces and reassembled on the other side.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned2 registered services
Range
Well-known (0-1023)
Category
File transfer & sharing
01 Security

Is port 247 dangerous?

We have no specific security note for port 247. Its risk depends on the program actually listening on it. General advice for file transfer & sharing services:

  • Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).
  • Disable anonymous access and restrict shares or exports to known hosts.
  • Never publish file sharing protocols to the Internet.
02 Registry

IANA registry entries for port 247

ServicePortTransportDescriptionReferenceUpdated
subntbcst_tftp 247 TCP, UDP SUBNTBCST_TFTP - -
subntbcst-tftp 247 TCP, UDP SUBNTBCST_TFTP IANA assigned this well-formed service name as a replacement for "subntbcst_tftp". - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 247, and is it reachable?

Linux

sudo ss -ltnup 'sport = :247'      # process listening on 247
sudo lsof -nP -i :247

macOS

sudo lsof -nP -i :247

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 247 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 247
netstat -ano | findstr :247

From another machine

nmap -p 247 -sV <host>
sudo nmap -sU -p 247 <host>
nc -zv <host> 247

Block it in the firewall

sudo ufw deny 247/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 247" -Direction Inbound -LocalPort 247 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 247 used for?

Port 247 is assigned by IANA to subntbcst_tftp (SUBNTBCST_TFTP), subntbcst-tftp (SUBNTBCST_TFTP IANA assigned this well-formed service name as a replacement for "subntbcst_tftp".).

Is port 247 TCP or UDP?

Port 247 is registered for TCP and UDP.

Is it safe to open port 247?

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. Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).

How do I check if port 247 is open?

On Linux run "ss -ltnup 'sport = :247'", on macOS "lsof -nP -i :247", and on Windows "netstat -ano | findstr :247" to see the local process. From another machine, "nmap -p 247 <host>" shows whether it is reachable.

05 Related
:445 SMB tcp · udp · critical risk :21 FTP tcp · udp · sctp · high risk :139 NetBIOS Session tcp · udp · high risk :69 TFTP udp · tcp · high risk :2049 NFS tcp · udp · sctp · high risk :873 rsync tcp · udp · high risk :20 File Transfer [Default Data] tcp · udp · sctp :115 Simple File Transfer Protocol tcp · udp

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