TcpReplicationThread() 
{

}

 protected  void drainChannel(SelectionKey key) throws Exception 
{
        boolean packetReceived=false;
        SocketChannel channel = (SocketChannel) key.channel();
        int count;
        buffer.clear();			// make buffer empty
        ObjectReader reader = (ObjectReader)key.attachment();
        // loop while data available, channel is non-blocking
        while ((count = channel.read (buffer))  > 0) {
            buffer.flip();		// make buffer readable
            reader.append(buffer.array(),0,count);
            buffer.clear();		// make buffer empty
        }
        //check to see if any data is available
        int pkgcnt = reader.execute();
        if (log.isTraceEnabled()) {
            log.trace("sending " + pkgcnt + " ack packages to " + channel.socket().getLocalPort() );
        }
        if (sendAck) {
            while ( pkgcnt  > 0 ) {
                sendAck(key,channel);
                pkgcnt--;
            }
        }
        if (count <  0) {
            // close channel on EOF, invalidates the key
            channel.close();
            return;
        }
        //acquire the interestOps mutex
        Object mutex = this.getPool().getInterestOpsMutex();
        synchronized (mutex) {
            // cycle the selector so this key is active again
            key.selector().wakeup();
            // resume interest in OP_READ, OP_WRITE
            int resumeOps = key.interestOps() | SelectionKey.OP_READ;
            key.interestOps(resumeOps);
        }
}

The actual code which drains the channel associated with the given key. This method assumes the key has been modified prior to invocation to turn off selection interest in OP_READ. When this method completes it re-enables OP_READ and calls wakeup() on the selector so the selector will resume watching this channel.

 public synchronized  void run() 
{
        while (doRun) {
            try {
                // sleep and release object lock
                this.wait();
            } catch (InterruptedException e) {
                if(log.isInfoEnabled())
                    log.info("TCP worker thread interrupted in cluster",e);
                // clear interrupt status
                Thread.interrupted();
            }
            if (key == null) {
                continue;	// just in case
            }
            try {
                drainChannel (key);
            } catch (Exception e) {
                log.error ("TCP Worker thread in cluster caught '"
                    + e + "' closing channel", e);
                // close channel and nudge selector
                try {
                    key.channel().close();
                } catch (IOException ex) {
                    log.error("Unable to close channel.",ex);
                }
                key.selector().wakeup();
            }
            key = null;
            // done, ready for more, return to pool
            this.pool.returnWorker (this);
        }
}

 protected  void sendAck(SelectionKey key,
    SocketChannel channel) 
{
        
        try {
            channel.write(ByteBuffer.wrap(ACK_COMMAND));
            if (log.isTraceEnabled()) {
                log.trace("ACK sent to " + channel.socket().getPort());
            }
        } catch ( java.io.IOException x ) {
            log.warn("Unable to send ACK back through channel, channel disconnected?: "+x.getMessage());
        }
}

send a reply-acknowledgement (6,2,3)

 synchronized  void serviceChannel(SelectionKey key,
    boolean sendAck) 
{
        this.key = key;
        this.sendAck=sendAck;
        key.interestOps (key.interestOps() & (~SelectionKey.OP_READ));
        key.interestOps (key.interestOps() & (~SelectionKey.OP_WRITE));
        this.notify();		// awaken the thread
}

Called to initiate a unit of work by this worker thread on the provided SelectionKey object. This method is synchronized, as is the run() method, so only one key can be serviced at a given time. Before waking the worker thread, and before returning to the main selection loop, this key's interest set is updated to remove OP_READ. This will cause the selector to ignore read-readiness for this channel while the worker thread is servicing it.