man socket_mcloop4 () - set multicast loopback
NAME
socket_mcloop4 - set multicast loopback
SYNTAX
#include <socket.h>
int socket_mcloop4(int s,char loop);
DESCRIPTION
socket_mcloop4 activates multicast loopback for the socket s if loop is non-zero, and deactivates it otherwise. If loopback is activated, packets sent on this socket will be received on the same host.
If something goes wrong, socket_mcloop4 returns -1, setting errno appropriately.