NatTypeTester Channel Status CI Stun.Net RFC RFC 3489 RFC 5780 RFC 8489 Internet Protocol IPv4 IPv6 Transmission Protocol UDP TCP TLS-over-TCP Preview RFC3489 RFC5389 Binding Test Checking for UDP Connectivity with the STUN Server Mapping Behavior Determining NAT Mapping Behavior Filtering Behavior Determining NAT Filtering Behavior Combining Tests