BACnet通讯分析.docx
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BACnet通讯分析.docx
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BACnet通讯分析
BACnet通讯
1、概述.
系统实现基于BACnet/IP(又称B/IP)网络进行通讯。
BACnet虚拟链路层(BVLL)提供了BACnet网络层和某指定的通讯子系统的接口,本文指定了BACnet虚拟链路控制(BVLC)要求支持的定向和广播信息。
本实现关于BACnet协议定义主要可分为三层:
B/IP网络虚拟层,BACnet网络层和BACnet应用层。
B/IP提供了TCP/IP一样的通讯结构,采用UDP的通讯方式。
本文接下来将对此三层结构进行详细的讲解。
其文本协议的大致格式如下:
BACnet/IP
BACnet网络层
BACnet应用层
BVLCType
BVLCFunction
Length
NPDU
APDU
NPDU:
BACnet网络层数据结构,下文进行详细的讲解
APDU:
BACnet应用层数据结构,下文进行详细的讲解
2、BACnet/IP.
BVLCType:
0x81,代表BACnet/IP网络
BVLCFunction:
指定报文的类型,何种作用;本应用使用的报文类型分为两种:
0A:
点对点通讯
0B:
广播通信
Length:
指定报文的长度,包括BVLCType、BVLCFunction以及本身在内
NPDU:
根据不同情况,报文长短不同,见下文的解析。
APDU:
根据NPDU不同以及不同的请求,报文不同,见下文的解析。
3、BACnetNPDU结构.
版本信息
1Byte
Version
控制字
1Byte
Control
目标网络号
2Bytes
DNET
目标网络长度
1Byte
DLEN
目标地址
可变长度
DADR
原网络号
2Bytes
SNET
原网络长度
1Byte
SLEN
原地址
可变
SNET
路由数目
1Byte
HopCount
消息类型
1Byte
MessageType
卖方ID
2Bytes
VendorID
应用层信息
可变
APDU
版本信息:
默认0x01
控制字:
BIT7:
1表示MessageType存在,为0时MessageType不存在
BIT6:
保留,为0BIT5:
1表示DNETDLENHopCount存在,当DLEN为0时表明广播网络DADR不存在;0表示DNETDLENDADRHopCount不存在BIT4:
保留,为0BIT3:
1表示SNETSLEN存在,当SLEN为0时表明无效SADR不存在;0表示SNETSLENSADRHopCount不存在
BIT2:
1表示为一个需确认的请求数据单元,一复杂ACK数据单元或一网络层信息非reply的;0表示除去上述情形的数据单元
BIT1、0:
网络优先级
11=LifeSafetymessage
10=CriticalEquipmentmessage
01=Urgentmessage00=Normalmessage目标网络号:
FFFF的时候表示广播目标长度:
表示DADR的长度目标地址:
目标网络MAC地址原网络号:
同目标网络号原网络长度:
表示SADR的长度原地址:
原网络的MAC地址路由数目:
数据需要经过的路由个数,当不存在DNET的时候,需设置为FF消息类型:
X'00':
Who-Is-Router-To-Network
X'01':
I-Am-Router-To-NetworkX'02':
I-Could-Be-Router-To-NetworkX'03':
Reject-Message-To-Network
X'04':
Router-Busy-To-NetworkX'05':
Router-Available-To-NetworkX'06':
Initialize-Routing-Table
X'07':
Initialize-Routing-Table-AckX'08':
Establish-Connection-To-NetworkX'09':
Disconnect-Connection-To-NetworkX'0A'toX'7F':
ReservedforusebyASHRAEX'80'toX'FF':
Availableforvendorproprietarymessages卖方ID:
当控制字的BIT7为1并且消息类型为X'80'toX'FF':
的时候,才会存在
本次开发没有用到,不再解释
本次应用中控制字只用到0x20和0x04两种,前者为广播查询设备,后者微点对对取设备数据或属性。
4、BACnetAPDU结构:
(应用层协议数据单元)
BACnet网络层数据主要分为一下几种:
BACnetPDU:
:
=CHOICE
{confirmed-request-PDU[0]BACnet-Confirmed-Request-PDU,
对于本次应用,主要用到了
BACnet-Confirmed-Request-PDU(需确认的请求协议数据单元)
BACnet-Unconfirmed-Request-PDU(无需确认的请求协议数据单元)
BACnet-ComplexACK-PDU(复杂的ACK命令)
BACnet-Error-PDU(报错的协议数据单元)
对于上述几种数据的分类主要根据pdutype(下文进行讲解)进行判定。
4.1.BACnet-Confirmed-Request-PDU的结构:
BACnet-Confirmed-Request-PDU:
:
=SEQUENCE{
pdu-typesegmented-messagemore-follows
[0]Unsigned(0..15),--0forthisPDUtype
[1]BOOLEAN,
[2]BOOLEAN,
segmented-response-accepted[3]BOOLEAN,
[4]
Unsigned(0..3),--mustbesettozero
[5]Unsigned(0..7),--asper20.1.2.4
[6]Unsigned(0..15),--asper20.1.2.5
[7]Unsigned(0..255),
[8]Unsigned(0..255)OPTIONAL,--onlyifsegmentedmsg
[9]Unsigned(1..127)OPTIONAL,--onlyifsegmentedmsg
[10]BACnetConfirmedServiceChoice,
[11]BACnet-Confirmed-Service-RequestOPTIONAL
BIT7
BIT6BIT5BIT4
BIT3
BIT2
BIT1
BIT0
PDUTYPE
SEG
MOR
SA
0
0
MaxSegs
MaxResp
InvokeID
SequenceNumber(onlypresentbySEG==1)
ProposedWindowSize(onlypresentbySEG==1)
ServiceChioce
ServiceRequest……
}
PDUType
SEG
0
0
1
(BACnet-Confirmed-Service-Request-PDU)
(UnsegmentedRequest)
(SegmentedRequest)
(NoMoreSegmentsFollow)
(MoreSegmentsFollow)
(SegmentedResponsenotaccepted)
(SegmentedResponseaccepted)
(Numberofresponsesegmentsacceptedper20.1.2.4)
(SizeofMaximumAPDUacceptedper20.1.2.5)
OnlypresentifSEG=1
OnlypresentifSEG=1BACnetConfirmedServiceChoice
SEG:
指出当前的数据单元是否为完整的还是为一部分分段信息
MOR:
指出是否还有更多的分段信息
SA:
为1时指出将收到一个复杂的回应(complexack)
MaxSegs:
指出设备将要接收到多少分段信息
B'000'
Unspecifiednumberofsegmentsaccepted.
B'001'
2segmentsaccepted.
B'010'
4segmentsaccepted.
B'011'
8segmentsaccepted.
B'100'
16segmentsaccepted.
B'101'
32segmentsaccepted.
B'110'
64segmentsaccepted.
B'111'
Greaterthan64segmentsaccepted.
MaxResp:
指出将收到的(APDU)最大长度
B'0000'UptoMinimumMessageSize(50octets)
B'0001'Upto128octets
B'0010'Upto206octets(fitsinaLonTalkframe)
B'0011'Upto480octets(fitsinanARCNETframe)
B'0100'Upto1024octets
B'0101'Upto1476octets(fitsinanISO8802-3frame)
InvokeID:
调用者ID
ServiceChioce:
此处表明次报文的作用,详见BACnetConfirmedServiceChoice
ServiceRequest:
根据BACnetConfirmedServiceChoice不同而结构不同,详见
BACnet-Confirmed-Service-Request
BACnetConfirmedServiceChoice:
:
=枚举类型
{
--AlarmandEventServicesacknowledgeAlarm(0),
confirmedCOVNotification
(1),
confirmedEventNotification
(2),
getAlarmSummary(3),
getEnrollmentSummary(4),
getEventInformation(29),
subscribeCOV(5),
subscribeCOVProperty(28),
lifeSafetyOperation(27),
--FileAccessServicesatomicReadFile(6),
atomicWriteFile(7),
--ObjectAccessServicesaddListElement(8),
removeListElement(9),
createObject(10),
deleteObject(11),
readProperty(12),
readPropertyConditional(13),
readPropertyMultiple(14),
readRange(26),
writeProperty(15),
writePropertyMultiple(16),}上述标记为红色的表示本次应用中所用到的,所以只对这些进行讲解。
可以根据BACnetConfirmedServiceChoice找到相对应的Request或者Ack的数据的结构BACnet-Confirmed-Service-Request:
:
=CHOICE//对应上面的Choice
{
--AlarmandEventServices
acknowledgeAlarmconfirmedCOVNotificationconfirmedEventNotification
[0]AcknowledgeAlarm-Request,
[1]ConfirmedCOVNotification-Request,
[2]ConfirmedEventNotification-Request,
getAlarmSummaryconveysnoparameters
[4]
getEnrollmentSummarygetEventInformationsubscribeCOVsubscribeCOVPropertylifeSafetyOperation
--FileAccessServicesatomicReadFileatomicWriteFile
--ObjectAccessServices
addListElement
GetEnrollmentSummary-Request,
[29]GetEventInformation-Request,
[5]SubscribeCOV-Request,
[28]SubscribeCOVProperty-Request,
[27]LifeSafetyOperation-Request,
[6]AtomicReadFile-Request,
[7]AtomicWriteFile-Request,
[8]AddListElement-Request,
[9]
removeListElementcreateObjectdeleteObjectreadPropertyreadPropertyConditionalreadPropertyMultiplereadRangewritePropertywritePropertyMultiple
RemoveListElement-Request,
[10]CreateObject-Request,
[11]DeleteObject-Request,
[12]ReadProperty-Request,
[13]ReadPropertyConditional-Request,
[14]ReadPropertyMultiple-Request,
[26]ReadRange-Request,
[15]WriteProperty-Request,
[16]WritePropertyMultiple-Request,}上述标记为红色的既是针对BACnetConfirmedServiceChoice所用到的数据结构。
ReadProperty-Request:
:
=SEQUENCE//读数据请求和读数据回答
{
objectIdentifier
propertyIdentifierpropertyArrayIndex
[0]BACnetObjectIdentifier,
[1]BACnetPropertyIdentifier,
[2]UnsignedOPTIONAL--usedonlywitharraydatatype
}
ReadPropertyMultiple-Request:
:
=SEQUENCE
{
listOfReadAccessSpecsSEQUENCEOFReadAccessSpecification
}
ReadAccessSpecification:
:
=SEQUENCE{
objectIdentifierlistOfPropertyReferences
[0]BACnetObjectIdentifier,
[1]SEQUENCEOFBACnetPropertyReference
}
BACnetPropertyReference:
:
=SEQUENCE{
propertyIdentifier[0]BACnetPropertyIdentifier,
propertyArrayIndex[1]UnsignedOPTIONAL--usedonlywitharraydatatype
--ifomittedwithanarraytheentirearrayisreferenced}
BACnetPropertyIdentifier:
:
=ENUMERATED{
accepted-modes
(175),
acked-transitions
(0),
ack-required
(1),
action
(2),
action-text
(3),
active-text
(4),
active-vt-sessions
(5),
active-cov-subscriptions
(152),
adjust-value
(176),
alarm-value
(6),
alarm-values
(7),
all
(8),
all-writes-successful
(9),
apdu-segment-timeout
(10),
apdu-timeout
(11),
application-software-version
(12),
firmware-revision
(44),
archive
(13),
attempted-samples
(124),
list-of-group-members
(53),
list-of-object-property-references
(54),
list-of-session-keys
(55),
local-date
(56),
local-time
(57),
location
(58),
maintenance-required
(158),
manipulated-variable-reference
(60),
manual-slave-address-binding
(170),
maximum-output
(61),
maximum-value
(135),
maximum-value-timestamp
(149),
max-apdu-length-accepted
(62),
max-info-frames
(63),
max-master
(64),
max-pres-value
(65),
max-segments-accepted
(167),
member-of
(159),
minimum-off-time
(66),
minimum-on-time
(67),
minimum-output
(68),
event-state
(36),
model-name
(70),
number-of-APDU-retries
(73),
object-identifier
(75),
object-list
(76),
object-name
(77),
object-property-reference
(78),
object-type
(79),
operation-expected
(161),
optional
(80),
out-of-service
(81),
output-units
(82),
--seeevent-parameters
(83),
polarity
(84),
prescale
(185),
present-value
(85),
priority
(86),
pulse-rate
(186),
priority-array
(87),
priority-for-writing
(88),
protocol-object-types-supported
(96),
protocol-revision
(139),
protocol-services-supported
(97),
protocol-version
(98),
reliability
(103),
relinquish-default
(104),
schedule-default
(174),
segmentation-supported
(107),
state-text
(110),
status-flags
(111),
stop-time
(143),
stop-when-full
(144),
system-status
(112),
tracking-value
(164),
units
(117),
variance-value
(151),
vendor-identifier
(120),
vendor-name
(121),
--seedatabase-revision
(155),
}
上述标记为红色者既是本次应用所用到的属性对象
BACnetObjectIdentifier的编码分为两个部分:
Objecttype
InstanceNumber
占用了10Bits
占用了22Bits
ObjectType的表格如下:
BACnetObjectTypesSupported:
:
=BITSTRING{
--accumulator
(23),
analog-input
(0),
analog-output
(1),
analog-value
(2),
DEVICE:
:
=SEQUENCE
{
object-identifierobject-nameobject-typesystem-statusvendor-namevendor-identifiermodel-namefirmware-revisionapplication-software-versionlocationdescriptionprotocol-versionprotocol-revisionprotocol-services-supportedprotocol-object-types-supportedobject-list
max-APDU-length-supportedsegmentation-supportedvt-classes-supportedactive-vt-sessionslocal-timelocal-dateutc-offset
--averaging
(18),
binary-input
(3)
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