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

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

    [ https://issues.apache.org/jira/browse/PLC4X-341?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17551226#comment-17551226 ] 

Andy Grebe commented on PLC4X-341:
----------------------------------

I updated to the latest, i.e. followed the procedure to contribute, but the
connect to the AB doesn't work in 0.10.0.  I'll take a look into that.




> 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
>            Priority: Major
>         Attachments: eipcipstringread.pcapng, eipcipstringwrite1.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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