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Port 911 (xact-backup)

IANA assigns port 911 to xact-backup.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
xact-backup TCP xact-backup Bill Carroll -
xact-backup UDP xact-backup Bill Carroll -

Check what is listening on port 911

Linux: is anything listening on TCP 911?
sudo ss -tlnp 'sport = :911'
Linux: UDP 911
sudo ss -ulnp 'sport = :911'
Linux / macOS: which process owns the port
sudo lsof -nP -i :911
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':911 '
Windows (Command Prompt)
netstat -ano | findstr :911
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 911 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 911
From Windows
Test-NetConnection HOST -Port 911
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 911

Block port 911 in the firewall

ufw
sudo ufw deny 911/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 911 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 911 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 911' -Direction Inbound -Protocol TCP -LocalPort 911 -Action Block
ufw
sudo ufw deny 911/udp
iptables
sudo iptables -A INPUT -p udp --dport 911 -j DROP
nftables
sudo nft add rule inet filter input udp dport 911 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 911' -Direction Inbound -Protocol UDP -LocalPort 911 -Action Block

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All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.