I am getting intermittent (rare, but causing fatal shutdown) exceptions when pinging NetworkServerControl:

2010-08-02 15:31:25,491 [ApacheDerbyServer] INFO  components.DerbyServerComponent  - 2010-08-02 19:31:25.491 GMT : Error on client socket:Socket closed
2010-08-02 15:31:25,492 [ApacheDerbyServer] INFO  components.DerbyServerComponent  - 2010-08-02 19:31:25.492 GMT : Socket closed
2010-08-02 15:31:25,492 [ApacheDerbyServer] INFO  components.DerbyServerComponent  - java.net.SocketException: Socket closed
2010-08-02 15:31:25,492 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at java.net.SocketInputStream.socketRead0(Native Method)
2010-08-02 15:31:25,493 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at java.net.SocketInputStream.read(SocketInputStream.java:129)
2010-08-02 15:31:25,493 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at java.net.SocketInputStream.read(SocketInputStream.java:90)
2010-08-02 15:31:25,493 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at org.apache.derby.impl.drda.NetworkServerControlImpl.fillReplyBuffer(Unknown Source)
2010-08-02 15:31:25,494 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at org.apache.derby.impl.drda.NetworkServerControlImpl.readResult(Unknown Source)
2010-08-02 15:31:25,494 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at org.apache.derby.impl.drda.NetworkServerControlImpl.pingWithNoOpen(Unknown Source)
2010-08-02 15:31:25,494 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at org.apache.derby.impl.drda.NetworkServerControlImpl.ping(Unknown Source)
2010-08-02 15:31:25,495 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at org.apache.derby.drda.NetworkServerControl.ping(Unknown Source)
2010-08-02 15:31:25,495 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at com.jefco.fi.geni.components.DerbyServerComponent.run(DerbyServerComponent.java:142)
2010-08-02 15:31:25,495 [ApacheDerbyServer] INFO  components.DerbyServerComponent  -    at java.lang.Thread.run(Thread.java:619)
2010-08-02 15:31:25,496 [ApacheDerbyServer] ERROR components.DerbyServerComponent  - Error while pinging NetworkServerControl:
java.net.SocketException: Socket closed
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:129)
        at java.net.SocketInputStream.read(SocketInputStream.java:90)
        at org.apache.derby.impl.drda.NetworkServerControlImpl.fillReplyBuffer(Unknown Source)
        at org.apache.derby.impl.drda.NetworkServerControlImpl.readResult(Unknown Source)
        at org.apache.derby.impl.drda.NetworkServerControlImpl.pingWithNoOpen(Unknown Source)
        at org.apache.derby.impl.drda.NetworkServerControlImpl.ping(Unknown Source)
        at org.apache.derby.drda.NetworkServerControl.ping(Unknown Source)

My code pings the NSC in two places - there is one thread which implements run() method like this:

final public void run() {
        final Thread currentThread = Thread.currentThread();

        try {
            m_server = new NetworkServerControl(m_host, m_port);
            m_server.start(new PrintWriter(new LoggingOutputStream(logger, Level.INFO), true));

            try {
                while (m_thread == currentThread) {
                    try {

                        if (logger.isTraceEnabled()) {
                            logger.trace("Pinging NetworkServerControl on [" + m_host + ":" + m_port + "]");

--->                        m_server.ping();   <--- Exception Thrown
                    } catch (InterruptedException e) {
                        logger.info(toString() + " sleep has been interrupted");
            } catch (Exception e) {
                logger.error("Error while pinging NetworkServerControl:", e);

            logger.info("Stopping NetworkServerControl on [" + m_host + ":" + m_port + "]");
        } catch (Exception e) {
            logger.error("Error while starting/stopping NetworkServerControl:", e);

And another "validating" thread calls this method at regular intervals:

    final public String isRuntimeValid() {
        final StringBuilder builder = new StringBuilder();

        if (m_server == null) builder.append("\n\t").append("Server is null");
        if (m_thread == null) builder.append("\n\t").append("Thread is null");

        try {
        } catch (Exception e) {
            builder.append("\n\t").append("Server cannot be pinged");

        return builder.toString();

Can there be any problem if those two are called at around the same time? This is probably the only scenario which could, I imagine, cause a problem...
Would anyone have any other thoughts or suspicions?

Much appreciated,


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