Port 5903 (ff-ice)

IANA assigns port 5903 to ff-ice: Flight & Flow Info for Collaborative Env.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference

ff-ice TCP Flight & Flow Info for Collaborative Env
Defined TXT keys: FF-ICE International Civil Aviation Organisation -

ff-ice UDP Flight & Flow Info for Collaborative Env
Defined TXT keys: FF-ICE International Civil Aviation Organisation -

ff-ice SCTP Flight & Flow Info for Collaborative Env
Defined TXT keys: FF-ICE International Civil Aviation Organisation -

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

Linux: is anything listening on TCP 5903?

sudo ss -tlnp 'sport = :5903'

Linux: UDP 5903

sudo ss -ulnp 'sport = :5903'

Linux / macOS: which process owns the port

sudo lsof -nP -i :5903

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':5903 '

Windows (Command Prompt)

netstat -ano | findstr :5903

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5903 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 5903

From Windows

Test-NetConnection HOST -Port 5903

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 5903

ufw

sudo ufw deny 5903/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 5903 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 5903 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 5903' -Direction Inbound -Protocol TCP -LocalPort 5903 -Action Block

ufw

sudo ufw deny 5903/udp

iptables

sudo iptables -A INPUT -p udp --dport 5903 -j DROP

nftables

sudo nft add rule inet filter input udp dport 5903 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 5903' -Direction Inbound -Protocol UDP -LocalPort 5903 -Action Block

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