I don’t remember all links, but here are some examples

https://github.com/ulion/libmicrohttpd/blob/master/src/examples/dual_stack_example.c

http://lists.gnu.org/archive/html/libmicrohttpd/2011-12/msg00003.html

in addition, we use MHD_OPTION_SOCK_ADDR in MHD daemons start,   and structs are different … sockaddr_in   and sockaddr_in6