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Posted to issues@plc4x.apache.org by "IsmoLeszczynski (via GitHub)" <gi...@apache.org> on 2025/04/08 18:13:01 UTC
[I] [Bug]: Modbus: Reading single discrete-input throws ArrayIndexOutOfBoundsException
IsmoLeszczynski opened a new issue, #2054:
URL: https://github.com/apache/plc4x/issues/2054
### What happened?
I'm trying out the Modbus driver with a simulator and things were going well while reading, for example, INT from holding registers, but when I tried to read a single BOOL from discrete inputs, the ModbusOptimizer throws an exception when handling the response. With a quick glance at the decompiled sources, I'm guessing this happens because BOOL is defined with a dataTypeLength of 2:
`public enum ModbusDataType {
BOOL((short)1, (short)2),
...
}`
Is this correct? I'd expect BOOL to be defined with a length of 1, but I'm not sure if there is some technical reason for this deeper down.
The tag address I tested: `discrete-input:1:BOOL`
`2025-04-08 20:52:05,056 ERROR [nioEventLoopGroup-3-1] org.apache.plc4x.java.modbus.base.optimizer.ModbusOptimizer - Error processing response:
java.lang.ArrayIndexOutOfBoundsException: arraycopy: last source index 2 out of bounds for byte[1]
at java.base/java.lang.System.arraycopy(Native Method)
at org.apache.plc4x.java.modbus.base.optimizer.ModbusOptimizer$Response.getResponseDataForTag(ModbusOptimizer.java:410)
at org.apache.plc4x.java.modbus.base.optimizer.ModbusOptimizer.processReadResponses(ModbusOptimizer.java:232)
at org.apache.plc4x.java.spi.optimizer.BaseOptimizer.lambda$1(BaseOptimizer.java:112)
at org.apache.plc4x.java.spi.optimizer.BaseOptimizer.lambda$8(BaseOptimizer.java:205)
at java.base/java.util.concurrent.CompletableFuture.uniHandle(CompletableFuture.java:934)
at java.base/java.util.concurrent.CompletableFuture$UniHandle.tryFire(CompletableFuture.java:911)
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510)
at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2179)
at org.apache.plc4x.java.modbus.tcp.protocol.ModbusTcpProtocolLogic.lambda$11(ModbusTcpProtocolLogic.java:163)
at java.base/java.util.function.Consumer.lambda$andThen$0(Consumer.java:65)
at org.apache.plc4x.java.spi.Plc4xNettyWrapper.decode(Plc4xNettyWrapper.java:194)
at io.netty.handler.codec.MessageToMessageCodec$2.decode(MessageToMessageCodec.java:81)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:88)
at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318)
at io.netty.handler.codec.ByteToMessageCodec.channelRead(ByteToMessageCodec.java:103)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1407)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:918)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:994)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.base/java.lang.Thread.run(Thread.java:1583)
2025-04-08 20:52:05,068 ERROR [nioEventLoopGroup-3-1] org.apache.plc4x.java.modbus.base.optimizer.ModbusOptimizer - Original Request:
<PlcReadRequest>
<PlcTagRequest>
<tags isList="true">
<ModbusTagDiscreteInput {address=0, quantity=1, dataType=BOOL, unitId=null }>
<PlcTagItem>
<tag>
<ModbusTagDiscreteInput>
<address dataType="uint" bitLength="16">0</address>
<numberOfElements dataType="uint" bitLength="16">1</numberOfElements>
<dataType dataType="string" bitLength="32" encoding="UTF-8">BOOL</dataType>
</ModbusTagDiscreteInput>
</tag>
</PlcTagItem>
</ModbusTagDiscreteInput {address=0, quantity=1, dataType=BOOL, unitId=null }>
</tags>
</PlcTagRequest>
</PlcReadRequest>
java.lang.ArrayIndexOutOfBoundsException: arraycopy: last source index 2 out of bounds for byte[1]
at java.base/java.lang.System.arraycopy(Native Method)
at org.apache.plc4x.java.modbus.base.optimizer.ModbusOptimizer$Response.getResponseDataForTag(ModbusOptimizer.java:410)
at org.apache.plc4x.java.modbus.base.optimizer.ModbusOptimizer.processReadResponses(ModbusOptimizer.java:232)
at org.apache.plc4x.java.spi.optimizer.BaseOptimizer.lambda$1(BaseOptimizer.java:112)
at org.apache.plc4x.java.spi.optimizer.BaseOptimizer.lambda$8(BaseOptimizer.java:205)
at java.base/java.util.concurrent.CompletableFuture.uniHandle(CompletableFuture.java:934)
at java.base/java.util.concurrent.CompletableFuture$UniHandle.tryFire(CompletableFuture.java:911)
at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510)
at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2179)
at org.apache.plc4x.java.modbus.tcp.protocol.ModbusTcpProtocolLogic.lambda$11(ModbusTcpProtocolLogic.java:163)
at java.base/java.util.function.Consumer.lambda$andThen$0(Consumer.java:65)
at org.apache.plc4x.java.spi.Plc4xNettyWrapper.decode(Plc4xNettyWrapper.java:194)
at io.netty.handler.codec.MessageToMessageCodec$2.decode(MessageToMessageCodec.java:81)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:88)
at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
at io.netty.handler.codec.MessageToMessageCodec.channelRead(MessageToMessageCodec.java:111)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318)
at io.netty.handler.codec.ByteToMessageCodec.channelRead(ByteToMessageCodec.java:103)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:442)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1407)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:918)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:994)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.base/java.lang.Thread.run(Thread.java:1583)
2025-04-08 20:52:05,078 ERROR [nioEventLoopGroup-3-1] org.apache.plc4x.java.modbus.base.optimizer.ModbusOptimizer - Sub Request:
<PlcReadRequest>
<PlcTagRequest>
<tags isList="true">
<registers0>
<PlcTagItem>
<tag>
<ModbusTagDiscreteInput>
<address dataType="uint" bitLength="16">0</address>
<numberOfElements dataType="uint" bitLength="16">1</numberOfElements>
<dataType dataType="string" bitLength="32" encoding="UTF-8">WORD</dataType>
</ModbusTagDiscreteInput>
</tag>
</PlcTagItem>
</registers0>
</tags>
</PlcTagRequest>
</PlcReadRequest>
2025-04-08 20:52:05,086 ERROR [nioEventLoopGroup-3-1] org.apache.plc4x.java.modbus.base.optimizer.ModbusOptimizer - Sub Response (Success):
<PlcReadResponse>
<request>
<PlcReadRequest>
<PlcTagRequest>
<tags isList="true">
<registers0>
<PlcTagItem>
<tag>
<ModbusTagDiscreteInput>
<address dataType="uint" bitLength="16">0</address>
<numberOfElements dataType="uint" bitLength="16">1</numberOfElements>
<dataType dataType="string" bitLength="32" encoding="UTF-8">WORD</dataType>
</ModbusTagDiscreteInput>
</tag>
</PlcTagItem>
</registers0>
</tags>
</PlcTagRequest>
</PlcReadRequest>
</request>
<values isList="true">
<registers0>
<PlcResponseItem>
<code dataType="string" bitLength="16" encoding="UTF-8">OK</code>
<value>
<PlcRawByteArray dataType="byte" bitLength="8">0x00</PlcRawByteArray>
</value>
</PlcResponseItem>
</registers0>
</values>
</PlcReadResponse>`
### Version
v0.13.0-SNAPSHOT
### Programming Languages
- [ ] plc4c
- [ ] plc4go
- [x] plc4j
- [ ] plc4net
- [ ] plc4py
### Protocols
- [ ] AB-Ethernet
- [ ] ADS /AMS
- [ ] BACnet/IP
- [ ] C-Bus
- [ ] CANopen
- [ ] EtherNet/IP
- [ ] Firmata
- [ ] IEC-69870
- [ ] KNXnet/IP
- [x] Modbus
- [ ] OPC-UA
- [ ] Profinet
- [ ] S7
- [ ] S7-light
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Re: [I] [Bug]: Modbus: Reading single discrete-input throws ArrayIndexOutOfBoundsException
Posted by "chrisdutz (via GitHub)" <gi...@apache.org>.
chrisdutz commented on issue #2054:
URL: https://github.com/apache/plc4x/issues/2054#issuecomment-2787767043
Discrete inputs are two byte values, right?
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Re: [I] [Bug]: Modbus: Reading single discrete-input throws ArrayIndexOutOfBoundsException
Posted by "IsmoLeszczynski (via GitHub)" <gi...@apache.org>.
IsmoLeszczynski commented on issue #2054:
URL: https://github.com/apache/plc4x/issues/2054#issuecomment-2787873479
Have to admit I'm not too savvy with the specifics, but the Coils and Discrete Inputs are single bits, and if I understand correctly, the result data is the resulting bits padded to the next full byte, `(InputCount + 7) / 8` bytes. In my case, the complete result would then be 3 bytes; the function code byte, the number of inputs byte, and the input data byte - with 1 bit result padded to a full byte.
The Input/Holding Registers are always two bytes per address.
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Re: [I] [Bug]: Modbus: Reading single discrete-input throws ArrayIndexOutOfBoundsException
Posted by "hutcheb (via GitHub)" <gi...@apache.org>.
hutcheb commented on issue #2054:
URL: https://github.com/apache/plc4x/issues/2054#issuecomment-2787909170
Yeah these get packed and padded into bytes, if you request 3 bits you'll receive one byte, 14 bits and you'll get 2 bytes.
As the mspec specifies the number of bytes for a boolean, it doesn't really make sense, booleans (Discrete coils/inputs) are handled with custom logic in each implementation to unpack them.
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Re: [I] [Bug]: Modbus: Reading single discrete-input throws ArrayIndexOutOfBoundsException
Posted by "glcj (via GitHub)" <gi...@apache.org>.
glcj commented on issue #2054:
URL: https://github.com/apache/plc4x/issues/2054#issuecomment-2788223373
Hi,
You can try this branch; I think it solves the problem.
I'll keep an eye out.
https://github.com/apache/plc4x/tree/fix/modbus
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Re: [I] [Bug]: Modbus: Reading single discrete-input throws ArrayIndexOutOfBoundsException
Posted by "IsmoLeszczynski (via GitHub)" <gi...@apache.org>.
IsmoLeszczynski commented on issue #2054:
URL: https://github.com/apache/plc4x/issues/2054#issuecomment-2789389081
As far as I could tell, that solution didn't handle the Discrete Inputs nor Coils, when the response was a single byte - it was still trying to read too many bytes. To me it seems that the only required change is to handle Discrete Inputs just like the Coils, I made a pr for it #2055. This version, at least, worked for me with my modbus simulator (MOD_RSsim).
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Re: [I] [Bug]: Modbus: Reading single discrete-input throws ArrayIndexOutOfBoundsException
Posted by "sruehl (via GitHub)" <gi...@apache.org>.
sruehl closed issue #2054: [Bug]: Modbus: Reading single discrete-input throws ArrayIndexOutOfBoundsException
URL: https://github.com/apache/plc4x/issues/2054
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