- Application - Heartbeat over TCP/IP (client)

Description:

This script establishes a communication channel to a host device (e.g. PC or PLC) and maintains the communication link via a heartbeat. The heartbeat process is where the DataMan reader sends a defined message (e.g. “HB”) to the host device periodically after fixed intervals. This is implemented using a Communication script, no Data Formatting script is required for the heartbeat function.

Explanation:

First the host device-DataMan communication is captured in the onConnect part of the script. It will handle the connection which is defined by the IP address of the host device and the port it connects on. Using the setTimer feature, it defines a timer. This setTimer feature also takes an argument as an input which is the time interval in seconds that the timer increments up to. When the timer reaches the value specified in the argument, this calls the onTimer function. It then sends the heartbeat message to the host and starts the timer from zero.

How to use the script:

The following parameters are listed at the top of the script and are listed must be set as required for the application:

• HB_IP: IP address of the PC/PLC that receives a heartbeat message from the DataMan
• HB_CLIENT: a Boolean which controls whether the DataMan communicates as a Network Client (when ‘true’) or via Telnet (when ‘false’).
• HB_CLIENT_PORT: the port number used when the DataMan connects via Network Client.
• HB_TELNET_PORT:  the port number used when the DataMan communicates via Telnet.
• HB_TX_HEADER: The defined start char(s) which DataMan prefixes the data string with.
• HB_TX_FOOTER: The defined end char(s) which DataMan closes the data string with.
• HB_TX_MSG: The defined heartbeat message that the DataMan reader responds to the host with.
• HB_TIME: The defined time interval (in seconds) for sending the heartbeat message to the host.

Settings for DataMan:

1. Connect to DataMan reader and navigate to Communications button as shown in Figure 1.
2. In Communication page go to Ethernet Tab.
3. If communication with host is via Network Client then follow these steps:
   1. Set the Host IP address and communication port (mentioned in the script) under Network Client.
   2. Check the Enabled checkbox, save and reboot the device.
4. If communication with host is via Telnet then follow these steps:
   1. Set the communication port under Telnet.
   2. Uncheck the Enabled checkbox under Network Client, save and reboot the device.
5. Now load the Communication script to the reader and ensure parameters match between reader settings and script.

Communication Script:

'use strict';

// Enable/disable logging

const LOG = true;

const HB_IP = '192.168.0.100';   // IP address where to send the heartbeat (could be PLC, PC etc.)

const HB_CLIENT = false;

const HB_CLIENT_PORT = '1000';// Network Client port which DataMan communicates on

const HB_TELNET_PORT = '23';   // Telnet port which DataMan communicates on

const HB_TX_HEADER = '?';         // Define the header for message to host device

const HB_TX_FOOTER = '!';          // Define the footer for message to host device

const HB_TX_MSG = 'HB';            // Define the heartbeat message to send to host device

const HB_TIME = 10;                     // Define the time interval (in seconds) for sending the heartbeat message

let heartbeatHandler = null;

function CommHandler (localName) {

 return {

   onConnect: function (peerName) {

     const sourceIP = peerName.substr(0, peerName.lastIndexOf(':'));

     const peerPort = peerName.substr(peerName.lastIndexOf(':') + 1);

     const localPort = localName.substr(peerName.lastIndexOf(':') + 1);

     // If IP is the defined host IP address and specified port

     if (sourceIP === HB_IP && ((peerPort === HB_CLIENT_PORT && HB_CLIENT) || (localPort === HB_TELNET_PORT && !HB_CLIENT))) {

       heartbeatHandler = this;

       logMsg(HB_IP + ': Connected');

       this.setTimer(HB_TIME);

       return true;

     }

     return false;

   },

   onDisconnect: function () {

     if (this === heartbeatHandler) {

       heartbeatHandler = null;

       logMsg(HB_IP + ': Disconnected');

       return true;

     }

     return false;

   },

   onError: function (errorMsg) {

   },

   onExpectedData: function () {

   },

   onUnexpectedData: function () {

   },

   onTimer: function () {

     if (this === heartbeatHandler) {

       heartbeatHandler.send(HB_TX_HEADER + HB_TX_MSG + HB_TX_FOOTER);

       heartbeatHandler.setTimer(HB_TIME);

     }

              },

   onEncoder: function () {

   }

 };

}

function logMsg (msg) {

 if (LOG) {

   console.log(msg);

 }

}