Make sure you have keyed your host message on the command name data item in the message definition. The script in the matching host message will be run when the host message is received. If you are having trouble with message matching, read the article on Message Matching.

As a quick test of message matching, enter a script which just prints out a simple message when the message is received, for example:

print("Received Host Message START");

This example uses the host command “STOP” as an example of message handling. The STOP command has no parameters for simplicity. The goal is to tell the control application that the STOP has been requested and send an S2F42 reply to the host with a code indicating whether or not the host command is accepted.

Here is how this STOP command is defined in TransSECS:

The highlighted node is the command name parameter with the value “STOP”. This is the “key” for the message matching. This parameter is also “published”. Publishing a parameter in the message allows access to the value using a “get” method. For example to get the value of the incoming command use “getCommand()” on the incoming message.

The "getParameterName()" and "setParameterName(xxx)" methods for a message are case sensitive. If you define your message with a parameter name "command", use getcommand() and not getCommand() to get this value from the incoming message.

print("Received Host Message STOP");
//write a flag to the device so that the control application knows that the STOP was received
/Devices/ModbusTCP_Severs/StopReceived->setIntValue(1);
 
//wait for the control application to reset this flag to "99" 
//we will wait up to 2 seconds (2000 ms), and check every 200 ms
 
//wait up to 2000 ms for the controller to acknowledge the STOP command and set the hcack
 
count=0;
flag=1; //when the flag changes to a different value, controller has finished processing
 
while ((flag==1) && (count<10)) { { //repeat up to 10 times for 2000 ms total
    java.lang.Thread.sleep(200);//wait 200 ms
    count++;
    flag=/Devices/ModbusTCP_Servers/StopReceived->getIntValue(); 
    //if flag is still 1, repeat wait, otherwise exit
 }
 
//get the hcack from the controller. 
 
if (flag!=1) { //controller acknowledged STOP command and calculated the hcack
  hcack=/Devices/ModbusTCP_Servers/StopCommandHCACK->getIntValue();
 } else {
 hcack=99; //controller timeout
}

The next step to handling the host command is to send the host command reply with the HCACK read from the device, or set to “99” if the controller timed out waiting for the message to be processed.

var TransSecsController = Java.type("com.ergotech.transsecs.secs.TransSecsController");
 
secsInterface=TransSecsController.findController("PLCTool"); 
//replace the parameter in findController with the name set for your tool in the TransSECS project
 
reply = secsInterface.getMessageBean("HostCommandReply"); 
//This will use the message defined in TransSECS called "HostMessageReply"
 
reply.setHCACK(Java.to([hcack],"byte[]")); //this sets the HCACK parameter in the HostMessageReply with the hcack read from the device (or "99" if the controller timed out)
 
//send the reply message
 
reply.sendMessage();

As an example, the host command START message in the PLCTool has a single parameter