Class StunMappedAddressAttribute

source code

MAPPED-ADDRESS

The MAPPED-ADDRESS attribute indicates the mapped IP address and
port.  It consists of an eight bit address family, and a sixteen bit
port, followed by a fixed length value representing the IP address.

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x x x x x x x x|    Family     |           Port                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                             Address                           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The port is a network byte ordered representation of the mapped port.
The address family is always 0x01, corresponding to IPv4.  The first
8 bits of the MAPPED-ADDRESS are ignored, for the purposes of
aligning parameters on natural boundaries.  The IPv4 address is 32
bits.