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Please have a look at my original question: Optimizing code using semaphore to control Netty channel pool

I have made some changes as pointed out by @rolfl The new code is as follows. Is this better? Can i remove the synchronization blocks with some other methodology?

public enum Client{
 INSTANCE(Config.getServerIp(),Config.getServerPort());
 private static final Logger s_logger = Logger.getLogger(Client.class);
 private final String host;
 private final int port;
 private boolean[] used = null;
 private Semaphore available = null;
 private Channel[] channels = null;
 private final Bootstrap b;
 private Client(String host, int port){
 this.host = host;
 this.port = port;
 used = new boolean[Config.getMaxConnections()];
 available = new Semaphore(Config.getMaxConnections());
 channels = new Channel[Config.getMaxConnections()];
 EventLoopGroup workerGroup = new NioEventLoopGroup();
 final ChannelInitializer<SocketChannel> channelInitializer = new BasicNioClientChannelInitializer();
 b = new Bootstrap();
 b.group(workerGroup)
 .channel(NioSocketChannel.class)
 .handler(channelInitializer)
 .option(ChannelOption.SO_KEEPALIVE, true);
 }
 public int sendMessage(final String message) throws Exception{
 final String messageToSend = message + "\r\n";
 int responseCode = 200;
 available.acquire();
 try {
 Channel ch;
 boolean activeChannel;
 int i;
 synchronized (this) {
 ch = null;
 activeChannel = false;
 for (i = 0; i < Config.getMaxConnections(); i++) {
 if (!used[i]) {
 used[i] = true;
 ch = channels[i];
 break; 
 }
 }
 if (i == Config.getMaxConnections()) {
 //Should never happen
 throw new Exception("No unsused connections.");
 }
 try {
 activeChannel = ch != null ? ch.isActive() : false;
 if (!activeChannel) {
 if (ch != null) {
 ch.close();
 } 
 ChannelFuture cf = b.connect(host, port);
 boolean connect = cf.await(Config.getMaxWaitInMillisToConnect());
 if (!connect) {
 throw new Exception("Unable to try connection to Server in " + Config.getMaxWaitInMillisToConnect() + "ms");
 }
 ch = cf.channel();
 channels[i] = ch;
 activeChannel = ch.isActive();
 }
 } catch (Exception e) {
 responseCode = 404;
 s_logger.log(Level.FATAL, "***** Could not Connect to Server ****");
 s_logger.log(Level.FATAL, e);
 e.printStackTrace();
 }
 }
 try {
 if (activeChannel) {
 System.out.println("Sending to Server using Channel: " + i + " data: " + message);
 ChannelFuture future = ch.writeAndFlush(messageToSend);
 } else {
 throw new Exception("Unable to connect to Server.");
 } 
 } catch (Exception e) {
 responseCode = 404;
 s_logger.log(Level.FATAL, "***** Could not Connect to Server ****");
 s_logger.log(Level.FATAL, e);
 e.printStackTrace();
 }
 synchronized (this) {
 for (int j = 0; j < Config.getMaxConnections(); j++) {
 if (ch == channels[j]) {
 if (used[j]) {
 used[j] = false;
 break;
 }
 }
 }
 }
 } finally {
 available.release();
 } 
 return responseCode;
 }
}