socket_recv6 man page
socket_recv6 — receive a UDP datagram
ssize_t socket_recv6(int s, char* buf, size_t len,
char ip, uint16* port, uint32* scope_id);
socket_recv6 receives up to len bytes starting at buf from a UDP datagram coming in on the socket s. It writes the UDP port to port and the IP address to ip, and returns the number of bytes actually received (or -1 if anything went wrong).
For link-local addresses, scope_id will become the network interface number, which can be translated into the name of the interface ("eth0") with socket_getifname.
socket_recv6 returns the number of bytes in the datagram if one was received. If not, it returns -1 and sets errno appropriately.
s = socket_tcp4();
len = socket_recv6(s,buf,sizeof(buf),ip,&p,&scope_id);