- Introduced a new optional "slaveId" parameter to the modbus driver

plc4j/drivers/modbus/src/main/java/org/apache/plc4x/java/modbus/connection/BaseModbusPlcConnection.java

@@ -36,6 +36,9 @@ public abstract class BaseModbusPlcConnection extends NettyPlcConnection impleme
 
     private static final Logger logger = LoggerFactory.getLogger(BaseModbusPlcConnection.class);
 
+    // This slaveId defaults to 0 which is a broadcast.
+    private short slaveId = 0;
+
     BaseModbusPlcConnection(ChannelFactory channelFactory, String params) {
         super(channelFactory);
 
@@ -46,6 +49,9 @@ public abstract class BaseModbusPlcConnection extends NettyPlcConnection impleme
                 if (paramElements.length == 2) {
                     String paramValue = paramElements[1];
                     switch (paramName) {
+                        case "slaveId": {
+                            slaveId = Short.parseShort(paramValue);
+                        }
                         default:
                             logger.debug("Unknown parameter {} with value {}", paramName, paramValue);
                     }
@@ -104,4 +110,8 @@ public CompletableFuture<PlcWriteResponse> write(PlcWriteRequest writeRequest) {
             .thenApply(PlcWriteResponse.class::cast);
     }
 
+    public short getSlaveId() {
+        return slaveId;
+    }
+
 }

plc4j/drivers/modbus/src/main/java/org/apache/plc4x/java/modbus/connection/ModbusTcpPlcConnection.java

@@ -69,7 +69,7 @@ protected ChannelHandler getChannelHandler(CompletableFuture<Void> sessionSetupC
             @Override
             protected void initChannel(Channel channel) {
                 channel.pipeline().addLast(new ModbusTcpCodec(new ModbusRequestEncoder(), new ModbusResponseDecoder()));
-                channel.pipeline().addLast(new Plc4XModbusProtocol());
+                channel.pipeline().addLast(new Plc4XModbusProtocol(getSlaveId()));
                 channel.pipeline().addLast(new SingleItemToSingleRequestProtocol(ModbusTcpPlcConnection.this, ModbusTcpPlcConnection.this, null, timer, null, false));
             }
         };

plc4j/drivers/modbus/src/test/java/org/apache/plc4x/java/modbus/ModbusPlcDriverTest.java

@@ -85,6 +85,15 @@ private void assertMatching(Pattern pattern, String match) {
     public void getConnection() throws Exception {
         ModbusTcpPlcConnection modbusConnection = (ModbusTcpPlcConnection)
             new PlcDriverManager().getConnection("modbus:tcp://localhost:" + tcpHexDumper.getPort());
+        assertThat(modbusConnection.getSlaveId(), is((short) 0));
+        modbusConnection.close();
+    }
+
+    @Test
+    public void getConnectionWithSlaveId() throws Exception {
+        ModbusTcpPlcConnection modbusConnection = (ModbusTcpPlcConnection)
+            new PlcDriverManager().getConnection("modbus:tcp://localhost:" + tcpHexDumper.getPort() + "?slaveId=42");
+        assertThat(modbusConnection.getSlaveId(), is((short) 42));
         modbusConnection.close();
     }
 

plc4j/protocols/modbus/src/main/java/org/apache/plc4x/java/modbus/netty/Plc4XModbusProtocol.java

@@ -60,6 +60,12 @@ public class Plc4XModbusProtocol extends MessageToMessageCodec<ModbusTcpPayload,
 
     private final ConcurrentMap<Short, PlcRequestContainer<InternalPlcRequest, InternalPlcResponse>> requestsMap = new ConcurrentHashMap<>();
 
+    private final short slaveId;
+
+    public Plc4XModbusProtocol(short slaveId) {
+        this.slaveId = slaveId;
+    }
+
     @Override
     protected void encode(ChannelHandlerContext ctx, PlcRequestContainer<InternalPlcRequest, InternalPlcResponse> msg, List<Object> out) throws Exception {
         LOGGER.trace("(<--OUT): {}, {}, {}", ctx, msg, out);
@@ -89,8 +95,6 @@ private void encodeWriteRequest(PlcRequestContainer<InternalPlcRequest, Internal
             LOGGER.warn("Supplied number of values [{}] don't match t the addressed quantity of [{}]", field.getQuantity(), quantity);
         }
 
-        short unitId = 0;
-
         /*
          * It seems that in Modbus, there are only two types of resources, that can be accessed:
          * - Register: 2 byte value
@@ -163,7 +167,7 @@ private void encodeWriteRequest(PlcRequestContainer<InternalPlcRequest, Internal
         }
         short transactionId = (short) this.transactionId.getAndIncrement();
         requestsMap.put(transactionId, msg);
-        out.add(new ModbusTcpPayload(transactionId, unitId, modbusRequest));
+        out.add(new ModbusTcpPayload(transactionId, slaveId, modbusRequest));
     }
 
     private void encodeReadRequest(PlcRequestContainer<InternalPlcRequest, InternalPlcResponse> msg, List<Object> out) throws PlcException {
@@ -178,8 +182,6 @@ private void encodeReadRequest(PlcRequestContainer<InternalPlcRequest, InternalP
 
         ModbusField field = (ModbusField) request.getField(fieldName);
         int quantity = field.getQuantity();
-        // TODO: the unit the should be used for multiple Requests
-        short unitId = 0;
 
         ModbusPdu modbusRequest;
         if (field instanceof CoilModbusField) {
@@ -202,7 +204,7 @@ private void encodeReadRequest(PlcRequestContainer<InternalPlcRequest, InternalP
         }
         short transactionId = (short) this.transactionId.getAndIncrement();
         requestsMap.put(transactionId, msg);
-        out.add(new ModbusTcpPayload(transactionId, unitId, modbusRequest));
+        out.add(new ModbusTcpPayload(transactionId, slaveId, modbusRequest));
     }
 
     @SuppressWarnings("unchecked")
@@ -523,4 +525,4 @@ private DefaultModbusByteArrayFieldItem produceRegisterValueList(ByteBuf byteBuf
         }
         return new DefaultModbusByteArrayFieldItem(data.toArray(new Byte[0][0]));
     }
-}
+}

plc4j/protocols/modbus/src/test/java/org/apache/plc4x/java/modbus/netty/Plc4XModbusProtocolTest.java

@@ -158,7 +158,7 @@ private static byte[] cutRegister(byte[] right) {
 
     @Before
     public void setUp() {
-        SUT = new Plc4XModbusProtocol();
+        SUT = new Plc4XModbusProtocol((short) 1);
     }
 
     @Test