Listen only communication mode

In Listen Only (or "Eavesdropping") communication mode, the host interprets data, but neither exerts control nor polls for data.

This mode is often used when one AVEVA Enterprise SCADA system is being replaced by another. Rather than sending queries of its own, the protocol listens to both halves of a protocol conversation between another controlling AVEVA Enterprise SCADA host and the Remote Terminal Unit (RTU). The protocol processes the incoming data as if it had sent the queries itself. This mode is useful for verifying new system accuracy.

As in Host Poll mode, Software Analyzer (SWANA) sessions in Listen Only mode mark queries with a "Q" and responses with an "R".

While in Listen Only mode, the driver stores all received RealTime data in the appropriate RealTime database (RTDB) table (analog, status, rate, or multistate).

Notes: Listen Only mode does not support the collection or storage of Historical data.

The driver does not transmit any data to the field devices while in Listen Only mode.

For Listen Only to function correctly, the Transmission Control Protocol (TCP) socket to which Omnicomm connects must present a stream of correctly ordered query and response messages between the live AVEVA Enterprise SCADA host and field device. Installing and configuring the necessary technology to enable tapping into a Listen Only data stream is a project-specific integration activity. This Listen Only solution only assumes that it will connect to a TCP socket, and start receiving the Listen Only bytes. Previously, this was done using special hardware (serial Listen Only cards), software (Y connector programs or network sniffers), etc. Projects should consult Solution Architects or Senior Project Technical Leads for guidance on establishing Listen Only communications on customer systems.

Listen Only communication mode is a separately licensed protocol function for the following drivers:

• CIP Protocol Driver for OASyS RealTime

• Allen-Bradley DF1 Protocol Driver for OASyS

• Bristol Standard Asynchronous Protocol (BSAP) Legacy Driver for OASyS

• Bristol Standard Asynchronous Protocol (BSAP) Driver with Configurable Gas Load (CGL) for OASyS

• Distributed Network Protocol (DNP3) Driver for OASyS

• Fisher Remote Operations Controller (ROC)/Fisher Remote Operations Controller (ROC) Plus Driver with Configurable Gas Load (CGL) for OASyS

• Extended Modbus (Xmodbus) Protocol Driver for OASyS