User Manual

Boomer II User Manual & Integrator’s Guide
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SDK – SCR API
BM210012WT09 63 Wavenet Technology
Data Header
All data messages (MI, HR, OB, IB, TO_NET, FROM_NET) contain a
data header field. This field is used to route messages to the correct
server from client RPM devices. The data header is also sometimes
referred to as the session, and this is reflected in some of the NCL API
function parameters. For example, the szHostId parameter in
nclSendData and in the data header for the nclReceiveData functions.
This data header is represented in the SDK as a NULL terminated
string.
Refer to section Message Routing and Migration sub section SCR
Header charts on page x for the formatting of the header fields. How
the use of the Data Header field varies between the network types is
described below.
For DataTAC 4000 and 6000 networks, a host slot is used to route data
from the wireless client to the correct server. RPM devices can be
configured with up to five host slots, each routed to a different server
application. When the client application sends a message, the data
header is used to specify which host slot to send on, and hence which
server application the data will be sent to. The host slot is represented
by a single ASCII digit from 1 to 5. This digit must be given as the last
character of the data header. For example, a data header of I would
route the information on host slot 1, whereas a data header of TE3
would route the data on host slot 3.
For the DataTAC 5000 network, a 2-character session ID is used for
routing data from the wireless client to the correct server. RPM devices
may be configured with many sessions, each routed to different server
applications. The session ID is made up of any two characters from A
to Z or 0 to 9. When a client application sends data to a server
application, it must set the first two characters of the data header to the
session number. For example, a data header of Al routes data on
session A1, and a data header of TEI routes data on session TE.
To simplify porting of applications between different network types,
the use 3-character data headers, such as TEI. Using a data header of
this format, DataTAC 4000 and 6000 networks look only at the last
character of the data header and route on host slot 1, while a DataTAC
5000 network will look at the first two characters and route on session
TE. This allows the same data header to be used on all network types.
It is recommended that the data header is also set for messages from
server to client. This is not critical for routing messages back to the
client, but it is useful for the client to know on which session or host
slot (and therefore from which host) the data came.