+#include <sys/types.h> /* primitive system data types */
+#include <sys/stat.h> /* file characteristics constants and functions */
+#include <stdlib.h> /* C standard library */
+#include <stdio.h> /* standard I/O library */
+#include <unistd.h> /* unix standard library */
+#include <arpa/inet.h> /* IP addresses conversion utilities */
+#include <netdb.h> /* C resolver library */
+#include <netinet/tcp.h> /* TCP socket option */
+