more protection against socket when closing

test/CMakeLists.txt

@@ -37,12 +37,12 @@ set (SOURCES
   IXWebSocketTestConnectionDisconnection.cpp
   IXUrlParserTest.cpp
   IXWebSocketServerTest.cpp
-  IXWebSocketCloseTest.cpp
 )
 
 # Some unittest don't work on windows yet
 if (UNIX)
   list(APPEND SOURCES
+    IXWebSocketCloseTest.cpp
     IXDNSLookupTest.cpp
     cmd_websocket_chat.cpp
   )