#include <sys/types.h>
#include <netinet/in.h>
int main() {
    struct sockaddr_in      cs;                 /*  Communication parameters */
    int                     len;
    int                     sp = 0;             /*  Socket pointer */
    len = sizeof(cs);
    if (getpeername(sp,(struct sockaddr *)&cs,&len) < 0){
      exit(1);
    };
    printf("%s", (char *)strdup(inet_ntoa(cs.sin_addr)));
}