wborn
commented
4 years ago I've made this example which reproduces the issue. It prints all available ports, opens a port after 2 secs and then prints all available ports every 5 secs.
package example;
import java.util.Enumeration;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import gnu.io.CommPortIdentifier;
public class Main {
private static final Lock LOCK = new ReentrantLock();
private static final String PORT = "/dev/ttyUSB0";
public static void main(String[] args) throws Exception {
Thread thread = new Thread(Main::printPortIdentifiers);
thread.start();
Thread.sleep(2000L);
CommPortIdentifier id = CommPortIdentifier.getPortIdentifier(PORT);
id.open(Main.class.getSimpleName(), 5000);
System.out.println("Opened: " + PORT);
LOCK.lock();
}
@SuppressWarnings("unchecked")
private static void printPortIdentifiers() {
try {
while (!Thread.currentThread().isInterrupted()) {
Enumeration<CommPortIdentifier> ids = CommPortIdentifier.getPortIdentifiers();
System.out.println("--- Port Identifiers ---");
while (ids.hasMoreElements()) {
System.out.println("name: " + ids.nextElement().getName());
}
System.out.println();
Thread.sleep(5000L);
}
} catch (InterruptedException e) {
System.out.println("Thread interrupted");
}
}
}The output is:
--- Port Identifiers ---
name: /dev/ttyUSB0
Opened: /dev/ttyUSB0
RXTX fhs_lock() Error: opening lock file: /var/lock/LCK..ttyUSB0: File exists. It is mine
testRead() Lock file failed
--- Port Identifiers ---
RXTX fhs_lock() Error: opening lock file: /var/lock/LCK..ttyUSB0: File exists. It is mine
testRead() Lock file failed
--- Port Identifiers ---
RXTX fhs_lock() Error: opening lock file: /var/lock/LCK..ttyUSB0: File exists. It is mine
testRead() Lock file failed
--- Port Identifiers ---
RXTX fhs_lock() Error: opening lock file: /var/lock/LCK..ttyUSB0: File exists. It is mine
testRead() Lock file failed
--- Port Identifiers ---
madhephaestus
When using v3.19.0 (and earlier) on Linux x86_64 we see the following errors printed:
It occurs when calling
CommPortIdentifier.getPortIdentifiers()with an open (locked) connection whilegnu.io.rxtx.SerialPortsisn't set so the library registers scanned ports:https://github.com/NeuronRobotics/nrjavaserial/blob/13fd9e19e5d03bcf8d52e694675311bdbcddf45f/src/main/java/gnu/io/RXTXCommDriver.java#L413-L422
We call this method to see what the available serial ports are so we have an up to date list of identifiers so the user can select between available ports in the UI.