/**
* Creates and starts the {@link #sendKeepAliveMessageThread} which is to send STUN keep-alive
* <tt>Message</tt>s to the STUN server associated with the <tt>StunCandidateHarvester</tt> of
* this instance in order to keep the <tt>Candidate</tt>s harvested by this instance alive.
*/
private void createSendKeepAliveMessageThread() {
synchronized (sendKeepAliveMessageSyncRoot) {
Thread t = new SendKeepAliveMessageThread(this);
t.setDaemon(true);
t.setName(getClass().getName() + ".sendKeepAliveMessageThread: " + hostCandidate);
boolean started = false;
sendKeepAliveMessageThread = t;
try {
t.start();
started = true;
} finally {
if (!started && (sendKeepAliveMessageThread == t)) sendKeepAliveMessageThread = null;
}
}
}
/**
* Runs in {@link #sendKeepAliveMessageThread} to notify this instance that
* <tt>sendKeepAliveMessageThread</tt> is about to exit.
*/
private void exitSendKeepAliveMessageThread() {
synchronized (sendKeepAliveMessageSyncRoot) {
if (sendKeepAliveMessageThread == Thread.currentThread()) sendKeepAliveMessageThread = null;
/*
* Well, if the currentThread is finishing and this instance is
* still to send keep-alive messages, we'd better start another
* Thread for the purpose to continue the work that the
* currentThread was supposed to carry out.
*/
if ((sendKeepAliveMessageThread == null)
&& (sendKeepAliveMessageInterval != SEND_KEEP_ALIVE_MESSAGE_INTERVAL_NOT_SPECIFIED)) {
createSendKeepAliveMessageThread();
}
}
}
/**
* Runs in {@link #sendKeepAliveMessageThread} and sends STUN keep-alive <tt>Message</tt>s to the
* STUN server associated with the <tt>StunCandidateHarvester</tt> of this instance.
*
* @return <tt>true</tt> if the method is to be invoked again; otherwise, <tt>false</tt>
*/
private boolean runInSendKeepAliveMessageThread() {
synchronized (sendKeepAliveMessageSyncRoot) {
// Since we're going to #wait, make sure we're not canceled yet.
if (sendKeepAliveMessageThread != Thread.currentThread()) return false;
if (sendKeepAliveMessageInterval == SEND_KEEP_ALIVE_MESSAGE_INTERVAL_NOT_SPECIFIED) {
return false;
}
// Determine the amount of milliseconds that we'll have to #wait.
long timeout;
if (sendKeepAliveMessageTime == -1) {
/*
* If we're just starting, don't just go and send a new STUN
* keep-alive message but rather wait for the whole interval.
*/
timeout = sendKeepAliveMessageInterval;
} else {
timeout =
sendKeepAliveMessageTime + sendKeepAliveMessageInterval - System.currentTimeMillis();
}
// At long last, #wait if necessary.
if (timeout > 0) {
try {
sendKeepAliveMessageSyncRoot.wait(timeout);
} catch (InterruptedException iex) {
}
/*
* Apart from being the time to send the STUN keep-alive
* message, it could be that we've experienced a spurious
* wake-up or that we've been canceled.
*/
return true;
}
}
sendKeepAliveMessageTime = System.currentTimeMillis();
try {
sendKeepAliveMessage();
} catch (StunException sex) {
logger.log(Level.INFO, "Failed to send STUN keep-alive message.", sex);
}
return true;
}