+#include <sys/types.h> /* primitive system data types */
+#include <stdio.h> /* standard I/O library */
+#include <unistd.h> /* unix standard library */
+#include <string.h> /* C strings library */
+#include <errno.h> /* error definitions and routines */
+#include <sys/socket.h> /* socket constants, types and functions */
+#include <arpa/inet.h> /* IP addresses conversion utilities */
+#include <netdb.h> /* C resolver library */