Unable to use

[Paulo Roberto Balbino]

I tried the example code (master) against a Modicon PLC, on latest master "whenCompleteAsync" call of the "sendAndReceive" method is never completed. On wireshark I can see the TCP 3-way handshake completed successfully but no request at all.

I also tried version v1.1.1, on this one on wireshark TCP handshake ok, on this version I also can see request and response. But the "whenCompleteAsync" is never called.

[Kevin Herron]

Can you post the full code you are using? It sounds like you might just be letting the program exit.

[Paulo Roberto Balbino]

Same code you provided MasterExample.java, the only difference is that I ported it to Kotlin (Intelij /Windows) and changed the number of masters to 1.

MasterExample(1, 100).start()

Also I added a delay between requests

   for (j in 0 until nRequests) {
                Thread.sleep(1000);
                sendAndReceive(master)
       }

On wireshark, each second I see the modbus request and response. But I dont see the message from println

 future.whenCompleteAsync({ response: ReadHoldingRegistersResponse?, ex: Throwable ->
            if (response != null) {
                println("response")
                println("Response: " + ByteBufUtil.hexDump(response.registers));
                ReferenceCountUtil.release(response)
            } else {
                println("Completed exceptionally, message=${ex.message}")
            }
            scheduler.schedule({ sendAndReceive(master) }, 1, TimeUnit.SECONDS)
        }, Modbus.sharedExecutor())

This is the output I get. I also added two more metrics requestCounter and responseCounter to try to understand what's going on.

Running with v1.1.0. Wireshark: connection ok, also can see req and response (as expected)

Mean rate=0.05851407124404467, 1m rate=2.356221287991323E-12
request counter 100
response counter 100
timeout counter 0
Mean rate=0.05834295290433627, 1m rate=2.1678282356471266E-12
request counter 100
response counter 100
timeout counter 0
Mean rate=0.05817300823468216, 1m rate=1.994498260082879E-12
request counter 100
response counter 100
timeout counter 0
Mean rate=0.05800398511124546, 1m rate=1.8350269841771565E-12
request counter 100
response counter 100
timeout counter 0
Mean rate=0.057836042249378314, 1m rate=1.6883063274862844E-12
request counter 100
response counter 100
timeout counter 0
Mean rate=0.057668622049167804, 1m rate=1.553316806787101E-12

Running with v1.2.0. - Wireshark: connection ok, no request, no response

request counter 0
response counter 0
timeout counter 0
Mean rate=0.0, 1m rate=0.0
request counter 0
response counter 0
timeout counter 0
Mean rate=0.0, 1m rate=0.0
request counter 0
response counter 0
timeout counter 0
Mean rate=0.0, 1m rate=0.0
request counter 0
response counter 0
timeout counter 0
Mean rate=0.0, 1m rate=0.0
request counter 0
response counter 0
timeout counter 0
Mean rate=0.0, 1m rate=0.0

[Kevin Herron]

Have you tried something simple like in the README?

The examples work fine for me, both with the simulated slave and a real PLC, though I had to reduce the concurrent requests down to not overload the PLC.

Try this:

ModbusTcpMasterConfig config = new ModbusTcpMasterConfig.Builder("localhost").build();
ModbusTcpMaster master = new ModbusTcpMaster(config);

master.connect();

CompletableFuture<ReadHoldingRegistersResponse> future =
    master.sendRequest(new ReadHoldingRegistersRequest(0, 10), 0);

future.thenAccept(response -> {
    System.out.println("Response: " + ByteBufUtil.hexDump(response.getRegisters()));

    ReferenceCountUtil.release(response);
});

Thread.sleep(Integer.MAX_VALUE);

Otherwise you'll have to provide me with a fully self-contained and runnable example, not a partial snippet.