Topic       : TOS - The Operating System
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View Ref-File13.13.3.4  Request/Reply protocol                                  TOS

Two further messages were introduced to enable a general data 
exchange:

#define ACC_REQUEST     0x480
#define ACC_REPLY       0x481

 ACC_REQUEST

   With this message one requests a service from another application. 
   The makeup of this message is as follows:

         msg[0]:     ACC_REQUEST (0x480)
         msg[1]:     Application ID of the sender
         msg[2]:     0
         msg[3]:     The high-byte is free for application-specific
                     information, and in the low-byte the type of the
                     data is coded that are sent with this message:
                     0x01  String, i.e. msg[4]+msg[5] is a
                           pointer to the string
                     0x02  EEnv-string, i.e. msg[4]+msg[5] is
                           a pointer to the Env-string (multiple
                           strings separated by '\0', with a
                           terminating double '\0'-bytes)
                     0x03  Binary data, i.e. msg[4]+msg[5] is
                           a pointer to the binary data. In this
                           case the receiver naturally has to be
                           aware of the data structure! (Local
                           type differentiation is possible by means
                           of the high-byte, for instance)
                     0x04  Code, i.e. msg[4] to msg[7] directly
                           contain the data (useful for transmission
                           of data amounts up to 8 bytes)
         msg[4,5]:   Pointer to the data (except type 0x04)
         msg[6,7]:   Length of data area, incl. possible '\0'-bytes
                     (except type 0x04)

   There are two different options for replying to this message:

      . ACC_ACK with msg[3]=0, if the receiving application cannot 
        process this message

      . ACC_REPLY, if the message could be processed and a reply has 
        been sent back

 ACC_REPLY

   A successful ACC_REQUEST request is answered with this message. The 
   makeup of this message is as follows:

               msg[0]:     ACC_REPLY (0x481)
               msg[1]:
                   .
                   .       see ACC_REQUEST!
                   .
               msg[7]:

Applications that support the protocol elements described above have 
to contain the Extended feature 'RQ' in their XDSC description.