NatTypeTester is a network diagnostic tool that identifies a host's network address translation (NAT) behavior by querying STUN servers. It classifies NAT types and tests connectivity across multiple transport layers, including UDP, TCP, TLS, and DTLS, to evaluate peer-to-peer communication capabilities.
The tool distinguishes itself by probing connectivity over four separate protocols—UDP, TCP, TLS-over-TCP, and DTLS-over-UDP—using STUN binding requests. This multi-protocol approach provides a comprehensive assessment of a host's ability to establish direct connections with other devices in various network environments.
NatTypeTester implements the STUN protocol to discover public IP addresses and detect NAT behavior, offering a complete NAT type classification algorithm. It supports cross-platform network diagnostics, enabling users to analyze transport-layer and IP-version compatibility across different operating systems.