WO2018228708A1

WO2018228708A1 - Method, device and system for concealed communication with devices in different networks in a building automation environment

Info

Publication number: WO2018228708A1
Application number: PCT/EP2017/064842
Authority: WO
Inventors: Pratima GOKHALE; Bernhard Isler; Sudhir JAISWAL
Original assignee: Siemens Schweiz AG
Current assignee: Siemens Schweiz AG
Priority date: 2017-06-16
Filing date: 2017-06-16
Publication date: 2018-12-20
Anticipated expiration: 2019-12-16

Abstract

A method of communicating with devices in different networks in a building automation system (200), the building automation system (200) comprising a first network of devices (202) and a second network of devices (204), and a shared device (240) connected to both the first network and the second network. The method includes routing a message received on a port of the share d device (240) directly to an application (218) on the shared device (240), without routing the message to another port of the shared device (240). The method also includes routing a further message sent by the application (218) to one of the ports of the shared device (240), based on a destination network number of the further message. Further, the method includes duplicating and routing a global broadcast message sent by the application (218) to each of the ports of the shared device (240).

Description

Method, Device and System for concealed communication with devices in different networks in a building automation envi- ronment

The present invention relates to communication between devices in a building automation environment. The building automation environment typically includes inte^¬ grated and controlled systems that are arranged and organized into one or more networks of devices, where the devices com^¬ municate to each other according to a network protocol, such as the Building Automation and Control Networks (BACnet, ANSI/ASHRAE Standard 135) protocol.

Devices communicating with the BACnet protocol are known as BACnet devices and multiple BACnet devices in two or more BACnet networks constitute a BACnet internetwork. Generally, messages between BACnet devices in different BACnet networks are routed by a BACnet router. The BACnet router facilitates communication by forwarding unicast and global or directed broadcast messages across the BACnet networks. In certain scenarios, it is preferable that the messages between BACnet devices in a BACnet network be restricted to the same network and not be visible to other networks. For example, if a BAC^¬ net device in a network has resource constraints, it may be preferable to restrict irrelevant or broadcast messages from another network, to avoid processing by the resource con- strained BACnet device. Accordingly, it is preferable not to receive the irrelevant or broadcast messages.

In another example, a BACnet internetwork may sometimes in^¬ clude an on-site network including field devices, and a cloud server. In this setup, the BACnet devices may be required to have a distinct connection to the cloud server, for data up^¬ load and download, using the BACnet protocol. For this, the BACnet devices need at least two ports, i.e. one for the on- site interaction and another for connecting to the cloud server. Normally, BACnet devices having more than one port are referred to as BACnet router and are expected to provide message routing between on-site devices and the cloud server via the ports.

FIG. 1 illustrates a graphical representation 100 of the com^¬ munication mechanism in a BACnet router, according to the state of the art. The BACnet router includes a processor, a first port 102 and a second port 104. The first port 102 and the second port 104 are connected to devices in a first net^¬ work and a second network (not shown in the FIG 1) . The BAC^¬ net router communicates with the BACnet protocol, which in^¬ cludes a network layer 106 and an application layer 108. The BACnet router also includes a BACnet application 110 in addi^¬ tion to the application layer 108.

As shown in FIG 1, a message 112a received on the first port 102 is routed to the second port 104 at the network layer 106, as indicated by arrow 112b. For example, the first port 102 has Media Access Control (MAC) address=6 and assigned first network number 40. The second port 104 has MAC ad- dress=7 and assigned second network number 10. The message 112a is a global broadcast message received from a BACnet de- vice with MAC address=8 on the first network connected to the first port 102. The global broadcast message 112a is a type of BACnet Network Protocol Data Unit (NPDU) , whose format in^¬ cludes a header (no source BACnet address SNET/SLEN/SADR) , global broadcast destination DNET=X ' FFFF ' /DLEN=0 /no DADR) and a payload. The global broadcast message 112a is received by port 102 with the data link frame indicating source MAC ad^¬ dress 8 (SA=8), and broadcast destination MAC address (DA=BCAST) . This message is routed to the second port 104 as message 112b and broadcast on the second network. The message 112b is re^¬ ceived by a device on the second network, to which the second port 104 is connected. The message 112b is received with the NPDU header containing ( SNET=40 /SLEN=1 /SADR=8 ) ,

( DNE =X ' FFFF ' /DLEN=0 /no DADR) , and the payload. Further, the data link layer frame conveying the NPDU indicates (SA=7, DA=BCAST) . The message is also routed to the local BACnet ap- plication 110.

Also shown in Figure 1, the arrow 114a indicates a global broadcast message sent by the BACnet application 110. The ar^¬ rows 114a and 114b indicate the global broadcast message sent on the first port 102 and on the second port 104, respective^¬ ly. This routing of messages consumes significant processing resources of the BACnet router.

In a situation where the BACnet protocol is used on a re- source constrained BACnet device, the primary concern is the availability of processing resources. When the BACnet device is connected to multiple BACnet networks by multiple ports, the processor may be overloaded with the routing of messages between multiple ports.

Therefore, in a building automation environment a need exists for providing connectivity with devices in different networks without performing message routing. Further, there exists a need to reduce processing overhead of the BACnet device. Al- so, it is desirable not to route all messages as it may re^¬ veal networks and devices that are hidden or irrelevant.

The method, device and system according to the present inven^¬ tion achieve the aforementioned need by concealing messages received on a first port of a device, from a second port of the device. The device according to the present invention is referred to as a shared device that is capable of communi^¬ cating with devices in different networks and has multiple ports .

The method according to the present invention provides that the shared device is capable of concealing messages by rout^¬ ing a message received on a port of the shared device direct^¬ ly to an application on the shared device, without routing the message to another port of the shared device. Also, the shared device routes a further message sent by the applica^¬ tion to one of the ports of the shared device, based on a destination network number of the further message. Further, the shared device duplicates and routes a global broadcast message sent by the application to each of the ports of the shared device.

As used herein, the following terms are used interchangeably, "first network of devices" and "first network", "second net^¬ work of devices" and "second network", "directly connected BACnet network" and "directly connected network", "indirectly connected BACnet network" and "indirectly connected network", and the "device" and the "shared device".

For the purpose of the present invention, the term "building automation environment" refers to a building automation system that is an integration of controls and services within a building or a setup such as an office building, several buildings in a campus, a plant facility, and the like. The controls and services that are integrated and typically in^¬ clude management of heating, ventilation and air conditioning (HVAC) systems, security systems and services, fire alarm systems, and the like. The integrated and controlled systems are arranged and organized into one or more networks operat^¬ ing according to a common communication scheme and/or network protocol. For example, the typical network protocols include BACnet, KNX, Modbus, LonTalk and the like. Further, the net^¬ work protocols are provided with a cloud link so that they are capable of communicating with a cloud server. Also, the term "BACnet application" refers to an application installed on a BACnet device, such as the shared device. The BACnet ap^¬ plication includes machine readable instructions that are ex^¬ ecuted by a processor in the BACnet device.

According to an embodiment of the present invention, the net^¬ work protocol used to communicate between devices is the Building Automation and Control Network (BACnet, ANSI/ASHRAE Standard 135) protocol. According to the BACnet protocol, the purpose of the network layer is to provide the means by which messages can be relayed from one BACnet network to another. Devices that interconnect two BACnet networks are called BAC- net routers and their activities are called routing. Accord^¬ ingly, the shared device according to the present invention is a BACnet router that not only interconnects the first net^¬ work and a second network, rather connects and communicates with the first network and the second network while conceal- ing them from each other.

Further, according to the BACnet protocol, a message can be a unicast message that is sent from a sending device to a re^¬ ceiving device on another BACnet network (BACnet internet- work) . The message can also be a directed broadcast message, i.e. a message sent from the sending device on the first net^¬ work to all devices on the second network, or a global broad^¬ cast message sent from the sending device on the first net^¬ work to all devices on the BACnet internetwork.

According to the BACnet protocol, the message is represented as a data frame that may include the source network number (SNET) and a source MAC address of the sending device (SLEN/SADR) in an address field of the message. The message is represented as a data frame that may include the destina^¬ tion network number (DNET) and a destination MAC address (DLEN/DADR) for unicast messages, or a respective empty broadcast MAC address (DLEN=0, no DADR) for directed or glob^¬ al broadcasts. Such data frames are referred to as a Network Protocol Data Unit (NPDU) . As used herein, the source network number (SLEN) is the network number assigned to the BACnet network of the sending device. The destination network number (DNET) is the network number assigned to the BACnet network of the receiving device (s) . Network number X ' FFFF ' in DNET is used to indicate a global broadcast. In an embodiment, the source network number is associated with the port on which the message is received by the shared device. The destination network number is associated with the port through which the receiving device can be reached, and through which the mes^¬ sage is to be sent. The source network number (SNET) and the destination network number (DNET) depend on the BACnet network in which the sending device and the receiving device are part of. Both the sending and receiving devices may be pre^¬ sent on an indirectly connected BACnet network. The indirect^¬ ly connected BACnet network is reachable through a BACnet router present in the directly connected network of the first port or the second port, respectively.

In an embodiment of the present invention, the shared device comprises two or more ports including a first port and a sec^¬ ond port connected to directly connected networks or indi^¬ rectly connected networks via the directly connected net- works. The directly connected networks comprise the first network of devices and the second network of devices connect^¬ ed to the first port and the second port, respectively. The indirectly connected networks comprise one or more networks connected to the first network or the second network via one or more BACnet Routers.

According to an embodiment, a unique network number is as^¬ signed to the first network and the first port, and to the second network and the second port. Also, a unique network number is assigned to the indirectly connected networks. When the source network number is not present in the message re^¬ ceived, the unique network number of the port through which the message was received is used as the source network num^¬ ber .

According to another embodiment, the message received by the application on the shared device is read and the destination network number for a response is determined from the source network number of the message.

According to an embodiment, the destination network number is determined based on a configuration of the application. For example, in case of messages initiated by the application, such as event notification messages, the configuration of the application comprises the destination address.

According to another embodiment, the shared device determines the destination address by determining the port of the shared device on which the message is to be sent. The port on which the message is to be sent is the port assigned with the unique network number matching the destination network number. In case of the indirectly connected networks, the port connected to the directly connected network that is in turn connected to the BACnet router and to the indirectly connect^¬ ed network is associated with the unique network number matching the destination network number of the indirectly connected network.

When the destination address is in the directly connected network, the shared device compares the destination network number of the message to the unique network numbers assigned to the first port and the second port. When the destination address is in the indirectly connected network, the shared device compares the destination network number of the message to unique network numbers of the indirectly connected net^¬ works connected to the first network and the second network. Based on the comparison, the shared device encodes a Media Access Control (MAC) address associated with the sending port as the source MAC address.

According to another embodiment, the shared device encodes the MAC address associated with the destination device in the directly connected network, as the destination MAC address.

According to yet another embodiment, the shared device en^¬ codes the MAC address associated with the BACnet router to the indirectly connected network, as the destination MAC ad- dress.

Therefore, according to the present invention, the message is not routed at the network layer to any other port and the message is sent to the BACnet application of the receiving device. This method advantageously conceals the first network and all remote networks behind the first network from the second network and all remote networks behind the second net- work. For example, the shared device can communicate with de^¬ vices on a cloud server through the first network, as well as with devices of the on-site building automation environment through the second network by not revealing the presence of either to devices connected to the other network and all in- directly connected networks behind. Additionally, this method is advantageous as the shared device is capable of fully par^¬ ticipating in multiple BACnet inter-networks (i.e. the first network and the second network) as if the shared device is part of each of the first and second network.

The above-mentioned and other features of the invention will now be addressed with reference to the accompanying drawings of the present invention. The illustrated embodiments are in^¬ tended to illustrate, but not to limit the invention.

The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompany^¬ ing drawings, in which:

FIG 1 illustrates a schematic representation of a commu^¬ nication mechanism in a BACnet router, according state of the art;

FIG 2 illustrates a schematic representation of a shared device according to the present invention;

FIG 3 illustrates a schematic representation of a commu^¬ nication mechanism of the shared device according to the present invention; and FIG 4 is a flowchart illustrating a method for a shared device for communicating with devices in different networks in a building automation environment. Various embodiments are described with reference to the draw^¬ ings, wherein like reference numerals are used to refer to like elements throughout. In the following description, de^¬ vices operating with the BACnet protocol have been considered as an example for the purpose of explanation. These examples must not be considered to limit the application of the inven^¬ tion to a particular communication protocol used in a building automation environment. It may be evident that such em^¬ bodiments may be practiced without these specific details. Further, numerous specific details are set forth in order to provide thorough understanding of one or more embodiments of the present invention.

In the following description, the term "application" refers to a BACnet application installed on a BACnet device, such as the shared device. The application includes machine readable instructions that are executed by a processor in the BACnet device .

FIG 2 illustrates a schematic representation of a shared de- vice according to the present invention. The shared device is connected to the directly connect networks 202, 204 and to the indirectly connected networks 263, 265 via the directly connected networks 202, 204. The directly connected networks 202, 204 are referred to as first network 202 and second net- work 204. As shown in FIG 2, the first network 202 includes one or more devices 202a, 202b. The devices 202a, 202b com^¬ municate according to the BACnet protocol. The second network 204 includes device 204a that is configured to communicate according to the BACnet protocol. Also shown in FIG 2, the indirectly connected networks 263, 265 comprise one or more networks connected to the first network 202 and the second network 204 via BACnet routers 262, 264. The building automation system 200 also includes a device 240 connected to the first network 202 and the second network 204 and is also referred to as the shared device 240. The shared device 240 includes a first port 203 and a second port 205 to communicate with the first network 202 and the second network 204, respectively. In an embodiment, the shared device 240 is configured to communicate according to the BACnet protocol and therefore, includes the layers of the BACnet protocol. As shown in FIG.2, the shared device 240 includes data link lay- ers 206 and 208. In an embodiment, the data link layer 206 is configured as a BACnet/IP or BACnet/MSTP data link. In anoth^¬ er embodiment, the data link layer 208 is configured as a proprietary cloud data link layer port. As shown in FIG. 2, the shared device 240 further includes a network layer 212, an application layer 214 and an application program interface (API) 216. The API 216 is used by ap^¬ plication 218 of the shared device 240. The shared device 240 is capable of participating in the networks 202 and 204 with- out disclosing the existence of the first network 202 to the second network 204, and without disclosing the second network

204 to the first network 202, according the present invention. The shared device 240 achieves the above by routing a message received on either one of ports 203, 205 of the shared device 240 directly to the application 218 on the shared device 240, without routing the message to the other port 205, 203 of the shared device 240. In case of a message sent by the application 218, the shared device routes to one of the ports 203, 205 of the shared device 240, based on a destination network number of the message. Additionally, the shared device 240 duplicates and routes a global broadcast message sent by the application 218 to each of the ports 203,

205 of the shared device 240. This is achieved by configuring the network layer 212 as concealing network layer 212. This is further explained in FIG. 3 and FIG. 4.

FIG. 3 illustrates a schematic representation 300 of a commu^¬ nication mechanism between devices in different networks ac- cording to the present invention. The graphical representa^¬ tion 300 indicates how broadcast messages are routed in the shared device 350. The first port 303 is configured to be part of the first network 302 and the second port 305 is con- figured to be part of the second network 304. In an embodi^¬ ment, the first port 303 receives a message 320 from a send^¬ ing device 302a in the first network 302. The application 310 replies with a global broadcast message 334. The first port 303 sends the reply 314 to the first network 302. The reply 314 is configured such that the source MAC address (SA) of the reply 314 is the MAC address of the first port 303. The second port 305 sends a reply 324 to the second network 304. The reply 324 is configured such that the source MAC address (SA) of the reply 324 is the MAC address of the second port 305. This can be explained with the following example.

In an embodiment, the first port 303 has MAC address=6 and is connected to network 302 with network number 40. The second port 305 has MAC address=7 and is connected to network 304 with network number 10. The message 320 is received from de^¬ vice 302a and is a type of BACnet Network Protocol Data Unit (NPDU) , whose format includes the header (no source BACnet address SNET/SLEN/SADR) , global broadcast destination DNET=X ' FFFF ' /DLEN=0 /no DADR) and the payload. The message 320 has the source MAC addresses 8 (SA=8) and broadcast destina^¬ tion MAC address (DA=BCAST) . As indicated by the arrow, the message 320, the source network number (SNET=40), and the source MAC address ( SLEN/SADR=SA=8 ) is directly forwarded to the application 310 without routing or forwarding to other ports by the network layer 316. The application 310 responds to the message 320 with a global broadcast message 334. The reply 334 must be routed to both the first network 302, and the second network 304. The reply 314 is sent to the first network 302 and the reply 324 is sent to the second network 304. The reply 314 is sent to the first network 302 with NDPU header containing (no SNET/SLEN/SADR) (DNET=X ' FFFF ' /DLEN=0/no DADR) . Further, the data link layer frame conveying the NPDU indicates MAC addresses (SA=6, DA=BCAST) . The source of the reply 314 is indicated as being the first port 303 having the MAC address=6. Further, the reply 324 is sent to the second network 304 with the NPDU header containing (no SNET/SLEN/SADR) ( DNE =X ' FFFF ' /DLEN=0 /no DADR) . Further, the data link layer frame conveying the NPDU indicates MAC ad^¬ dresses (SA=7, DA=BCAST) . The source of the reply 324 is the second port 305 having MAC address=7. Since the second port 305 is configured as part of the second network 304, a re^¬ ceiving device 304a in the second network 304 reads the reply 324 as if it was sent from the second port 305 within the second network 304.

The present invention is advantageous with respect to the routing mechanism known in the art and is elaborated in com- parison with the example in FIG 1. It can be seen that the first network 302 and the second network 304 are able to view only the first port 303 and the second port 305, respective^¬ ly. Accordingly, the devices 302a and 302b in the first net^¬ work 302 are concealed from the device 304a and the second network 304. Further, the MAC address of the shared device 350 is the MAC address of the port 303, 305 used to send the message or reply initiated by the local application.

FIG. 4 is a flowchart illustrating a method 400 of communi- eating between devices in different networks in a building automation system. The building automation system includes a shared device connected to directly connected networks such as a first network and a second network, each having one or more devices. The devices in the first network and the second network are configured to communicate according to the BACnet protocol. Further, the building automation system includes indirectly connected networks comprising one or more networks connected to the first network or the second network via one or more BACnet routers .

At step 402, the method begins by assigning a unique network number to the first network and a first port of the shared device, and to the second network and a second port of the shared device. Further, a unique network number is assigned to indirectly connected networks in the building automation system. At step 404, the first network of the building automation system is assigned a first network number. The first port of the shared device is configured as part of the first network and is therefore assigned the first network number. At step 406, the second network and a second port of the shared device are assigned a second network number.

At step 408, a message is received by the shared device, from a sending device. In an embodiment, the sending device is in the first network and therefore, the message is received on the first port.

At step 410, the message is received by the network layer from the first port.

At step 412, the network layer assigns one of the first net^¬ work number and the second network number as the source net^¬ work number based on whether the message was received from the first network of devices or the second network of devic- es. Considering the example where the sending device is in the first network, the network layer determines that the mes^¬ sage was received from the first network. Accordingly, the source network number (SNET) is the first network number. The source MAC address (SLEN/SADR) is the MAC address of the sending device ( SLEN/SADR=SA) . When the source network number is not present in the message received, the unique network number of the port through which the message was received is used as the source network number. The source MAC address is the MAC address of the sending device in this case.

At step 414, the message is received by the application on the shared device. In an embodiment, the application may re^¬ spond to the sending device on the message and therefore de- termines the destination address for the response from the source address of the message.

At step 416, the application creates a response. The applica- tion determines a destination network number for the response based on the source network number of the received message. In addition, the destination MAC address (DLEN/DADR) for the response is determined from the source MAC address (SLEN/SADR) . At step 416, the destination network number is also determined based on a configuration of the application. The configuration of the application comprises the destina^¬ tion address for messages initiated by the application such as event notification messages. At step 418, the network layer checks the destination network number to determine the port through which the response is to be sent to the original sending device. When the destination network number of the response is the network number of the network connected to first port, or an indirectly connected network behind, step 420 is performed. When the destination network number of the response is the network number of the network connected to the second port, or an indirectly con^¬ nected network behind, step 424 is performed. At step 420, the network layer encodes the response into an NPDU. If the response is to be sent to the indirectly con^¬ nected network behind the network connected to the first port, the destination address of the NPDU (DNET/DLEN/DADR) is the network number and MAC address of the original sending device. If the response is sent to a device connected to the network of the first port, the destination address of the NPDU is absent (no DNET/DLEN/DADR) . The source address of the NPDU (SNET/SLEN/SADR) is omitted in both cases. Step 422 is performed .

At step 424, the network layer encodes the response into an NPDU. If the response is to be sent to a network behind the network connected to the second port, the destination address of the NPDU (DNET/DLEN/DADR) is the network number and MAC address of the original sending device. If the response is sent to a device connected to the network of the second port, the destination address of the NPDU is absent (no DNET/DLEN/DADR) . The source address of the NPDU (SNET/SLEN/SADR) is omitted in both cases. Step 422 is performed .

At step 422, the message is transmitted to the receiving de- vice in the network connected to the port, or to some BACnet router in that network. The source MAC address (SA) of the response is the MAC address of the port through which the message is sent. The destination MAC address (DA) of the re^¬ sponse is the MAC address of the original sending device, or the MAC address of the BACnet router to the indirectly con^¬ nected destination network on which the original sending device resides.

Although components and functions are described that may be implemented in particular embodiments with reference to par^¬ ticular standards and protocols, the components and functions are not limited to such standards and protocols. For example, standards for Internet and other packet switched network transmission (e.g., Transmission Control Protocol/Internet Protocol (TCP/IP), User Datagram Protocol/ Internet Protocol (UDP/IP) , or Hypertext Transfer Protocol (HTTP) represent ex^¬ amples of the state of the art. Such standards are periodi^¬ cally superseded by faster or more efficient equivalents hav^¬ ing essentially the same functions. Accordingly, replacement standards and protocols having the same or similar functions as those disclosed herein are considered equivalents thereof.

The illustrations described herein are intended to provide a general understanding of the structure of various embodi- ments . The illustrations are not intended to serve as a com^¬ plete description of all of the elements and features of ap^¬ paratus, processors, and systems that utilize the structures or methods described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the dis^¬ closure. Other embodiments may be utilized and derived from the disclosure, such that structural and logical substitu^¬ tions and changes may be made without departing from the scope of the disclosure. Additionally, the illustrations are merely representational and may not be drawn to scale. Cer^¬ tain proportions within the illustrations may be exaggerated, while other proportions may be substantially minimized. Ac^¬ cordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive.

Although specific embodiments have been illustrated and de^¬ scribed herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adap^¬ tations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, may be apparent to those of skill in the art upon reviewing the description.

The Abstract is provided with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclo^¬ sure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more fea^¬ tures than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the dis^¬ closed embodiments. Thus, the following claims are incorpo^¬ rated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter. FIG 1

communication mechanism in a BACnet router 100 first port 102

second port 104

network layer 106

application layer 108

BACnet application 110

message 112a

arrow 112b

FIG 2

building automation system 200

directly connect networks 202, 204

first network devices 202a, 202b

second network devices 202a, 202b

first network 202

first port 203

second network 204

second port 205

data link layers 206 and 208

network layer 212

application layer 214

application program interface (API) 216 shared device 240

BACnet routers 262, 264

indirectly connected networks 263, 265

FIG 3

communication mechanism 300

shared device 350

first network 302

first port 303

second network 304

second port 305

message 320

sending device 302A

application 310

global broadcast message 334 reply 314 reply 324

message 320

application 310 network layer 316 receiving device 304a devices 302a and 302b

Claims

1. A method of communicating with devices in different net^¬ works in a building automation system (200), the building au- tomation system (200) comprising a first network of devices (202) and a second network of devices (204), and a shared de^¬ vice (240) connected to both the first network and the second network, the method comprising:

routing a message received on a port of the shared de- vice (240) directly to an application (218) on the shared de^¬ vice (240), without routing the message to another port of the shared device (240);

routing a further message sent by the application (218) to one of the ports of the shared device (240), based on a destination network number of the further message; and

duplicating and routing a global broadcast message sent by the application (218) to each of the ports of the shared device (240) .

2. The method according to claim 1, wherein the shared device (240) comprises two or more ports including a first port and a second port connected to directly connected networks (202, 204) or indirectly connected networks (263, 265) via the di^¬ rectly connected networks; wherein the directly connected networks comprise the first network of devices (202) and the second network of devices (204) connected to the first port and the second port, respectively; and wherein the indirectly connected networks (263, 265) comprise one or more networks connected to the first network or the second network via one or more routers (262, 264) .

3. The method according to claim 2, further comprising:

assigning a unique network number to the first network (202) and the first port, and to the second network (204) and the second port.

assigning a unique network number to the indirectly connected networks (263, 265).

4. The method according to claim 2, further comprising:

using the unique network number of the port through which the message was received as a source network number, when the source network number is not present in the message received .

5. The method according to claim 2, further comprising:

determining a destination address of the message to be sent.

6. The method according to claim 5, wherein determining a destination address of the message to be sent, comprises: reading the message received by the application (218) on the shared device (240); and

determining the destination network number from the source network number of the message received.

7. The method according to claim 5, wherein determining a destination address of the message to be sent, comprises: determining the destination network number based on a configuration of the application (218); wherein the configuration of the application (218) comprises the destination address for messages initiated by the application comprising event notification messages.

8. The method according to one of the claims 6 or 7, further comprises :

determining the send port and sending the message from the application (218) to the network of the send port.

9. The method according to claim 5, wherein determining a destination address of the message to be sent, comprises: determining the port of the shared device (240) on which the message is to be sent, wherein the port on which the mes^¬ sage is to be sent is the port assigned with the unique net^¬ work number matching the destination network number, or the port connected to the directly connected network that is con- nected to the BACnet router and to the indirectly connected network which is assigned with the unique network number matching the destination network number;

comparing the destination network number of the message to the unique network number assigned to the first port and the second port, when the destination address is in the di^¬ rectly connected network;

comparing the destination network number of the message to unique network numbers of the indirectly connected net- works connected to the first network and the second network, when the destination address is in the indirectly connected network; and

encoding a Media Access Control (MAC) address associated with the sending port as the source MAC address.

10. The method according to claim 9, further comprising:

encoding the MAC address associated with the destination device, in the directly connected network, as a destination MAC address.

11. The method according to claim 9, further comprising:

encoding the MAC address associated with the BACnet router to the indirectly connected network connected to the directly connected network, as destination MAC address.

12. A shared device (240) configured to perform the method of one of the claims 1 to 11.

13. The shared device (240) according to claim 12, wherein the shared device is a field device in an on-site building automation system (200) and is communicatively coupled to a cloud server.

14. The shared device (240) according to claim 12, wherein the building automation system (200) comprises two or more networks including a first network of devices (202) and a second network of devices (204), wherein the shared device (240) is connected to both networks, wherein the first net- work (202) of devices (202A, 202B) is a network of field devices in an on-site building automation system (200), and the second network (204) of devices (204A) is a network of devic^¬ es located on a cloud server.

15. A system for communicating between devices in different networks in a building automation environment comprising: a first network of devices (202);

a second network of devices (204); and

a shared device (240) according to one of the claims 12 to 14.