Please permit only a single IP

[TomMettam]

While the STUN protocol does require the use of two IP addresses for determination of NAT type, in practice, most clients don't need or use this.

I would appreciate a configuration option "useSingleMode" or such, so that the server will not attempt to bind to a secondary IP.

I tried doing this, which matches what freeswitch does:

primary: {
        host: '127.0.0.1',
        port: '3478'
    },
    secondary: {
        host: '127.0.0.1',
        port: '3479'
    },
}

But this library attempts to bind to 127.0.0.1:3478 twice, which errors out.