diff --git a/src/a2io.h b/src/a2io.h
index 70a031c3..6e1196a6 100644
--- a/src/a2io.h
+++ b/src/a2io.h
@@ -146,6 +146,9 @@
 #  define a2open(path, flags, mode) _wsopen(path, flags, _SH_DENYNO, mode)
 #  define a2fopen(path, mode) _wfsopen(path, mode, _SH_DENYNO)
 // # define a2ftruncate(fd, length): We don't use ftruncate in Mingw build
+#  ifndef off_t 
+#  define off_t _off_t
+#  endif
 #  define a2_off_t off_t
 #elif defined(__ANDROID__) || defined(ANDROID)
 #  define a2lseek(fd, offset, origin) lseek64(fd, offset, origin)
@@ -201,4 +204,31 @@ extern int ftruncate64(int fd, off64_t length);
 #  define A2_BAD_FD -1
 #endif // !__MINGW32__
 
+#if defined(_MSC_VER)
+//  Present with their _ prefixes on MSVC
+#  define O_RDONLY        _O_RDONLY
+#  define O_WRONLY        _O_WRONLY
+#  define O_RDWR          _O_RDWR
+#  define O_APPEND        _O_APPEND
+#  define O_CREAT         _O_CREAT
+#  define O_EXCL          _O_EXCL
+#  define O_TRUNC         _O_TRUNC
+
+#  define STDIN_FILENO    _fileno(stdin)
+#endif
+
+#if defined(_MSC_VER)
+#  define a2_isatty  _isatty
+#  define a2_fileno  _fileno
+#  define a2_read    _read
+#  define a2_close   _close
+#  define a2_dup     _dup
+#else
+#  define a2_isatty  isatty
+#  define a2_fileno  fileno
+#  define a2_read    read
+#  define a2_close   close
+#  define a2_dub     dup
+#endif // !_MSC_VER
+
 #endif // D_A2IO_H
diff --git a/src/a2netcompat.h b/src/a2netcompat.h
index 8f0683d2..52e9ba87 100644
--- a/src/a2netcompat.h
+++ b/src/a2netcompat.h
@@ -84,7 +84,9 @@
 
 #ifndef HAVE_GETADDRINFO
 #  include "getaddrinfo.h"
-#  define HAVE_GAI_STRERROR
+#  ifndef HAVE_GAI_STRERROR
+#    define HAVE_GAI_STRERROR
+#  endif
 #endif // HAVE_GETADDRINFO
 
 #ifndef HAVE_GAI_STRERROR
diff --git a/src/gai_strerror.h b/src/gai_strerror.h
index effa6411..f88054af 100644
--- a/src/gai_strerror.h
+++ b/src/gai_strerror.h
@@ -56,7 +56,7 @@ extern "C" {
 /*
  * Functions.
  */
-#ifdef __STDC__
+#if defined(__STDC__) || defined(_MSC_VER)
 const char* gai_strerror(int);
 #else
 const char* gai_strerror();
diff --git a/src/getaddrinfo.c b/src/getaddrinfo.c
index 59c29e04..0946c040 100644
--- a/src/getaddrinfo.c
+++ b/src/getaddrinfo.c
@@ -124,7 +124,7 @@
 
 #ifndef HAVE_MEMCPY
 #  define memcpy(d, s, n) bcopy((s), (d), (n))
-#  ifdef __STDC__
+#  if defined(__STDC__) || defined(_MSC_VER)
 void* memchr(const void*, int, size_t);
 int memcmp(const void*, const void*, size_t);
 void* memmove(void*, const void*, size_t);
@@ -137,6 +137,10 @@ char* memset();
 #  endif /* not __STDC__ */
 #endif   /* not HAVE_MEMCPY */
 
+#if defined(_MSC_VER)
+#  define H_ERRNO_DECLARED 1
+#endif
+
 #ifndef H_ERRNO_DECLARED
 extern int h_errno;
 #endif
@@ -156,6 +160,11 @@ extern int h_errno;
 #  define N_(string) (string)
 #endif
 
+#if defined(_MSC_VER)
+# include <stdint.h>
+# define in_port_t uint16_t
+#endif
+
 /*
  * Error messages for gai_strerror().
  */
@@ -211,7 +220,7 @@ static pthread_mutex_t gai_mutex = PTHREAD_MUTEX_INITIALIZER;
 /*
  * Declaration of static functions.
  */
-#ifdef __STDC__
+#if defined(__STDC__) || defined(_MSC_VER)
 static int is_integer(const char*);
 static int is_address(const char*);
 static int itoa_length(int);
@@ -494,7 +503,9 @@ struct addrinfo** res;
   *res = head_res;
 
 end:
+#if !defined(_MSC_VER) // h_errno >> WSAGetLastError() ; not editable
   h_errno = saved_h_errno;
+#endif
 #ifdef ENABLE_PTHREAD
   pthread_mutex_unlock(&gai_mutex);
 #endif
@@ -588,7 +599,9 @@ int flags;
   }
 
 end:
+#if !defined(_MSC_VER) // h_errno >> WSAGetLastError() ; not editable
   h_errno = saved_h_errno;
+#endif
 #ifdef ENABLE_PTHREAD
   pthread_mutex_unlock(&gai_mutex);
 #endif
diff --git a/src/getaddrinfo.h b/src/getaddrinfo.h
index 7faaedc4..64eeccbf 100644
--- a/src/getaddrinfo.h
+++ b/src/getaddrinfo.h
@@ -41,7 +41,7 @@ extern "C" {
 #  include "config.h"
 #endif // HAVE_CONFIG_H
 
-#if defined(__MINGW32__) || defined(__MSVC__)
+#if defined(__MINGW32__) || defined(_MSC_VER)
 #  ifndef _WIN32_WINNT
 #    define _WIN32_WINNT 0x501
 #  endif // _WIN32_WINNT
@@ -240,7 +240,7 @@ extern "C" {
 #endif
 
 /* Nexenta OS(GNU/Solaris OS) defines `struct addrinfo' in netdb.h */
-#if !defined(__MINGW32__) && !defined(__sun) && !defined(_MSC_VER)
+#if !defined(__MINGW32__) && !defined(__sun) // && !defined(_MSC_VER)
 
 /*
  * struct addrinfo.
@@ -261,7 +261,7 @@ struct addrinfo {
 /*
  * Functions.
  */
-#ifdef __STDC__
+#if defined(__STDC__) || defined(_MSC_VER)
 const char* gai_strerror(int);
 void freeaddrinfo(struct addrinfo*);
 int getaddrinfo(const char*, const char*, const struct addrinfo*,
diff --git a/src/gettimeofday.c b/src/gettimeofday.c
index 8c7df499..76a53e12 100644
--- a/src/gettimeofday.c
+++ b/src/gettimeofday.c
@@ -23,7 +23,15 @@
  *  Danny Smith <dannysmith@users.sourceforge.net>
  */
 
-#include <sys/time.h>
+#include "config.h"
+
+#ifdef HAVE_SYS_TIME_H
+#  include <sys/time.h>
+#endif
+
+#ifdef HAVE_WINSOCK2_H
+#  include <winsock2.h>
+#endif /* HAVE_WINSOCK2_H */
 
 #if defined(__MINGW32__) || defined(_MSC_VER)
 
diff --git a/src/strptime.c b/src/strptime.c
index a27e6aa5..072010d0 100644
--- a/src/strptime.c
+++ b/src/strptime.c
@@ -54,11 +54,21 @@
 #endif // HAVE_ALLOCA_H
 
 #ifdef HAVE_MALLOC_H
+#  if defined(_MSC_VER)
+//   pull in alloca _alloca def
+#    define _CRT_INTERNAL_NONSTDC_NAMES 1 
+#  endif
 #  include <malloc.h>
 #endif // HAVE_MALLOC_H
 
 #include "strptime.h"
 
+#if defined(_MSC_VER)
+#  define tzname    _tzname
+#  define strncasecmp _strnicmp
+#  define strcasecmp _stricmp
+#endif
+
 static const char* abb_weekdays[] = {"Sun", "Mon", "Tue", "Wed",
                                      "Thu", "Fri", "Sat", NULL};
 
diff --git a/src/util.h b/src/util.h
index cdb6a950..0e567047 100644
--- a/src/util.h
+++ b/src/util.h
@@ -117,6 +117,11 @@ typedef SSIZE_T ssize_t;
 #endif
 
 
+#if defined(_MSC_VER)
+#  define strdup    _strdup
+#  define wdscup    _wcsdup
+#endif
+
 namespace util {
 
 extern const char DEFAULT_STRIP_CHARSET[];