Lock and wait

        Entry:
          AH = 11h
          AL = drive number or 0
          DX = number of seconds to wait
          ES:SI = Ethernet address or 0
          DS:BX -> 31-byte ASCIZ semaphore name
        Return:
          AL = status
            00h successful
            01h timeout
            02h server not responding
            03h invalid semaphore name
            04h semaphore list is full
            05h invalid drive ID
            06h invalid Ethernet address
            07h not logged in
            08h write to network failed
            09h semaphore already logged for this CPU