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Port 5911 (ats-acars, cpdlc)

IANA assigns port 5911 to ats-acars, cpdlc: Air Traffic Services applications using ACARS.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
ats-acars TCP Air Traffic Services applications using ACARS Eivan Cerasi -
ats-acars UDP Air Traffic Services applications using ACARS Eivan Cerasi -
cpdlc SCTP Controller Pilot Data Link Communication Justin Yu -

Registry dates for this port: registered 2008-10-10, last modified 2022-08-08.

Check what is listening on port 5911

Linux: is anything listening on TCP 5911?
sudo ss -tlnp 'sport = :5911'
Linux: UDP 5911
sudo ss -ulnp 'sport = :5911'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5911
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5911 '
Windows (Command Prompt)
netstat -ano | findstr :5911
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5911 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5911
From Windows
Test-NetConnection HOST -Port 5911
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 5911

Block port 5911 in the firewall

ufw
sudo ufw deny 5911/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5911 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5911 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5911' -Direction Inbound -Protocol TCP -LocalPort 5911 -Action Block
ufw
sudo ufw deny 5911/udp
iptables
sudo iptables -A INPUT -p udp --dport 5911 -j DROP
nftables
sudo nft add rule inet filter input udp dport 5911 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 5911' -Direction Inbound -Protocol UDP -LocalPort 5911 -Action Block

Related ports

5909agma5910ats-atn, cm5912ais-met, fis5913aoc-acars, ads-c

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