Int 21 Fn 5F34  u - Named Pipes - Local DOSsetnmphandstate                 [N]

   AX = 5F34h
   BX = handle
   CX = pipe mode bit mask
       bit 15: set if nonblocking, clear if blocking
       bit  8: set if read in message mode, clear if read in byte mode

Return: CF clear if successful
   CF set if error
       AX = error code

Note:  this function was introduced by LAN Manager but is also supported by
     the Novell DOS Named Pipe Extender, Banyan VINES, OS/2 Virtual DOS
     Machines, and others

See Also: AX=5F32h,AX=5F33h,AX=5F36h