[jira] [Created] (PLC4X-341) PLC4J GIP/CIP Read STRING tag returns null w/error

["Andy Grebe (Jira)" <ji...@apache.org>]

Andy Grebe created PLC4X-341:
--------------------------------

             Summary: PLC4J GIP/CIP Read STRING tag returns null w/error
                 Key: PLC4X-341
                 URL: https://issues.apache.org/jira/browse/PLC4X-341
             Project: Apache PLC4X
          Issue Type: Bug
          Components: Driver-Ethernet/IP, PLC4J
    Affects Versions: 0.9.1
            Reporter: Andy Grebe
         Attachments: eipcipstringread.pcapng

STRING tag reads in plc4j using eip are not returning the string.  The error returned is:

java.lang.NullPointerException: Cannot invoke "org.apache.plc4x.java.api.value.PlcValue.getString()" because the return value of "org.apache.plc4x.java.api.messages.PlcReadResponse.getPlcValue(String)" is null

It looks like plc4j is considering it a structure or array.  If I read with 
{code:java}
%MyString[{index}]:STRING:1 {code}
I can get the individual characters in the string by placing the actual index in \{index}.  So it knows where to start reading the data from. 

When running a wireshark cap, I can see the returned string in the response from the PLC.  Attached is a pcap of the transaction.

 

Code Snippet:
{code:java}
try (PlcConnection plcConnection = new PlcDriverManager().getConnection("eip://127.0.0.1")) {    if (!plcConnection.getMetadata().canRead()) {
        logger.error("PLC connection doesn't support reading.");
        return;
    }    logger.info("PLC connector connected");    // Create a new read request:
    PlcReadRequest.Builder builder = plcConnection.readRequestBuilder();
    logger.info("Created Builder");    builder.addItem("value-1", "%MyString:STRING:1");    PlcReadRequest readRequest = builder.build();    // Register a callback executed as soon as a response arrives.
    logger.info("Make sync request for PLC data");
    PlcReadResponse readResponse = readRequest.execute().get(5000, TimeUnit.MILLISECONDS);
    if (readResponse != null) {
        printPlcResponse(readResponse);
    } else {
        logger.error("An error reading PLC, response is NULL");
    }
    for (String field : readResponse.getFieldNames()){
        rtnArray.add(new PlcReadResponseData(field,
            readResponse.getPlcValue(field).getString()) );  // Exception is thrown here
    }
} catch (PlcConnectionException e) {
    e.printStackTrace();    
} {code}
 



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