http://sdz.tdct.org/sdz/les-sockets.html
pid_t getpid(void);
uid_t getuid(void);
int getaddrinfo(const char *node, const char *service, const struct addrinfo *hints, struct addrinfo **res);
int gettimeofday(struct timeval *tv, struct timezone *tz);
const char *inet_ntop(int af, const void *src, char *dst, socklen_t cnt);
int inet_pton(int af, const char * src, void *dst);
void exit(int status);
sighandler_t signal(int signum, sighandler_t handler);
unsigned int alarm(unsigned int nb_sec);
int setsockopt(int sockfd, int level, int optname, const void *optval, socklen_t optlen);
ssize_t recvmsg(int s, struct msghdr *msg, int flags);
ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen);
int socket(int domain, int type, int protocol);