* there is no guarantee that the external address will be valid for an extended period of time.
*
* @param mesh A handle which represents an instance of MeshLink.
* there is no guarantee that the external address will be valid for an extended period of time.
*
* @param mesh A handle which represents an instance of MeshLink.
*
* @return This function returns a pointer to a C string containing the discovered external address,
* or NULL if there was an error looking up the address.
*
* @return This function returns a pointer to a C string containing the discovered external address,
* or NULL if there was an error looking up the address.