diff --git a/ares/configure.ac b/ares/configure.ac
index d4bd4d284fbdf1642e3bd356cc240a97d414a0ca..eda89eb093c0b936d56a43bc67395ec3f2668b9b 100644
--- a/ares/configure.ac
+++ b/ares/configure.ac
@@ -536,6 +536,7 @@ CURL_CHECK_FUNC_SEND
 CURL_CHECK_MSG_NOSIGNAL
 
 CARES_CHECK_FUNC_CLOSESOCKET
+CARES_CHECK_FUNC_CLOSESOCKET_CAMEL
 CARES_CHECK_FUNC_FCNTL
 CARES_CHECK_FUNC_FREEADDRINFO
 CARES_CHECK_FUNC_GETADDRINFO
diff --git a/ares/m4/cares-functions.m4 b/ares/m4/cares-functions.m4
index 40545d940dc820bc9b5d309b1473c83f6146c9cc..1da3f5a534e482d67aaee2a01b59e0073d9be4bd 100644
--- a/ares/m4/cares-functions.m4
+++ b/ares/m4/cares-functions.m4
@@ -16,7 +16,7 @@
 #***************************************************************************
 
 # File version for 'aclocal' use. Keep it a single number.
-# serial 30
+# serial 31
 
 
 dnl CARES_INCLUDES_ARPA_INET
@@ -434,6 +434,96 @@ AC_DEFUN([CARES_CHECK_FUNC_CLOSESOCKET], [
 ])
 
 
+dnl CARES_CHECK_FUNC_CLOSESOCKET_CAMEL
+dnl -------------------------------------------------
+dnl Verify if CloseSocket is available, prototyped, and
+dnl can be compiled. If all of these are true, and
+dnl usage has not been previously disallowed with
+dnl shell variable cares_disallow_closesocket_camel,
+dnl then HAVE_CLOSESOCKET_CAMEL will be defined.
+
+AC_DEFUN([CARES_CHECK_FUNC_CLOSESOCKET_CAMEL], [
+  AC_REQUIRE([CARES_INCLUDES_SYS_SOCKET])dnl
+  #
+  tst_links_closesocket_camel="unknown"
+  tst_proto_closesocket_camel="unknown"
+  tst_compi_closesocket_camel="unknown"
+  tst_allow_closesocket_camel="unknown"
+  #
+  AC_MSG_CHECKING([if CloseSocket can be linked])
+  AC_LINK_IFELSE([
+    AC_LANG_PROGRAM([[
+      $cares_includes_sys_socket
+    ]],[[
+      if(0 != CloseSocket(0))
+        return 1;
+    ]])
+  ],[
+    AC_MSG_RESULT([yes])
+    tst_links_closesocket_camel="yes"
+  ],[
+    AC_MSG_RESULT([no])
+    tst_links_closesocket_camel="no"
+  ])
+  #
+  if test "$tst_links_closesocket_camel" = "yes"; then
+    AC_MSG_CHECKING([if CloseSocket is prototyped])
+    AC_EGREP_CPP([CloseSocket],[
+      $cares_includes_sys_socket
+    ],[
+      AC_MSG_RESULT([yes])
+      tst_proto_closesocket_camel="yes"
+    ],[
+      AC_MSG_RESULT([no])
+      tst_proto_closesocket_camel="no"
+    ])
+  fi
+  #
+  if test "$tst_proto_closesocket_camel" = "yes"; then
+    AC_MSG_CHECKING([if CloseSocket is compilable])
+    AC_COMPILE_IFELSE([
+      AC_LANG_PROGRAM([[
+        $cares_includes_sys_socket
+      ]],[[
+        if(0 != CloseSocket(0))
+          return 1;
+      ]])
+    ],[
+      AC_MSG_RESULT([yes])
+      tst_compi_closesocket_camel="yes"
+    ],[
+      AC_MSG_RESULT([no])
+      tst_compi_closesocket_camel="no"
+    ])
+  fi
+  #
+  if test "$tst_compi_closesocket_camel" = "yes"; then
+    AC_MSG_CHECKING([if CloseSocket usage allowed])
+    if test "x$cares_disallow_closesocket_camel" != "xyes"; then
+      AC_MSG_RESULT([yes])
+      tst_allow_closesocket_camel="yes"
+    else
+      AC_MSG_RESULT([no])
+      tst_allow_closesocket_camel="no"
+    fi
+  fi
+  #
+  AC_MSG_CHECKING([if CloseSocket might be used])
+  if test "$tst_links_closesocket_camel" = "yes" &&
+     test "$tst_proto_closesocket_camel" = "yes" &&
+     test "$tst_compi_closesocket_camel" = "yes" &&
+     test "$tst_allow_closesocket_camel" = "yes"; then
+    AC_MSG_RESULT([yes])
+    AC_DEFINE_UNQUOTED(HAVE_CLOSESOCKET_CAMEL, 1,
+      [Define to 1 if you have the CloseSocket camel case function.])
+    ac_cv_func_closesocket_camel="yes"
+  else
+    AC_MSG_RESULT([no])
+    ac_cv_func_closesocket_camel="no"
+  fi
+])
+
+
 dnl CARES_CHECK_FUNC_FCNTL
 dnl -------------------------------------------------
 dnl Verify if fcntl is available, prototyped, and
diff --git a/configure.ac b/configure.ac
index 3dfd087ac4fca5a596aea2460722db352e8d9c4c..c141e7bd63d97f4c6fd6f6605441fb237c3b5766 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2001,6 +2001,7 @@ CURL_CHECK_MSG_NOSIGNAL
 
 CURL_CHECK_FUNC_ALARM
 CURL_CHECK_FUNC_CLOSESOCKET
+CURL_CHECK_FUNC_CLOSESOCKET_CAMEL
 CURL_CHECK_FUNC_FCNTL
 CURL_CHECK_FUNC_FDOPEN
 CURL_CHECK_FUNC_FREEADDRINFO
diff --git a/m4/curl-functions.m4 b/m4/curl-functions.m4
index 891493a0ac43ebcfd5bd90040638171ed07c2a6a..df750478ced4de1bfd38cf77351796574ee7ba8d 100644
--- a/m4/curl-functions.m4
+++ b/m4/curl-functions.m4
@@ -22,7 +22,7 @@
 #***************************************************************************
 
 # File version for 'aclocal' use. Keep it a single number.
-# serial 49
+# serial 50
 
 
 dnl CURL_INCLUDES_ARPA_INET
@@ -692,6 +692,96 @@ AC_DEFUN([CURL_CHECK_FUNC_CLOSESOCKET], [
 ])
 
 
+dnl CURL_CHECK_FUNC_CLOSESOCKET_CAMEL
+dnl -------------------------------------------------
+dnl Verify if CloseSocket is available, prototyped, and
+dnl can be compiled. If all of these are true, and
+dnl usage has not been previously disallowed with
+dnl shell variable curl_disallow_closesocket_camel,
+dnl then HAVE_CLOSESOCKET_CAMEL will be defined.
+
+AC_DEFUN([CURL_CHECK_FUNC_CLOSESOCKET_CAMEL], [
+  AC_REQUIRE([CURL_INCLUDES_SYS_SOCKET])dnl
+  #
+  tst_links_closesocket_camel="unknown"
+  tst_proto_closesocket_camel="unknown"
+  tst_compi_closesocket_camel="unknown"
+  tst_allow_closesocket_camel="unknown"
+  #
+  AC_MSG_CHECKING([if CloseSocket can be linked])
+  AC_LINK_IFELSE([
+    AC_LANG_PROGRAM([[
+      $curl_includes_sys_socket
+    ]],[[
+      if(0 != CloseSocket(0))
+        return 1;
+    ]])
+  ],[
+    AC_MSG_RESULT([yes])
+    tst_links_closesocket_camel="yes"
+  ],[
+    AC_MSG_RESULT([no])
+    tst_links_closesocket_camel="no"
+  ])
+  #
+  if test "$tst_links_closesocket_camel" = "yes"; then
+    AC_MSG_CHECKING([if CloseSocket is prototyped])
+    AC_EGREP_CPP([CloseSocket],[
+      $curl_includes_sys_socket
+    ],[
+      AC_MSG_RESULT([yes])
+      tst_proto_closesocket_camel="yes"
+    ],[
+      AC_MSG_RESULT([no])
+      tst_proto_closesocket_camel="no"
+    ])
+  fi
+  #
+  if test "$tst_proto_closesocket_camel" = "yes"; then
+    AC_MSG_CHECKING([if CloseSocket is compilable])
+    AC_COMPILE_IFELSE([
+      AC_LANG_PROGRAM([[
+        $curl_includes_sys_socket
+      ]],[[
+        if(0 != CloseSocket(0))
+          return 1;
+      ]])
+    ],[
+      AC_MSG_RESULT([yes])
+      tst_compi_closesocket_camel="yes"
+    ],[
+      AC_MSG_RESULT([no])
+      tst_compi_closesocket_camel="no"
+    ])
+  fi
+  #
+  if test "$tst_compi_closesocket_camel" = "yes"; then
+    AC_MSG_CHECKING([if CloseSocket usage allowed])
+    if test "x$curl_disallow_closesocket_camel" != "xyes"; then
+      AC_MSG_RESULT([yes])
+      tst_allow_closesocket_camel="yes"
+    else
+      AC_MSG_RESULT([no])
+      tst_allow_closesocket_camel="no"
+    fi
+  fi
+  #
+  AC_MSG_CHECKING([if CloseSocket might be used])
+  if test "$tst_links_closesocket_camel" = "yes" &&
+     test "$tst_proto_closesocket_camel" = "yes" &&
+     test "$tst_compi_closesocket_camel" = "yes" &&
+     test "$tst_allow_closesocket_camel" = "yes"; then
+    AC_MSG_RESULT([yes])
+    AC_DEFINE_UNQUOTED(HAVE_CLOSESOCKET_CAMEL, 1,
+      [Define to 1 if you have the CloseSocket camel case function.])
+    ac_cv_func_closesocket_camel="yes"
+  else
+    AC_MSG_RESULT([no])
+    ac_cv_func_closesocket_camel="no"
+  fi
+])
+
+
 dnl CURL_CHECK_FUNC_FCNTL
 dnl -------------------------------------------------
 dnl Verify if fcntl is available, prototyped, and