Cannot read data from the /dev/ttyUSB0 with the Java sample for the Magician dobot


Using the Java sample of the DobotDemoV2.0 package for the Magician it crashes always
see my call and the results below:

after debugging with qDebug calls I found the reason, the app couldn’t read any data back from the /dev/ttyUSB0 port where the dobot was connected. Why is the program not able to read any data back, can anybody tell me the reason.

I use ubuntu v18.04 LTS with qt 5.9.5 and Java 1.8.0_45 I also recompiled the DobotDll with release and the debug version it was always the same result

the java call was

$ java -cp lib/jna-4.2.2.jar:bin/:bin/CPlusDll/:jnalib/lib/debug/ Main

the output:

$ sudo chmod 666 /dev/ttyUSB0
$ sudo chown otmar:dialout /dev/ttyUSB0
$ java -cp lib/jna-4.2.2.jar:bin/:bin/CPlusDll/:jnalib/lib/debug/ Main
CDobotConnector : QThread(0x7f3c3c2685c0)
CDobotProtocol : QThread(0x7f3c3c2687b0)
CDobotCommunicator : QThread(0x7f3c3c269960)

A fatal error has been detected by the Java Runtime Environment:

SIGSEGV (0xb) at pc=0x00007f3c1d8b2dd1, pid=25201, tid=139896031696640

JRE version: Java™ SE Runtime Environment (8.0_45-b14) (build 1.8.0_45-b14)

Java VM: Java HotSpot™ 64-Bit Server VM (25.45-b02 mixed mode linux-amd64 compressed oops)

Problematic frame:

C [] CDobotConnector::connectDobot(void*, void*, void*, unsigned int, void*, void*)+0x539

Failed to write core dump. Core dumps have been disabled. To enable core dumping, try “ulimit -c unlimited” before starting Java again

An error report file with more information is saved as:


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Hi Otmar,
could you figure out what the problem was? Same issue here! Tested with MAC and Windows Environment, same situation. Any help is greatly appreciated!


PS. the DLLs seem fine as they work via the Python Demos, must/should relate to the Java environment, am I right?