Develop Reference

java io netty how to get next packet from a client

I am writing a minecraft server in java from scratch for private reasons.
I am new to the netty api so please explain how I can fix it
My problem is pretty simple my server waits for a connection then reads data from that connection but it never reads the then bit of info
https://wiki.vg/Server_List_Ping
I followed that and everything goes well up until the request packet which my server never reads it?
I don't know what the problem is I think it's because its closing the connection but I have no idea how to stop that
Here's the code
public class DataHandler extends SimpleChannelInboundHandler {
public void initChannel(NioServerSocketChannel nioServerSocketChannel) throws Exception {
try {
System.out.println("Data Handler");
}catch (Exception e) {
}
}
#Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
System.out.println("[DEBUG] Read complete");
//ctx.writeAndFlush(Unpooled.EMPTY_BUFFER)
// .addListener(ChannelFutureListener.CLOSE);
}
#Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
System.out.println("Data Handler active");
ctx.channel().read();
//ctx.pipeline().addLast("encoder",new Encoder());
//ctx.fireChannelActive();
}
private int pos = 0;
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
ByteBuf buf = (ByteBuf) msg;
//ByteBuf packet = buf.readBytes(length);
int length = readVarInt(buf);
int ID = readVarInt(buf);
System.out.println("[DEBUG] PACKET ID: "+ID);
Packet packet = PacketUtil.createPacket(ID,length,buf,ctx);
packet.readBuf();
Object ran = null;
//super.channelRead(ctx, msg);
}
#Override
protected void channelRead0(ChannelHandlerContext channelHandlerContext, Object o) throws Exception {
System.out.println("Test");
}
}
There is some trial and error comments in there I did not know if I should have left them in
Heres the main class
public class Server {
private int port;
public void run() throws IOException {
port = 25565;
EventLoopGroup mainGroup = new NioEventLoopGroup();
EventLoopGroup threadGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(mainGroup, threadGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
protected void initChannel(SocketChannel socketChannel) throws Exception {
socketChannel.pipeline().addLast(new DataHandler());
}
})
.option(ChannelOption.SO_BACKLOG, 5)
.option(ChannelOption.AUTO_READ,true)
.childOption(ChannelOption.SO_KEEPALIVE, true);
ChannelFuture channelFuture = b.localAddress(port).bind().sync();
System.out.println(String.format("Started on port %d", port));
System.out.println("Registering packets");
PacketUtil.registerPackets();
}catch(InterruptedException e) {
}
}
}

Netty channel write not reaching handlers

I'm learning Netty and prototyping a simple app which sends an object over TCP. My issue is that when I call Channel.write from the server side with my message, it doesn't seem to reach the handlers in the pipeline. When I send a message from client to server, it works as expected.
Here's the code.
The server:
public class Main {
private int serverPort;
private EventLoopGroup bossGroup;
private EventLoopGroup workerGroup;
private ServerBootstrap boot;
private ChannelFuture future;
private SomeDataChannelDuplexHandler duplex;
private Channel ch;
public Main(int serverPort) {
this.serverPort = serverPort;
}
public void initialise() {
boot = new ServerBootstrap();
bossGroup = new NioEventLoopGroup();
workerGroup = new NioEventLoopGroup();
boot.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast("idleStateHandler", new IdleStateHandler(0, 0, 2));
// Inbound
ch.pipeline().addLast(new LengthFieldBasedFrameDecoder(65535, 0, 2, 0, 0));
ch.pipeline().addLast(new SomeDataDecoder());
// Outbound
ch.pipeline().addLast(new LengthFieldPrepender(2));
ch.pipeline().addLast(new SomeDataEncoder());
// In-Out
ch.pipeline().addLast(new SomeDataChannelDuplexHandler());
}
})
.option(ChannelOption.SO_BACKLOG, 128)
.childOption(ChannelOption.SO_KEEPALIVE, true);
}
public void sendMessage() {
SomeData fd = new SomeData("hello", "localhost", 1234);
ChannelFuture future = ch.writeAndFlush(fd);
future.addListener(new ChannelFutureListener() {
#Override
public void operationComplete(ChannelFuture future) throws Exception {
if (!future.isSuccess()) {
System.out.println("send error: " + future.cause().toString());
} else {
System.out.println("send message ok");
}
}
});
}
public void startServer(){
try {
future = boot.bind(serverPort)
.sync()
.addListener(new ChannelFutureListener() {
#Override
public void operationComplete(ChannelFuture future) throws Exception {
ch = future.channel();
}
});
} catch (InterruptedException e) {
// log failure
}
}
public void stopServer() {
workerGroup.shutdownGracefully()
.addListener(e -> System.out.println("workerGroup shutdown"));
bossGroup.shutdownGracefully()
.addListener(e -> System.out.println("bossGroup shutdown"));
}
public static void main(String[] args) throws InterruptedException {
Main m = new Main(5000);
m.initialise();
m.startServer();
final Scanner scanner = new Scanner(System.in);
System.out.println("running.");
while (true) {
final String input = scanner.nextLine();
if ("q".equals(input.trim())) {
break;
} else {
m.sendMessage();
}
}
scanner.close();
m.stopServer();
}
}
The duplex channel handler:
public class SomeDataChannelDuplexHandler extends ChannelDuplexHandler {
#Override
public void channelActive(ChannelHandlerContext ctx) {
System.out.println("duplex channel active");
ctx.fireChannelActive();
}
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
System.out.println("duplex channelRead");
if (msg instanceof SomeData) {
SomeData sd = (SomeData) msg;
System.out.println("received: " + sd);
} else {
System.out.println("some other object");
}
ctx.fireChannelRead(msg);
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
#Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
if (evt instanceof IdleStateEvent) {
IdleStateEvent event = (IdleStateEvent) evt;
if (event.state() == IdleState.ALL_IDLE) { // idle for no read and write
System.out.println("idle: " + event.state());
}
}
}
}
And finally the encoder (the decoder is similar):
public class SomeDataEncoder extends MessageToByteEncoder<SomeData> {
#Override
protected void encode(ChannelHandlerContext ctx, SomeData msg, ByteBuf out) throws Exception {
System.out.println("in encoder, msg = " + msg);
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(msg.getName());
oos.writeObject(msg.getIp());
oos.writeInt(msg.getPort());
oos.close();
byte[] serialized = bos.toByteArray();
int size = serialized.length;
ByteBuf encoded = ctx.alloc().buffer(size);
encoded.writeBytes(bos.toByteArray());
out.writeBytes(encoded);
}
}
The client side:
public class Client {
String host = "10.188.36.66";
int port = 5000;
EventLoopGroup workerGroup = new NioEventLoopGroup();
ChannelFuture f;
private Channel ch;
public Client() {
}
public void startClient() throws InterruptedException {
Bootstrap boot = new Bootstrap();
boot.group(workerGroup);
boot.channel(NioSocketChannel.class);
boot.option(ChannelOption.SO_KEEPALIVE, true);
boot.handler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
// Inbound
ch.pipeline().addLast(new LengthFieldBasedFrameDecoder(65535, 0, 2, 0, 0));
ch.pipeline().addLast(new SomeDataDecoder());
// Outbound
ch.pipeline().addLast(new LengthFieldPrepender(2));
ch.pipeline().addLast(new SomeDataEncoder());
// Handler
ch.pipeline().addLast(new SomeDataHandler());
}
});
// Start the client
f = boot.connect(host, port).sync();
f.addListener(new ChannelFutureListener() {
public void operationComplete(ChannelFuture future) throws Exception {
System.out.println("connected to server");
ch = f.channel();
}
});
}
public void stopClient() {
workerGroup.shutdownGracefully();
}
private void writeMessage(String input) {
SomeData data = new SomeData("client", "localhost", 3333);
ChannelFuture fut = ch.writeAndFlush(data);
fut.addListener(new ChannelFutureListener() {
#Override
public void operationComplete(ChannelFuture future) throws Exception {
System.out.println("send message");
}
});
}
public static void main(String[] args) throws InterruptedException {
Client client = new Client();
client.startClient();
System.out.println("running.\n\n");
final Scanner scanner = new Scanner(System.in);
while (true) {
final String input = scanner.nextLine();
if ("q".equals(input.trim())) {
break;
} else {
client.writeMessage(input);
}
}
scanner.close();
client.stopClient(); //call this at some point to shutdown the client
}
}
and the handler:
public class SomeDataHandler extends SimpleChannelInboundHandler<SomeData> {
private ChannelHandlerContext ctx;
#Override
public void channelActive(ChannelHandlerContext ctx) {
System.out.println("connected");
this.ctx = ctx;
}
#Override
protected void channelRead0(ChannelHandlerContext ctx, SomeData msg) throws Exception {
System.out.println("got message: " + msg);
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
System.out.println("caught exception: " + cause.getMessage());
ctx.close();
}
}
When I send a message via the console on the server side, I get the output:
running.
duplex channel active
duplex read
idle: ALL_IDLE
idle: ALL_IDLE
send message ok
So it looks as though the message is sent but nothing is received on the client side.
When I do it from the client side I get (on the server console):
in decoder, numBytes in message = 31
duplex channelRead
received: SomeData [name=client, ip=localhost, port=3333]
which is what I expect.
So where's the problem? Is it something to do with using a ChannelDuplexHandler on the server side and a SimpleChannelInboundHandler on the client side? Is there something I need to call to kick the message down the pipeline?
UPDATE
I've added a check for future.isSuccess() in the server sendMessage method and I get
send error: java.lang.UnsupportedOperationException on the console.

(Posted on behalf of the OP).
For anyone who's interested, the problem was that I was trying to send the message on the server channel and not the normal channel. This post pointed me in the right direction.

using netty library, server unable to handle the reconnection scenario of client

Initially able to make the connection. Simply close the connection client and try to connect again or restart the client. the connection is not established. It creates connection only once.
Can someone help me to improve it. So, it can handle n number client simultaneously.
bossGroup = new NioEventLoopGroup(1);
workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).option(ChannelOption.SO_BACKLOG, 100)
.handler(new LoggingHandler(LogLevel.INFO)).childHandler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline p = ch.pipeline();
p.addLast(new DelimiterBasedFrameDecoder(20000, Delimiters.lineDelimiter()));
// p.addLast(new StringDecoder());
// p.addLast(new StringEncoder());
p.addLast(serverHandler);
}
});
// Start the server.
LOGGER.key("Simulator is opening listen port").low().end();
ChannelFuture f = b.bind(config.getPort()).sync();
LOGGER.key("Simulator started listening at port: " + config.getPort()).low().end();
// Wait until the server socket is closed.
f.channel().closeFuture().sync();
} finally {
// Shut down all event loops to terminate all threads.
LOGGER.key("Shtting down all the thread if anyone is still open.").low().end();
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
Server Handler code is below:
public class SimulatorServerHandler extends SimpleChannelInboundHandler<String> {
private AtomicReference<ChannelHandlerContext> ctxRef = new AtomicReference<ChannelHandlerContext>();
private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
private AtomicInteger seqNum = new AtomicInteger(1);
private final Configuration configure;
private ScheduledFuture<?> hbTimerWorker;
private final int stx = 0x02;
private final int etx = 0x03;
private final ILogger LOGGER;
public int enablePublishFunction = 0;
public SimulatorServerHandler(Configuration config) {
this.configure = config;
//LOGGER = LogFactory.INSTANCE.createLogger();
LOGGER = new LogFactory().createLogger("SIM SERVER");
}
#Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
ctxRef.set(ctx);
enablePublishFunction =1;
// System.out.println("Connected!");
LOGGER.low().key("Gateway connected to the Simulator ").end();
startHBTimer();
}
#Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
ctx.fireChannelInactive();
hbTimerWorker.cancel(false);
enablePublishFunction =0;
LOGGER.low().key("Gateway disconnected from the Simulator ").end();
}
#Override
public void channelRead0(ChannelHandlerContext ctx, String request) {
// Generate and write a response.
String response;
boolean close = false;
/* if (request.isEmpty()) {
response = "Please type something.\r\n";
} else if ("bye".equals(request.toLowerCase())) {
response = "Have a good day!\r\n";
close = true;
} else {
response = "Did you say '" + request + "'?\r\n";
}
// We do not need to write a ChannelBuffer here.
// We know the encoder inserted at TelnetPipelineFactory will do the conversion.
ChannelFuture future = ctx.write(response);
// Close the connection after sending 'Have a good day!'
// if the client has sent 'bye'.
if (close) {
future.addListener(ChannelFutureListener.CLOSE);
}
*/
System.out.println(request);
}
#Override
public void channelReadComplete(ChannelHandlerContext ctx) {
ctx.flush();
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
LOGGER.key("Unknown exception while network communication :"+ cause.getStackTrace()).high().end();
cause.printStackTrace();
ctx.close();
}

Maybe because you use always the very same server handler in your pipeline for all connections (not using new ServerHandler())? Side effects in your implementation could block your handler to be reusable.

Unable to receive response in client from netty server

I am new to Netty and trying to writing a server client project using it. I am able to send the request from client to the server successfully and am able to process it too using my listeners. But the issue am having is when I try to write the response back to the channel for the client processing on the server side using channel.write(), I am unable to get it back at client.
This is my first time on stackoverflow, please forgive if I make some mistake while asking the question or for indentation issues while posting the code.
This is my server :
public class SocketIOServer {
private Logger log = Logger.getLogger(getClass());
private ServerBootstrap bootstrap;
private Channel serverChannel;
private int port;
private boolean running;
public SocketIOServer(int port) {
this.port = port;
this.running = false;
}
public boolean isRunning() {
return this.running;
}
public void start() {
bootstrap = new ServerBootstrap(new NioServerSocketChannelFactory(
Executors.newCachedThreadPool(),
Executors.newCachedThreadPool()));
try {
EncryptionManager encryptionManager = EncryptionManager.getInstance();
} catch (Exception ex) {
java.util.logging.Logger.getLogger(SocketIOServer.class.getName()).log(Level.SEVERE, null, ex);
}
// Set up the event pipeline factory.
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
#Override
public ChannelPipeline getPipeline() throws Exception {
ChannelPipeline pipeline = pipeline();
pipeline.addLast("decode", new FrameDecoder(){
#Override
protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception {
// Make sure if the length field was received.
if (buf.readableBytes() < 4) {
// The length field was not received yet - return null.
// This method will be invoked again when more packets are
// received and appended to the buffer.
return null;
}
// The length field is in the buffer.
// Mark the current buffer position before reading the length field
// because the whole frame might not be in the buffer yet.
// We will reset the buffer position to the marked position if
// there's not enough bytes in the buffer.
buf.markReaderIndex();
// Read the length field.
int length = buf.readInt();
// Make sure if there's enough bytes in the buffer.
if (buf.readableBytes() < length) {
// The whole bytes were not received yet - return null.
// This method will be invoked again when more packets are
// received and appended to the buffer.
// Reset to the marked position to read the length field again
// next time.
buf.resetReaderIndex();
return null;
}
// There's enough bytes in the buffer. Read it.
ChannelBuffer frame = buf.readBytes(length);
// Successfully decoded a frame. Return the decoded frame.
return frame;
}
});
pipeline.addLast("handler", new GameServerHandler());
return pipeline;
}
});
bootstrap.setOption("backlog", 1024);
// Bind and start to accept incoming connections.
this.serverChannel = bootstrap.bind(new InetSocketAddress(port));
this.running = true;
log.info("Server Started at port [" + port + "]");
System.out.println("Server Started at port [" + port + "]");
}
public static void main(String[] args) {
SocketIOServer server = new SocketIOServer(8888);
server.start();
}
Server Handler class :
public class GameServerHandler extends SimpleChannelUpstreamHandler {
#Override
public void handleUpstream(
ChannelHandlerContext ctx, ChannelEvent e) throws Exception {
if (e instanceof ChannelStateEvent) {
logger.info(e.toString());
}
super.handleUpstream(ctx, e);
}
#Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception{
System.out.println("Following data recieved at the server");
ConnectionManager connectionManager = ConnectionManager.getInstance();
List<Object> paramsList = new ArrayList<Object>();
NetworkClient client = connectionManager.getNetworkClient(e.getChannel().getId());
ChannelBuffer ebuf = (ChannelBuffer)e.getMessage();
if( client == null ) {
client = new NetworkClient(e.getChannel());
connectionManager.addNetworkClient(e.getChannel().getId(), client);
}
byte [] encryptedData = ebuf.array();
System.out.println("encrypted data size : "+ encryptedData.length);
System.out.println("encrypted data : "+ encryptedData);
byte [] decrpytedData = null;
try {
decrpytedData = EncryptionManager.getInstance().decrypt(encryptedData, EncryptionManager.getInstance().getPrivateKey());
}catch (Throwable ee){
ee.printStackTrace();
}
ChannelBuffer buf = ChannelBuffers.buffer(decrpytedData.length);
buf.writeBytes(decrpytedData);
while(buf.readable()) {
long gameTableId = buf.readLong();
GameTable gameTable = gameTableController.getTablePeer(gameTableId);
if(gameTable == null) {
GameTable newGameTable = new GameTable();
newGameTable.setTableId(gameTableId);
newGameTable.registerListeners();
gameTableController.storeTablePeer(gameTableId, newGameTable);
}
int eventHash = buf.readInt();
String eventName = getEventNameFromEventHash(eventHash);
int paramCount = buf.readInt();
if(paramCount > 0) {
for(int count=0;count<paramCount;count++) {
populateParamList(buf, paramsList);
}
if(!NetworkMessenger.broadcastToAllFromNetwork(eventName, client, paramsList.toArray(new Object[paramsList.size()]))) {
logger.debug( "Unhandled Data:" + eventName);
System.out.println("Unhandled Data:" + eventName);
}
logger.debug( "Data processed successfully for " + eventName + " game table id : " + gameTableId);
System.out.println("Data processed successfully for " + eventName + " game table id : " + gameTableId);
}
break;
}
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
e.getCause().printStackTrace();
logger.log(
Level.WARN,
"Unexpected exception from downstream.",
e.getCause());
Channel ch = e.getChannel();
ch.close();
}
#Override
public void channelConnected(
ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
ChannelFuture cf = e.getFuture();
cf.addListener(new Greeter());
}
#Override
public void channelDisconnected(
ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
// Unregister the channel from the global channel list
// so the channel does not receive messages anymore.
channels.remove(e.getChannel());
}
private static final class Greeter implements ChannelFutureListener {
public void operationComplete(ChannelFuture future) throws Exception {
if (future.isSuccess()) {
// Once session is secured, send a greeting.
String welcomeMsg = "Welcome";
ChannelBuffer cb = ChannelBuffers.dynamicBuffer();
cb.writeBytes(welcomeMsg.getBytes());
future.getChannel().write(cb);
// Register the channel to the global channel list
// so the channel received the messages from others.
channels.add(future.getChannel());
} else {
future.getChannel().close();
}
}
}
}
This is my client class :
public class Clientbot {
public static void main(String[] args) throws IOException {
String host = "localhost";
int port = 8888;
final ChannelBuffer buf = ChannelBuffers.dynamicBuffer();
// Configure the client.
ChannelFactory factory =
new NioClientSocketChannelFactory(
Executors.newCachedThreadPool(),
Executors.newCachedThreadPool());
ClientBootstrap bootstrap = new ClientBootstrap(factory);
bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
public ChannelPipeline getPipeline() {
ChannelPipeline pipeline = Channels.pipeline();
pipeline.addLast("decode", new FrameDecoder(){
#Override
protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buf) throws Exception {
// Make sure if the length field was received.
if (buf.readableBytes() < 4) {
return null;
}
buf.markReaderIndex();
// Read the length field.
int length = buf.readInt();
// Make sure if there's enough bytes in the buffer.
if (buf.readableBytes() < length) {
buf.resetReaderIndex();
return null;
}
// There's enough bytes in the buffer. Read it.
ChannelBuffer frame = buf.readBytes(length);
// Successfully decoded a frame. Return the decoded frame.
return frame;
}
});
pipeline.addLast("handler", new ClientHandler());
return pipeline;
}
});
bootstrap.setOption("tcpNoDelay", true);
bootstrap.setOption("keepAlive", true);
ChannelFuture future = bootstrap.connect(new InetSocketAddress(host, port));
// Wait until the connection attempt succeeds or fails.
Channel channel = future.awaitUninterruptibly().getChannel();
if (!future.isSuccess()) {
future.getCause().printStackTrace();
bootstrap.releaseExternalResources();
return;
}
ChannelFuture lastWriteFuture = null;
try {
lastWriteFuture = writeSecureSampleData(channel, buf);
} catch (Exception ex) {
ex.printStackTrace();
}
// Wait until all messages are flushed before closing the channel.
if (lastWriteFuture != null) {
lastWriteFuture.awaitUninterruptibly();
}
// Close the connection. Make sure the close operation ends because
// all I/O operations are asynchronous in Netty.
channel.close().awaitUninterruptibly();
// Shut down all thread pools to exit.
bootstrap.releaseExternalResources();
}
private static ChannelFuture writeSecureSampleData(Channel channel, ChannelBuffer buffer) throws Exception {
long gameId = 1234;
ChannelBuffer buf = ChannelBuffers.buffer(256);
buf.writeLong(gameId);
writeParamsForLogin(buf);
byte [] data = buf.array();
byte [] encryptedData = EncryptionManager.getInstance().encrypt(data, EncryptionManager.getInstance().getPublicKey());
int size = encryptedData.length;
buffer.writeInt(size);
buffer.writeBytes(encryptedData);
ChannelFuture writeFuture = channel.write(buffer);
return writeFuture;
}
private static void writeParamsForLogin(ChannelBuffer buf) {
int eventHash = getEventHash("Login");
buf.writeInt(eventHash);
int paramCount = 3 ; // in case of PlayerToken 2 parameters to be send : player id + player token
buf.writeInt(paramCount);
// version , E , N
String version = "1.0";
buf.writeInt(dataType_String);
buf.writeInt(version.length());
buf.writeBytes(version.getBytes());
String E = "61";
buf.writeInt(dataType_ByteArray);
buf.writeInt(E.length());
buf.writeBytes(E.getBytes());
String N = "53";
buf.writeInt(dataType_ByteArray);
buf.writeInt(N.length());
buf.writeBytes(N.getBytes());
}
}
and the client handler class :
public class ClientHandler extends SimpleChannelUpstreamHandler {
#Override
public void messageReceived(
ChannelHandlerContext ctx, MessageEvent e) {
System.err.println(e.getMessage());
System.out.println("Message Recieved");
ChannelBuffer buf = (ChannelBuffer)e.getMessage();
while (buf.readable()) {
System.out.println((char) buf.readByte());
System.out.flush();
}
}
#Override
public void exceptionCaught(
ChannelHandlerContext ctx, ExceptionEvent e) {
logger.log(
Level.WARNING,
"Unexpected exception from downstream.",
e.getCause());
e.getCause().printStackTrace();
e.getChannel().close();
}
}
On receiving the request data on the server, I am processing it and writing back the response using the following method :
private static boolean sendMessage(NetworkClient targetObject, String eventName, Object[] params) {
logger.debug("Sending message for the event : " + eventName);
if(targetObject == null) {
sendMessageToAll(eventName, params);
} else {
if (targetObject.getClientChannel() == null) {
logger.error("Target not defined.");
return false;
}
Channel clientChannel = targetObject.getClientChannel();
ChannelBuffer buf = ChannelBuffers.dynamicBuffer();
long hash = getHashString(eventName);
buf.writeInt(512);
buf.writeLong(hash);
if(params != null) {
buf.writeInt(params.length);
for(Object param : params) {
int type = getTypeOfObject(param);
buf.writeInt(type);
writeParamToBuffer(buf, type, param);
}
}
ChannelFuture cf = null;
try {
cf = clientChannel.write(buf);
if(cf.isSuccess()){
System.out.println("Written to client successfully");
}
} catch (Exception e) {
logger.error("Error in broadcasting for event : " + eventName, e);
} finally {
}
}
return false;
}
This code is still a work in progress, so you might find lot of "not required" stuff in there. I just wanted to show the logic that I am trying to use and want to know why it is not working.
I have taken help from examples at http://docs.jboss.org/netty/3.2/xref/org/jboss/netty/example/ for writing this.
Thanks in advance for any help.

Very complete code.
An easy way to write text to a websockets channel is to do this:
ChannelFuture writeFuture = channel.write(new TextWebSocketFrame("My Text here!");
You don't need to deal with the ChannelBuffers directly. That may resolve your problem.

Basic Netty echo server - string encoder error?

This is my first time using Netty and I'm having trouble making a simple echo server! I looked at docs and it says to use the string encoder and decoder, which I am not using properly apparently. For the framedecoder, I'd like to use the header messages with one byte length, but that doesn't seem to be working either due to the string issue. I assume my implementation of the PipelineFactory is messed up.
Bonus Question:
Because I'm stupid and ambitious, I tried implementing a timeout/heartbeat handler. That didn't work either.
Here are the console output and java code:
Console:
>>telnet localhost 6969
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
>>3
Connection closed by foreign host.
Java Console:
Starting server on 6969
channelConnected
channelDisconnected
java.lang.IllegalArgumentException: unsupported message type: class java.lang.String
at org.jboss.netty.channel.socket.nio.SocketSendBufferPool.acquire(SocketSendBufferPool.java:51)
at org.jboss.netty.channel.socket.nio.NioWorker.write0(NioWorker.java:455)
...
Server.java
public class Server {
public static void main(String[] args) throws Exception {
ChannelFactory factory =
new NioServerSocketChannelFactory(
Executors.newCachedThreadPool(),
Executors.newCachedThreadPool());
ServerBootstrap bootstrap = new ServerBootstrap(factory);
Timer timer = new HashedWheelTimer();
bootstrap.setPipelineFactory(new MyPipelineFactory(timer) {
public ChannelPipeline getPipeline() {
return Channels.pipeline(new ServerHandler());
}
});
bootstrap.setOption("child.tcpNoDelay", true);
bootstrap.setOption("child.keepAlive", true);
bootstrap.bind(new InetSocketAddress(6969));
System.out.println("Starting server on 6969");
}
}
ServerHandler.java
public class ServerHandler extends SimpleChannelHandler {
#Override
public void channelConnected(ChannelHandlerContext ctx, ChannelStateEvent e){
Channel ch = e.getChannel();
System.out.println("channelConnected");
}
#Override
public void channelDisconnected(ChannelHandlerContext ctx, ChannelStateEvent e){
Channel ch = e.getChannel();
System.out.println("channelDisconnected");
}
#Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
String msg = (String) e.getMessage();
e.getChannel().write("Did you say '" + msg + "'?\n");
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) {
e.getCause().printStackTrace();
Channel ch = e.getChannel();
ch.close();
}
}
MyPipelineFactory.java
public class MyPipelineFactory implements ChannelPipelineFactory {
private final Timer timer;
private static ChannelHandler idleStateHandler;
public MyPipelineFactory(Timer t) {
this.timer = t;
//this.idleStateHandler = new IdleStateHandler(timer, 5, 20, 0); // timer must be shared
}
public ChannelPipeline getPipeline() {
// create default pipeline from static method
ChannelPipeline pipeline = Channels.pipeline();
// Decoders
int maxFrameLength = 1024;
pipeline.addLast("framer", new DelimiterBasedFrameDecoder(maxFrameLength, Delimiters.lineDelimiter()));
//pipeline.addLast("frameDecoder", new LengthFieldBasedFrameDecoder(maxFrameLength,0,1)); // get header from message
pipeline.addLast("stringDecoder", new StringDecoder(CharsetUtil.UTF_8));
// Encoders
pipeline.addLast("stringEncoder", new StringEncoder(CharsetUtil.UTF_8));
// Idle state handling- heartbeat
//pipeline.addLast("idleStateHandler", idleStateHandler);
return pipeline;
}
}
Bonus, because I'm stupid and want to get in over my head...
HeartbeatHandler.java
public class HeartbeatHandler extends IdleStateAwareChannelHandler {
#Override
public void channelIdle(ChannelHandlerContext ctx, IdleStateEvent e) {
if (e.getState() == IdleState.READER_IDLE) {
System.out.println("Reader idle, closing channel");
e.getChannel().close();
}
else if (e.getState() == IdleState.WRITER_IDLE) {
System.out.println("Writer idle, sending heartbeat");
e.getChannel().write("heartbeat"); //
}
}
}

It's because you mess up the ChannelPipeline.
You use:
bootstrap.setPipelineFactory(new MyPipelineFactory(timer) {
public ChannelPipeline getPipeline() {
return Channels.pipeline(new ServerHandler());
}
});
What you would need todo is modify the MyPipelineFactory class and add your ServerHandler in there. Then just set it like:
bootstrap.setPipelineFactory(new MyPipelineFactory(timer));
Then everything should work. Even your timeout stuff ;)