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Port 5603 (a1-bs)

IANA assigns port 5603 to a1-bs: A1-BS.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
a1-bs TCP A1-BS Mike Dolan -
a1-bs UDP A1-BS Mike Dolan -

Check what is listening on port 5603

Linux: is anything listening on TCP 5603?
sudo ss -tlnp 'sport = :5603'
Linux: UDP 5603
sudo ss -ulnp 'sport = :5603'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5603
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5603 '
Windows (Command Prompt)
netstat -ano | findstr :5603
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5603 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5603
From Windows
Test-NetConnection HOST -Port 5603
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 5603

Block port 5603 in the firewall

ufw
sudo ufw deny 5603/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5603 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5603 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5603' -Direction Inbound -Protocol TCP -LocalPort 5603 -Action Block
ufw
sudo ufw deny 5603/udp
iptables
sudo iptables -A INPUT -p udp --dport 5603 -j DROP
nftables
sudo nft add rule inet filter input udp dport 5603 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 5603' -Direction Inbound -Protocol UDP -LocalPort 5603 -Action Block

Related ports

5601Kibana5602a1-msc5604a3-sdunode5605a4-sdunode

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