- Patch VPN gateways quickly: they are a top initial access target.
- Use certificates or MFA rather than shared secrets.
- Investigate unexpected tunnels and proxies: they are also attacker tools.
Port 16665: Reliable multipath data transport for high latencies
Port 16665 is assigned by IANA to axon-tunnel (Reliable multipath data transport for high latencies).
16665
How axon-tunnel works
VPN, tunnels & proxiesTraffic is wrapped in a tunnel between the two ends, so the network in between only sees the tunnel.
- Transport
- TCP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
- VPN, tunnels & proxies
Is port 16665 dangerous?
We have no specific security note for port 16665. Its risk depends on the program actually listening on it. General advice for vpn, tunnels & proxies services:
IANA registry entries for port 16665
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| axon-tunnel | 16665 | TCP | Reliable multipath data transport for high latencies | - | 2026-09-11 |
| - | 16665 | - | Reserved | - | - |
// source: IANA service name and port number registry
Which program uses port 16665, and is it reachable?
Linux
sudo ss -ltnup 'sport = :16665' # process listening on 16665
sudo lsof -nP -i :16665macOS
sudo lsof -nP -i :16665
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 16665 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 16665 netstat -ano | findstr :16665
From another machine
nmap -p 16665 -sV <host> nc -zv <host> 16665
Block it in the firewall
sudo ufw deny 16665/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 16665" -Direction Inbound -LocalPort 16665 -Protocol TCP -Action Block # Windows
What is port 16665 used for?
Port 16665 is assigned by IANA to axon-tunnel (Reliable multipath data transport for high latencies).
Is port 16665 TCP or UDP?
Port 16665 is registered for TCP.
Is it safe to open port 16665?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Patch VPN gateways quickly: they are a top initial access target.
How do I check if port 16665 is open?
On Linux run "ss -ltnup 'sport = :16665'", on macOS "lsof -nP -i :16665", and on Windows "netstat -ano | findstr :16665" to see the local process. From another machine, "nmap -p 16665 <host>" shows whether it is reachable.