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Port 5904 (ag-swim)

IANA assigns port 5904 to ag-swim: Air-Ground SWIM.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
ag-swim TCP Air-Ground SWIM
Defined TXT keys: AG-SWIM International Civil Aviation Organisation -
ag-swim UDP Air-Ground SWIM
Defined TXT keys: AG-SWIM International Civil Aviation Organisation -
ag-swim SCTP Air-Ground SWIM
Defined TXT keys: AG-SWIM International Civil Aviation Organisation -

Registry dates for this port: registered 2022-06-03.

Check what is listening on port 5904

Linux: is anything listening on TCP 5904?
sudo ss -tlnp 'sport = :5904'
Linux: UDP 5904
sudo ss -ulnp 'sport = :5904'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5904
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5904 '
Windows (Command Prompt)
netstat -ano | findstr :5904
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5904 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5904
From Windows
Test-NetConnection HOST -Port 5904
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 5904

Block port 5904 in the firewall

ufw
sudo ufw deny 5904/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5904 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5904 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5904' -Direction Inbound -Protocol TCP -LocalPort 5904 -Action Block
ufw
sudo ufw deny 5904/udp
iptables
sudo iptables -A INPUT -p udp --dport 5904 -j DROP
nftables
sudo nft add rule inet filter input udp dport 5904 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 5904' -Direction Inbound -Protocol UDP -LocalPort 5904 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.