pystun3

Discover NAT type using STUN protocol

TLDR

Check NAT type

$ pystun3

Use specific STUN server

$ pystun3 -H [stun.example.com]

Specify source port

$ pystun3 -p [54320]

Use specific interface

$ pystun3 -i [192.168.1.100]

Verbose output

$ pystun3 -v

JSON output

$ pystun3 --json

SYNOPSIS

pystun3 [-H server] [-p port] [-i ip] [options]

pystun3 is a STUN (Session Traversal Utilities for NAT) client that discovers the type of NAT between a host and the internet. It communicates with a STUN server to determine the NAT classification (full cone, restricted cone, port restricted, or symmetric) and reports the external IP address and mapped port.
Understanding NAT type is essential for configuring VoIP, video conferencing, and peer-to-peer applications that require direct connections between hosts. The tool can target specific STUN servers, bind to particular network interfaces, and output results in JSON format for scripting.

PARAMETERS

-H HOST

STUN server hostname.

-p PORT

Source port.

-i IP

Source IP address.

-v

Verbose output.

--json

JSON output format.

-P PORT

STUN server port.

CAVEATS

Requires network access. STUN server must be reachable. NAT types vary.

HISTORY

pystun3 is a Python 3 port of pystun, implementing STUN (Session Traversal Utilities for NAT) client functionality.