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Port 5503 (fcp-srvr-inst2)

IANA assigns port 5503 to fcp-srvr-inst2.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
fcp-srvr-inst2 TCP fcp-srvr-inst2 Ken Wittmer -
fcp-srvr-inst2 UDP fcp-srvr-inst2 Ken Wittmer -

Check what is listening on port 5503

Linux: is anything listening on TCP 5503?
sudo ss -tlnp 'sport = :5503'
Linux: UDP 5503
sudo ss -ulnp 'sport = :5503'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5503
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5503 '
Windows (Command Prompt)
netstat -ano | findstr :5503
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5503 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5503
From Windows
Test-NetConnection HOST -Port 5503
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 5503

Block port 5503 in the firewall

ufw
sudo ufw deny 5503/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5503 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5503 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5503' -Direction Inbound -Protocol TCP -LocalPort 5503 -Action Block
ufw
sudo ufw deny 5503/udp
iptables
sudo iptables -A INPUT -p udp --dport 5503 -j DROP
nftables
sudo nft add rule inet filter input udp dport 5503 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 5503' -Direction Inbound -Protocol UDP -LocalPort 5503 -Action Block

Related ports

5501fcp-addr-srvr25502fcp-srvr-inst15504fcp-cics-gw15505checkoutdb

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