How to set unitId when i use modbus-tcp-slave

[zhangchunguang1]

var serverTransport = NettyTcpServerTransport.create(cfg -> {
cfg.bindAddress = "localhost";
cfg.port = 50200;
});

[kevinherron]

The unit id isn't selected by the transport. Your implementation of ModbusServices methods will receive the unit id and decide if it's supported.

Optionally, you can use ReadOnlyModbusServices or ReadWriteModbusServices, which have a method you can override to return a ProcessImage for a given unit id:

  protected abstract Optional<ProcessImage> getProcessImage(int unitId);

For example, this would use the same ProcessImage for any unit id provided by the client:

    var processImage = new ProcessImage();

    var modbusServices =
        new ReadWriteModbusServices() {
          @Override
          protected Optional<ProcessImage> getProcessImage(int unitId) {
            return Optional.of(processImage);
          }
        };

and this would support only unit id 1 and 2, the rest being unsupported:

    var processImage = new ProcessImage();

    var modbusServices =
        new ReadWriteModbusServices() {
          @Override
          protected Optional<ProcessImage> getProcessImage(int unitId) {
            return switch (unitId) {
              case 1, 2 -> Optional.of(processImage);
              default -> Optional.empty();
            };
          }
        };

Which approach is more appropriate depends what you are trying to build. The ProcessImage approach is good if your data is in memory. If you're trying to implement e.g. a gateway, then you probably need to just implement ModbusServices directly.

[zhangchunguang1]

Thanks. So, how can I listen to the data received by the server,I want get the data.for example listen the writeCoils,
public void writeCoils(Consumer<Map<Integer, Boolean>> write) {
if (state.get() != State.OPEN) {
throw new IllegalStateException("transaction closed");
}

  var modifications = new ArrayList<CoilModification>();

  coilLock.writeLock().lock();
  try {
    write.accept(
        new TransactionScopedMap<>(coilMap, state) {
          @Override
          protected void recordPut(Integer key, Boolean value) {
            modifications.add(new CoilModification(key, value));
          }

          @Override
          protected void recordRemove(Object key) {
            if (key instanceof Integer k) {
              modifications.add(new CoilModification(k, false));
            }
          }
        });

    notifyCoilsModified(modifications);
  } finally {
    coilLock.writeLock().unlock();
  }
}

[kevinherron]

You can listen for modifications to the ProcessImage like this:

      processImage.addModificationListener(new ModificationListener() {
        @Override
        public void onCoilsModified(List<CoilModification> modifications) {
          // do something with the modifications
          modifications.forEach(System.out::println);
        }
        
        // ... onDiscreteInputsModified, onHoldingRegistersModified, onInputRegistersModified
      });

[zhangchunguang1]

thanks