StreamTransport null pointer exception

[kelden]

I have been trying to implement a RTU slave application, I used the ListenerTest as a start with the necessary modifications to make it create a RTU slave instead of the TCP slave. However when I try to run it I get a NullPointerException at the SteamTransporter.

run:
Stable Library
=========================================
Native lib Version = RXTX-2.1-7
Java lib Version   = RXTX-2.1-7
com.serotonin.modbus4j.exception.ModbusInitException: java.lang.NullPointerException
        at com.serotonin.modbus4j.serial.SerialSlave.start(SerialSlave.java:51)
        at com.serotonin.modbus4j.serial.rtu.RtuSlave.start(RtuSlave.java:40)
        at kiwi.main$1.run(main.java:46)
        at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.NullPointerException
        at com.serotonin.messaging.StreamTransport.start(StreamTransport.java:32)
        at com.serotonin.modbus4j.serial.SerialSlave.start(SerialSlave.java:48)
        ... 3 more

I looked through the examples but couldn't find any that were very relevant except the listener one. Google didn't really turn up anything useful either. When I looked closer at the code I figured it might be something up with the name being passed to StreamTransport and fetched the thread and got it's name and passed that as a variable instead. That didn't make any difference though.

Thanks in advance, hope I didn't miss anything painfully obvious :)

[mlohbihler]

There is a line in SerialSlave that should be removed.

        try {
            serialPort = SerialUtils.openSerialPort(serialParameters);
            transport = new StreamTransport(serialPort.getInputStream(), serialPort.getOutputStream());
            transport.start("Modbus4J SerialSlave");  // &lt&lt&lt REMOVE THIS LINE
        }

The start method should be (and is) called in subclasses. I'm pretty sure this will fix the problem, but i don't have any equipment available to test on. Please let me know if it helps.

[v8dave]

I've just come across this error from 2011 and I only downloaded the code a few days ago.

Why was this error still present in the code?

Anyway, the fix sorted the issue and I now have a working RTU slave.

[statisticblogs]

I looked through the examples but couldn't find any that were very relevant except the listener one. Google didn't really turn up anything useful either. When I looked closer at the code I figured it might be something up with the name being passed to StreamTransport and fetched the thread and got it's name and passed that as a variable instead. That didn't make any difference though.

[mlohbihler]

The line is not in the CVS code. Perhaps it still is in the src jar file. Try using the repo source instead.