HTTPfy

Port 6688 (clever-tcpip)

IANA assigns port 6688 to clever-tcpip: CleverView for TCP/IP Message Service.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference
clever-tcpip TCP CleverView for TCP/IP Message Service David Cheng -

Registry dates for this port: registered 2009-10-13.

Check what is listening on port 6688

Linux: is anything listening on TCP 6688?
sudo ss -tlnp 'sport = :6688'
Linux / macOS: which process owns the port
sudo lsof -nP -i :6688
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':6688 '
Windows (Command Prompt)
netstat -ano | findstr :6688
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 6688 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 6688
From Windows
Test-NetConnection HOST -Port 6688

Block port 6688 in the firewall

ufw
sudo ufw deny 6688/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 6688 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 6688 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 6688' -Direction Inbound -Protocol TCP -LocalPort 6688 -Action Block

Related ports

6679osaut6687clever-ctrace6689tsa6690cleverdetect

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