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Port 3616 (cd3o-protocol)

IANA assigns port 3616 to cd3o-protocol: cd3o Control Protocol.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
cd3o-protocol TCP cd3o Control Protocol Chris Wilcox -
cd3o-protocol UDP cd3o Control Protocol Chris Wilcox -

Registry dates for this port: registered 2002-10.

Check what is listening on port 3616

Linux: is anything listening on TCP 3616?
sudo ss -tlnp 'sport = :3616'
Linux: UDP 3616
sudo ss -ulnp 'sport = :3616'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3616
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3616 '
Windows (Command Prompt)
netstat -ano | findstr :3616
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3616 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3616
From Windows
Test-NetConnection HOST -Port 3616
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3616

Block port 3616 in the firewall

ufw
sudo ufw deny 3616/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3616 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3616 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3616' -Direction Inbound -Protocol TCP -LocalPort 3616 -Action Block
ufw
sudo ufw deny 3616/udp
iptables
sudo iptables -A INPUT -p udp --dport 3616 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3616 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3616' -Direction Inbound -Protocol UDP -LocalPort 3616 -Action Block

Related ports

3614sigma-port3615start-network3617sharp-server3618aairnet-1

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