Control Network Newsletter

ARCshark Makes Wireshark Compatible with BACnet ARCNET

October 2011 - Recently, H. Michael Newman at Cornell University contacted Contemporary Controls to help him with an ARCNET issue he was having with their BACnet building automation network. We were the obvious choice because we support both BACnet and ARCNET. His Automated Logic Corporation (ALC) WebCTRL system has LAN Gateway Routers (LGRs) attached to the BACnet/IP Ethernet backbone. On the other side of the LGR is an ARC-156 network that supports BACnet ARCNET at 156kbps. If the ARC-156 network needs to be extended beyond its limits, an ARCNET-ARCNET Router (AAR) is used. Mike's problem was understanding why stations located downstream of an AAR would not respond to BACnet Who-Is messages generated by devices upstream of the AAR.

ALC has a tool that allows you to connect Wireshark to a pass-through port on the LGR so that you can view BACnet ARCNET traffic coming from the connected ARC-156 segment. However, any traffic downstream of an AAR is not viewable. Mike wanted a Wireshark solution that could examine the ARCNET traffic by attaching to "the wires" of the ARC-156 segments downstream of an AAR. He also wanted a convenient tool for his technicians consisting of a laptop computer, our USB22-485 ARCNET adapter and Wireshark.

Wireshark is a very popular open-source protocol analyzer that works with BACnet. Although it is mainly used with Ethernet networks, ARCNET networks are supported but with some degree of effort. The trick for us was to develop a program called ARCshark, which captures all ARCNET messages and saves them in a file format compatible with Wireshark. This allows Wireshark the ability to decode the BACnet ARCNET messages.

"ARCNET systems remain popular, and ARCNET is one of the approved data links in the BACnet standard, so it's not uncommon to see ARCNET and BACnet together," said Bennet Levine, R&D manager at Contemporary Controls. "Developing ARCshark is part of our continuing commitment to support ARCNET installations while helping out a customer."

Because ARCshark uses Contemporary Control's ArcX.dll to communicate with the company's ARCNET cards, ARCshark can work with most Contemporary Controls ARCNET products, such as the PCI20U line of PCI Bus ARCNET adapters, the USB22 line of USB ARCNET adapters and the AI-SRVR line of ARCNET to Ethernet servers. With ARCshark and a USB22-485, Mike was able to solve his problem.

Visit the ARCshark homepage to download ARCshark.