Resolve bugs based on unreliable bytesReceived value.

lib/windows/winlean.nim

@@ -759,6 +759,7 @@ const
   WSAENETRESET* = 10052
   WSAETIMEDOUT* = 10060
   ERROR_NETNAME_DELETED* = 64
+  STATUS_PENDING* = 0x103
 
 proc createIoCompletionPort*(FileHandle: Handle, ExistingCompletionPort: Handle,
                              CompletionKey: ULONG_PTR,
@@ -775,6 +776,12 @@ proc getOverlappedResult*(hFile: Handle, lpOverlapped: POVERLAPPED,
               lpNumberOfBytesTransferred: var DWORD, bWait: WINBOOL): WINBOOL{.
     stdcall, dynlib: "kernel32", importc: "GetOverlappedResult".}
 
+# this is copy of HasOverlappedIoCompleted() macro from <winbase.h>
+# because we have declared own OVERLAPPED structure with member names not
+# compatible with original names.
+template hasOverlappedIoCompleted*(lpOverlapped): bool =
+  (cast[uint](lpOverlapped.internal) != STATUS_PENDING)
+
 const
  IOC_OUT* = 0x40000000
  IOC_IN*  = 0x80000000