Question

i’m trying to read and write on a char device in ubuntu but when i create the outputstream i get this exception:

java.io.FileNotFoundException: /dev/usb/legousbtower0 (Device or resource busy)

This is my code:

myInputStream = new FileInputStream("/dev/usb/legousbtower0");
myOutputStream = new FileOutputStream("/dev/usb/legousbtower0");

The inputstream works and i can write to the device using the terminal

echo test > /dev/usb/legousbtower0

I try to detect what is using the device using fuser but nothing results.

Answer 1

When you open the device as an InputStream, it is marked as open by the operating system. Since only one program should access the device at a time, the second open will fail. You need to open the device in read-write mode, probably using the
RandomAccessFile.