Can I know jdwp transport port from inside JVM?

Question

I am starting java with the following arguments:
-Xdebug -Xrunjdwp:transport=dt_socket,address=0,server=y,suspend=n
and I get the following output:
Listening for transport dt_socket at address: 59183

Is it possible to find the port from inside the same JVM, without reading standard output?

Answer 1

Why are you setting the port to 0? Typically you would use the address parameter to set the port to whatever you want.

http://download.oracle.com/javase/1.4.2/docs/guide/jpda/conninv.html

Answer 2

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;

import java.lang.reflect.Method;
import java.util.Properties;

@Slf4j
public class RuntimeDebugger {

    static private int jdwpListenerPort;

    static public int getJdwpListenerPort() {
        if(jdwpListenerPort == 0) {
            jdwpListenerPort = readJdwpListenerPort();
        }
        return jdwpListenerPort;
    }

    static private int readJdwpListenerPort() {
        String listenerAddress = null;
        try {
            Class<?> theClass = Class.forName("sun.misc.VMSupport");
            Method m = theClass.getMethod("getAgentProperties");
            Properties p = (Properties) m.invoke(null);
            listenerAddress = p.getProperty("sun.jdwp.listenerAddress");
            if (listenerAddress != null) {
                listenerAddress = StringUtils.substringAfter(listenerAddress, ":");
                return Integer.parseInt(listenerAddress);
            }
        } catch (Exception ex) {
            log.error("Failed to read sun.jdwp.listenerAddress, ignore");
        }
        return -1;
    }
}