INT 7A - Novell NetWare - SPX Driver - ESTABLISH SPX CONNECTION
        BX = 0011h
        AL = retry count
        AH = watchdog flag
        ES:SI -> Event Control Block (see BX=0003h)
Return: AL = status
            00h attempting to contact destination socket
            EFh local connection table full
            FDh buffer size not 42 or fragment count not 1
            FFh sending socket not open
        DX = assigned connection ID number
Desc:   attempt to establish a connection with a listening socket
Notes:  there should always be at least two SPX ECB's listening to a socket, so
          that NetWare can perform its internal packet exchanges
        the first fragment should start with a SPX header.  Fill in all
          destination addresses.
        this function is supported by Advanced NetWare 2.1+
SeeAlso: BX=0000h,BX=0012h,BX=0013h,BX=0014h,BX=0015h

Format of SPX header:
Offset  Size    Description
 00h    WORD    (big-endian) checksum
 02h    WORD    (big-endian) length in bytes of total packet
 04h    BYTE    transport control
 05h    BYTE    packet type (see INT 7A/BX=0003h)
 06h 10 BYTEs   destination internet address
 10h    WORD    (big-endian) destination socket
 12h 10 BYTEs   source internet address
 1Ch    WORD    (big-endian) source socket
 1Eh    BYTE    connection control (see below)
 1Fh    BYTE    datastream type
                FEh terminate connection request packet
                FFh terminate connection acknowledgement packet
                other user-defined, ignored by SPX
 20h    WORD    (big-endian) source connection ID
 22h    WORD    (big-endian) destination connection ID
 24h    WORD    (big-endian) sequence number
 26h    WORD    (big-endian) acknowledge number
 28h    WORD    (big-endian) allocation number

Bitfield for connection control:
 bits 3-0 unused???
 bit 4  end of message
 bit 5  reserved
 bit 6  acknowledgement required
 bit 7  system packet

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