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Port 1131 (caspssl)

IANA assigns port 1131 to caspssl: CAC App Service Protocol Encripted.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
caspssl TCP CAC App Service Protocol Encripted Enrique Corujo -
caspssl UDP CAC App Service Protocol Encripted Enrique Corujo -

Registry dates for this port: registered 2006-02.

Check what is listening on port 1131

Linux: is anything listening on TCP 1131?
sudo ss -tlnp 'sport = :1131'
Linux: UDP 1131
sudo ss -ulnp 'sport = :1131'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1131
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1131 '
Windows (Command Prompt)
netstat -ano | findstr :1131
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1131 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1131
From Windows
Test-NetConnection HOST -Port 1131
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1131

Block port 1131 in the firewall

ufw
sudo ufw deny 1131/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1131 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1131 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1131' -Direction Inbound -Protocol TCP -LocalPort 1131 -Action Block
ufw
sudo ufw deny 1131/udp
iptables
sudo iptables -A INPUT -p udp --dport 1131 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1131 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1131' -Direction Inbound -Protocol UDP -LocalPort 1131 -Action Block

Related ports

1129saphostctrls1130casp1132kvm-via-ip1133dfn

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