Data Listener

Overview

The Data Listener Communication Sources are passive methods of receiving data. The Data Listener will not poll any device, it will simply listen for data to come in on the associated communication channel. Common uses for Data Listeners will be barcode scanners, RFID scanners, or another application that has the capability of sending unsolicited data. The DataXchange ODI provides Data Listener data as well.

When defining a Data Listener a name must be provided to identify the listener. The name will be used when expressions are assigned to ensure an expression is using the appropriate data listener if multiple have been defined.

There are two different Communication Sources for Data Listeners: Data Listener TCP, and Data Listener Serial. Data can be received from both protocols.

String Control

Many times when data is received the data will arrive in separate portions, such as multiple different scans from a barcode scanner on scanners that are not programmed to buffer the data. By using Append and Termination characters in the strings DataXchange can buffer the data. The Append and Termination characters can be configured when defining the Communication Source.

The Append String is used to buffer incoming data. If the characters at the end of the string received match the Append String then the Append String characters will be stripped and the remaining string will be buffered by DataXchange.

The Termination String is used to process buffered data. If the characters at the end of the string received match the Termination String then the Termination String characters will be stripped and the remaining string will be appended to any buffered data and then the entire string will be processed.

If an Append String is specified then a Termination String must also be specified. A Termination string can be specified without an Append String.

If Append or Termination Strings have been specified and the data received does not contain either the Append or Termination String at the end of the string the received string will be discarded. The logging window can be used to show when data has been buffered or discarded.

Hexadecimal characters can be specified for the Append and Termination Strings by selecting the Use Hex Values check box. The two digit hex value is used to specify each ASCII character.  For example, to use a carriage return and a line feed 0D0A should be entered.