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// File transfer & sharing

Port 911: xact-backup

Port 911 is assigned by IANA to xact-backup (xact-backup).

911

How xact-backup works

File transfer & sharing
client:9111/32/33/3xact-backup client:9111/32/33/3xact-backup

Files are sent over port 911 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
Assigned1 registered service
Range
Well-known (0-1023)
Category
File transfer & sharing
01 Security

Is port 911 dangerous?

We have no specific security note for port 911. 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 911

ServicePortTransportDescriptionReferenceUpdated
xact-backup 911 TCP, UDP xact-backup - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 911, and is it reachable?

Linux

sudo ss -ltnup 'sport = :911'      # process listening on 911
sudo lsof -nP -i :911

macOS

sudo lsof -nP -i :911

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 911 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 911
netstat -ano | findstr :911

From another machine

nmap -p 911 -sV <host>
sudo nmap -sU -p 911 <host>
nc -zv <host> 911

Block it in the firewall

sudo ufw deny 911/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 911" -Direction Inbound -LocalPort 911 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 911 used for?

Port 911 is assigned by IANA to xact-backup (xact-backup).

Is port 911 TCP or UDP?

Port 911 is registered for TCP and UDP.

Is it safe to open port 911?

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 911 is open?

On Linux run "ss -ltnup 'sport = :911'", on macOS "lsof -nP -i :911", and on Windows "netstat -ano | findstr :911" to see the local process. From another machine, "nmap -p 911 <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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