Add Windows and Visual Studio support

src/tls_ext.c

@@ -1,4 +1,4 @@
-/*
+/*
  *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
  *
  *  Licensed under the Apache License, Version 2.0 (the License); you may
@@ -13,12 +13,19 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
 #include <fcntl.h>
+#ifdef WIN32
+
+#include <winsock2.h>		
+
+
+#else
+#include <unistd.h>
 #include <sys/types.h>
 #include <arpa/inet.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
+#endif
 #include <gmssl/rand.h>
 #include <gmssl/x509.h>
 #include <gmssl/error.h>