man socket_mcjoin4 () - join a multicast group
NAME
socket_mcjoin4 - join a multicast group
SYNTAX
#include <socket.h>
int socket_mcjoin4(int s,const char groupip[4],const char interface[4]);
DESCRIPTION
socket_mcjoin4 joins the IPv4 multicast group groupip on interface.
If something goes wrong, socket_mcjoin4 returns -1, setting errno appropriately.