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Port 3056 (cdl-server)

IANA assigns port 3056 to cdl-server: CDL Server.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
cdl-server TCP CDL Server Paul Roberts -
cdl-server UDP CDL Server Paul Roberts -

Check what is listening on port 3056

Linux: is anything listening on TCP 3056?
sudo ss -tlnp 'sport = :3056'
Linux: UDP 3056
sudo ss -ulnp 'sport = :3056'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3056
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3056 '
Windows (Command Prompt)
netstat -ano | findstr :3056
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3056 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3056
From Windows
Test-NetConnection HOST -Port 3056
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3056

Block port 3056 in the firewall

ufw
sudo ufw deny 3056/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3056 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3056 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3056' -Direction Inbound -Protocol TCP -LocalPort 3056 -Action Block
ufw
sudo ufw deny 3056/udp
iptables
sudo iptables -A INPUT -p udp --dport 3056 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3056 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3056' -Direction Inbound -Protocol UDP -LocalPort 3056 -Action Block

Related ports

3054amt-cnf-prot3055policyserver3057goahead-fldup3058videobeans

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