[Bug]: PLC4X does not wait for response when reading data from Beckhoff Twincat 3 PLC with Ethernet/IP

[JoonasC]

What happened?

It seems like PLC4X does not wait for a response from the Ethernet/IP server when reading data (specifically using the Ethernet/IP scanner device in Beckhoff Twincat3 PLCs)

I'm using the following code to test reading:

public class Main {
  public static void main(String[] args) {
    String connectionString = "eip://10.50.100.216:44818?bigEndian=false";

    try (PlcConnection plcConnection = PlcDriverManager.getDefault().getConnectionManager().getConnection(connectionString)) {
      PlcReadRequest.Builder readBuilder = plcConnection.readRequestBuilder();
      readBuilder.addTagAddress("Var1", "%Var1");
      PlcReadRequest readRequest = readBuilder.build();
      System.out.println("--- Reading data ---");
      PlcReadResponse readResponse = readRequest.execute().get();
      System.out.println("--- Read complete ---");
      System.out.println(readResponse.getResponseCode("Var1"));
      System.out.println(readResponse.getObject("Var1"));
    } catch (Exception e) {
      System.out.println("Connection failed");
      e.printStackTrace();
    }
  }
}

Stacktrace:

org.apache.plc4x.java.api.exceptions.PlcInvalidTagException: Var1 invalid at org.apache.plc4x.java.spi.messages.DefaultPlcReadResponse.getResponseCode(DefaultPlcReadResponse.java:100) at org.example.Main.main(Main.java:20)

Looking at Wireshark, PLC4X closes the connection before the PLC has a chance to respond to the read request:

Capture.pcapng.gz

I can workaround this bug by adding a manual Thread.sleep before trying to interact with the read response object:

System.out.println("--- Reading data ---");
PlcReadResponse readResponse = readRequest.execute().get();
Thread.sleep(1000);
System.out.println("--- Read complete ---");

Here is my Twincat3 Ethernet/IP explicit messaging configuration:

Version

0.12.0

Programming Languages

• [X] plc4j
• [ ] plc4go
• [ ] plc4c
• [ ] plc4net

Protocols

• [ ] AB-Ethernet
• [ ] ADS /AMS
• [ ] BACnet/IP
• [ ] CANopen
• [ ] DeltaV
• [ ] DF1
• [X] EtherNet/IP
• [ ] Firmata
• [ ] KNXnet/IP
• [ ] Modbus
• [ ] OPC-UA
• [ ] S7

[chrisdutz]

Just a quick question ... why would you access a Beckhoff ADS device with EIP and not ADS? It's sort of like having a Porsche in the garage but driving with the Dacia ;-)

[JoonasC]

I'm investigating the Ethernet/IP functionality of PLC4X, but do not have any other Ethernet/IP capable devices on hand.

[chrisdutz]

Hehe ... ok ... I guess that's really the only case it would make sense ;-)

As I also have a Beckhoff ADS device here ... if you could describe and document how to setup the EIP stuff, I could give it a try on my device.

[JoonasC]

Sure, here is Beckhoff's official documentation: https://infosys.beckhoff.com/english.php?content=../content/1033/tf6281_tc3_ethernetipscanner/index.html&id=

For a TLDR version:

1. Add an Ethernet/IP scanner device:
2. Create a sync task for the device:
3. Create a global variable list called ETHIP, which contains variables declared in the M memory area:
4. Add the Tc2_EthernetIP library to the PLC project:
5. Check the read and write options for tags you want to read/write to:
6. Get the IP address of the Ethernet/IP server from the settings tab: