CBXi IP Controller |
BACnet Networking
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BACNET'S CLIENT / SERVER NATURE
BACnet
uses a “
Client/Server
" architecture. BACnet messages are called service requests. A
Client
machine
sends a service request to a
Server
machine that then performs the service and reports the result to the
Client
.
Example:
A simple device such as a fixed function VAV controller would typically act as Server.
Front-end software running on a PC would act as a
BACnet
Client reading status values from the VAV and
changing set-points.
Notes
:
Server
devices cannot initiate communication. Higher end embedded controllers generally include both
server
and
client
functionality. This allows them to share information such as outside temperature with
each other or send alarms to a
PC
.
BACnet
currently defines 35 message types that are divided into 5 groups or classes. For example, one
class contains messages for accessing and manipulating the properties of the objects described above.
A common message type is the "
ReadProperty
" service request. This message causes the server
machine to locate the requested property of the requested object and send its value back to the client.
Other classes of services deal with: alarms and events, file uploading and downloading, managing the
operation of remote devices and virtual terminal functions.
NETWORK TYPES
BACnet
messages can be carried over the following types of network:
•
Ethernet
•
ARCnet
•
Master-Slave/Token-Passing (
MS/TP
)
•
Point-to-Point (PTP)
•
LON
•
BACnet/IP
