[PLC4X-311] ADS driver lost with short replies for read requests

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: 0.9.0
• Component/s: Driver-ADS
• Labels: regresion

Language

Java

• Assignee: Łukasz Dywicki
• Reporter: Łukasz Dywicki
• Created: 25/Aug/21 08:55
• Updated: 16/Sep/21 15:51
• Resolved: 16/Sep/21 15:51

Description

I began testing functionality which did work with ADS driver in 0.6 release. Part of the test was reading address 0xf00f/0x0 (it is elsewhere referred as SYM_UPLOADINFO2) which returns up to 24 bytes of data. First 4 is symbol count, next 4 is symbol list length. Not sure what are remaining ones.
I made an attempt to read less than 24 bytes. All requests which query below 24 bytes get response which do not contain index group and offset.
I attach PCAP which clearly indicates issue.

Actual code:

PlcConnection = new PlcDriverManager().getConnection("ads:tcp://...");
ReadRequestBuilder readRequestBuilder = plcConnection.readRequestBuilder();
PlcReadRequest request = readRequestBuilder
     // change array size to 23 to face the issue
    .addItem("symbol", "0xf00f/0x0:BYTE[24]").build();
PlcReadResponse rsp = request.execute().whenComplete((r, e) -> {
    if (e != null) {
        e.printStackTrace();
    } else {
        dump(r);
    }
}).get();

TwinCAT: 2.11 (build 2286)
Hardware: CX 9000-0001

Tested with TwinCT: 3.1.4024.0 simulator and I get similar results when requesting data from 0xf00f register. For TC3 actual behavior is the same.

Issue Links

• links to: GitHub Pull Request #268