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Netty and Scheduled Executor Service

I'm trying to create a TCP server that read data periodically from a database (Redis) and send it to the appropriate client.
However, since I'm pretty new to Netty, I don't know how could I schedule this. I do know that I need to use a Scheduled Executor Service like this:
ScheduledExecutorService e = Executors.newSingleThreadScheduledExecutor();
e.scheduleAtFixedRate(() -> {
System.out.println("Calling...");
// Do something
}, 1, 1, TimeUnit.SECONDS);
However, when I tried to put that in the server code, It's only calling the method once. I've tried to put that in different place but still can't seem to get it right. What should I do?
Here's the code of the server:
package com.example.test.app;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class Server {
public static void main(String[] args) throws Exception
{
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
final ServerHandler handler = new ServerHandler();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup);
b.channel(NioServerSocketChannel.class);
b.childHandler(new ChannelInitializer<SocketChannel>() {
#Override
protected void initChannel(SocketChannel ch) throws Exception
{
ch.pipeline().addLast(handler);
}
});
b.option(ChannelOption.SO_BACKLOG, 128);
b.childOption(ChannelOption.SO_KEEPALIVE, true);
ScheduledExecutorService e = Executors.newSingleThreadScheduledExecutor();
e.scheduleAtFixedRate(() -> {
System.out.println("Calling...");
handler.saySomething();
}, 1, 1, TimeUnit.SECONDS);
ChannelFuture f = b.bind(1337).sync();
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
}
And here's the server handler:
package com.example.test.app;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
public class ServerHandler extends ChannelInboundHandlerAdapter {
private ChannelHandlerContext ctx;
#Override
public void channelActive(ChannelHandlerContext ctx)
{
this.ctx = ctx;
System.out.println("Someone's connedted!");
}
public void saySomething()
{
final ChannelFuture f = ctx.writeAndFlush("Sup!");
f.addListener((ChannelFutureListener) (ChannelFuture future) -> {
System.out.println("Something has been said!");
});
}
}

The method saySomething() generates NullPointerException for calling final ChannelFuture f = ctx.writeAndFlush("Sup!"); while ctx is null.
EventExecutorGroup.scheduleAtFixedRate javadoc description says that "If any execution of the task encounters an exception, subsequent executions are suppressed". So this is why you get is called only once...
Also, seems like Netty allows you to re-use a handler instance for different pipeline instances only if you annotate this handler's class as #Sharable. Otherwise, it will throw exception. If your handler is stateless (which is not your case, as yours has the ctx member) then you should annotate it as #Sharable and re-use it to all created pipelines. If it is stateful, create a new instance for every new pipeline (new client connection).
Finally, to schedule your task for each connected client you can use the executor which can be referenced by the ctx of the connected client's channel (by default, as in your case, the channel's EventLoop) on your channelActive() implementation. This executor implements ScheduledExecutorService, so you have also scheduleAtFixedRate.
Take a look at my version of your code and see if it suits you.
Server:
package com.example.test.app;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class Server {
public static void main(String[] args) throws Exception
{
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup);
b.channel(NioServerSocketChannel.class);
b.childHandler(new ChannelInitializer<SocketChannel>() {
#Override
protected void initChannel(SocketChannel ch) throws Exception
{
ch.pipeline().addLast(new ServerHandler());
}
});
b.option(ChannelOption.SO_BACKLOG, 128);
b.childOption(ChannelOption.SO_KEEPALIVE, true);
// ScheduledExecutorService e = Executors.newSingleThreadScheduledExecutor();
// e.scheduleAtFixedRate(() -> {
// System.out.println("Calling...");
// handler.saySomething();
// }, 1, 1, TimeUnit.SECONDS);
ChannelFuture f = b.bind(1337).sync();
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
}
ServerHandler:
package com.example.test.app;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
public class ServerHandler extends ChannelInboundHandlerAdapter {
private ScheduledFuture sf;
#Override
public void channelActive(ChannelHandlerContext ctx)
{
System.out.println("Someone's connedted! "+ctx.channel());
sf = ctx.executor().scheduleAtFixedRate(() -> {
System.out.println("Calling...");
saySomething(ctx);
}, 1, 1, TimeUnit.SECONDS);
}
#Override
public void channelInactive(ChannelHandlerContext ctx) {
System.out.println("Someone's disconnected! "+ctx.channel());
sf.cancel(false);
}
private void saySomething(ChannelHandlerContext ctx)
{
final ChannelFuture f = ctx.writeAndFlush("Sup!");
f.addListener((ChannelFutureListener) (ChannelFuture future) -> {
System.out.println("Something has been said!");
});
}
}

How to run jetty server for java junit testing

I am trying to write an integration test to spin up jetty server locally and then use client to communicate with the rest URI and call the business logic downstream. However, when I start my jetty server it does not relinquish the control, so my client is not executed. So I used threading to start my jetty in a different thread, however, the thread finishes before my client call, it says connection refused. Any approach I can take?
#Test
public void testPerform() {
final JettyServer jettyServer = JettyServer.create();
jettyServer.buildJettyServer(ServletContextHandler.SESSIONS, "/", 8080, TestResource.class);
Runnable runnable = new Runnable()
{
#Override
public void run()
{
jettyServer.start();
}
};
new Thread(runnable).start();
final javax.ws.rs.client.Client client = ClientBuilder.newClient();
final Response response = client.target("http://localhost:8080/test").request().post(Entity.text(""));
jettyServer.stop();
}

Skip the Runnable, skip the new Thread(runnable).start()
The call jettyServer.start() starts the server on its own thread (along with all of the other threads that the server needs.
For a basic example of junit and jetty ...
#Test
public void testGet() throws Exception
{
// Create Server
Server server = new Server(8080);
ServletContextHandler context = new ServletContextHandler();
ServletHolder defaultServ = new ServletHolder("default", DefaultServlet.class);
defaultServ.setInitParameter("resourceBase",System.getProperty("user.dir"));
defaultServ.setInitParameter("dirAllowed","true");
context.addServlet(defaultServ,"/");
server.setHandler(context);
// Start Server
server.start();
// Test GET
HttpURLConnection http = (HttpURLConnection)new URL("http://localhost:8080/").openConnection();
http.connect();
assertThat("Response Code", http.getResponseCode(), is(HttpStatus.OK_200));
// Stop Server
server.stop();
}
The #Before and #After junit annotations can also be used. This will start the server before each #Test and stop the server after.
package jetty;
import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;
import java.net.HttpURLConnection;
import java.net.URL;
import org.eclipse.jetty.http.HttpStatus;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.DefaultServlet;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class JUnitBeforeAfterJettyTest
{
private Server server;
#Before
public void startJetty() throws Exception
{
// Create Server
server = new Server(8080);
ServletContextHandler context = new ServletContextHandler();
ServletHolder defaultServ = new ServletHolder("default", DefaultServlet.class);
defaultServ.setInitParameter("resourceBase",System.getProperty("user.dir"));
defaultServ.setInitParameter("dirAllowed","true");
context.addServlet(defaultServ,"/");
server.setHandler(context);
// Start Server
server.start();
}
#After
public void stopJetty()
{
try
{
server.stop();
}
catch (Exception e)
{
e.printStackTrace();
}
}
#Test
public void testGet() throws Exception
{
// Test GET
HttpURLConnection http = (HttpURLConnection)new URL("http://localhost:8080/").openConnection();
http.connect();
assertThat("Response Code", http.getResponseCode(), is(HttpStatus.OK_200));
}
}
For the best approach, you can also use the #BeforeClass and #AfterClass techniques, along with auto-binding to an open port. This will only start the server once, per Test Class, run all of the #Test methods, then stop the server once at the end.
package jetty;
import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;
import java.net.HttpURLConnection;
import java.net.URI;
import java.net.URL;
import org.eclipse.jetty.http.HttpStatus;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.ServerConnector;
import org.eclipse.jetty.servlet.DefaultServlet;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;
import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;
public class JUnitBeforeAfterClassJettyTest
{
private static Server server;
private static URI serverUri;
#BeforeClass
public static void startJetty() throws Exception
{
// Create Server
server = new Server();
ServerConnector connector = new ServerConnector(server);
connector.setPort(0); // auto-bind to available port
server.addConnector(connector);
ServletContextHandler context = new ServletContextHandler();
ServletHolder defaultServ = new ServletHolder("default", DefaultServlet.class);
defaultServ.setInitParameter("resourceBase",System.getProperty("user.dir"));
defaultServ.setInitParameter("dirAllowed","true");
context.addServlet(defaultServ,"/");
server.setHandler(context);
// Start Server
server.start();
// Determine Base URI for Server
String host = connector.getHost();
if (host == null)
{
host = "localhost";
}
int port = connector.getLocalPort();
serverUri = new URI(String.format("http://%s:%d/",host,port));
}
#AfterClass
public static void stopJetty()
{
try
{
server.stop();
}
catch (Exception e)
{
e.printStackTrace();
}
}
#Test
public void testGet() throws Exception
{
// Test GET
HttpURLConnection http = (HttpURLConnection) serverUri.resolve("/").toURL().openConnection();
http.connect();
assertThat("Response Code", http.getResponseCode(), is(HttpStatus.OK_200));
}
}

change client and handler from DatagramPacket to POJO

I want to modify the client handler to use Foo instead of Datagram -- what changes are required in the client itself?
Surely it's not necessary to strictly keep to datagrams to send and receive with Netty? The Factorial example uses BigInteger, so, surely, it's possible to use POJO's.
Any and all attempts to create a class like:
class FooClientHandler extends SimpleChannelInboundHandler<Foo> are just non-starters for me, it literally won't send or receive with a server. (Yes, both client and server use similar handlers, generic classes with Foo.) So, I'm coming at this now from working code.
What's the key distinction between the factorial handler and the the datagram handler below? Or, is the primary distinction in how it's used in the client?
client:
package net.bounceme.dur.netty;
import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.DatagramPacket;
import io.netty.channel.socket.nio.NioDatagramChannel;
import io.netty.util.CharsetUtil;
import java.net.InetSocketAddress;
import java.util.logging.Logger;
import net.bounceme.dur.client.gui.MyProps;
public final class Client {
private static final Logger log = Logger.getLogger(Client.class.getName());
public void connect() throws InterruptedException {
MyProps p = new MyProps();
String host = p.getHost();
int port = p.getServerPort();
pingPongDatagram(host, port);
}
public void pingPongDatagram(String host, int port) throws InterruptedException {
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(group)
.channel(NioDatagramChannel.class)
.option(ChannelOption.SO_BROADCAST, true)
.handler(new DatagramClientHandler());
Channel ch = b.bind(0).sync().channel();
ch.writeAndFlush(new DatagramPacket(
Unpooled.copiedBuffer("QOTM?", CharsetUtil.UTF_8),
new InetSocketAddress(host, port))).sync();
log.info("wrote packet");
if (!ch.closeFuture().await(5000)) {
log.warning("server timed out");
}
} finally {
group.shutdownGracefully();
}
}
}
handler:
package net.bounceme.dur.netty;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.socket.DatagramPacket;
import io.netty.util.CharsetUtil;
import java.net.InetSocketAddress;
import java.util.logging.Logger;
public class DatagramClientHandler extends SimpleChannelInboundHandler<DatagramPacket> {
private static final Logger log = Logger.getLogger(DatagramClientHandler.class.getName());
#Override
public void channelRead0(ChannelHandlerContext ctx, DatagramPacket msg) throws Exception {
String response = msg.content().toString(CharsetUtil.UTF_8);
log.info(response);
DatagramPacket foo = new DatagramPacket(
Unpooled.copiedBuffer("QOTM?", CharsetUtil.UTF_8),
new InetSocketAddress("localhost", 4454));
ctx.writeAndFlush(foo);
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
log.severe(cause.toString());
ctx.close();
}
}
I omitted the server code, it's almost exactly as in the Ghandi quote example.
What changes do I need to make to the client so that the handler can use Foo instead of DatagramPacket?

All I can say with certainty is that this client:
package net.bounceme.dur.netty;
import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.Unpooled;
import io.netty.channel.Channel;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.DatagramPacket;
import io.netty.channel.socket.nio.NioDatagramChannel;
import io.netty.util.CharsetUtil;
import java.net.InetSocketAddress;
import java.util.logging.Logger;
import net.bounceme.dur.client.gui.MyProps;
import net.bounceme.dur.client.jdbc.Title;
public final class Client {
private static final Logger log = Logger.getLogger(Client.class.getName());
public void connect() throws InterruptedException {
MyProps p = new MyProps();
String host = p.getHost();
int port = p.getServerPort();
pingPongDatagram(host, port);
}
public void pingPongDatagram(String host, int port) throws InterruptedException {
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(group)
.channel(NioDatagramChannel.class)
.option(ChannelOption.SO_BROADCAST, true)
.handler(new TitleClientHandler());
Channel ch = b.bind(0).sync().channel();
ch.writeAndFlush(new DatagramPacket(
Unpooled.copiedBuffer("QOTM?", CharsetUtil.UTF_8),
new InetSocketAddress(host, port))).sync();
ch.writeAndFlush(new Title());
log.info("wrote packets");
if (!ch.closeFuture().await(5000)) {
log.warning("server timed out");
}
} finally {
group.shutdownGracefully();
}
}
}
and handler:
package net.bounceme.dur.netty;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import java.util.logging.Logger;
import net.bounceme.dur.client.jdbc.Title;
public class TitleClientHandler extends SimpleChannelInboundHandler<Title> {
private static final Logger log = Logger.getLogger(TitleClientHandler.class.getName());
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
log.severe(cause.toString());
ctx.close();
}
#Override
protected void channelRead0(ChannelHandlerContext chc, Title title) throws Exception {
log.info(title.toString());
}
}
don't, seemingly, communicate at all with the server -- even when the server has been modified accordingly.

netty DefaultChannelPipeline exceptionCaught

Unfortunately, I don't understand this output from the netty server:
BUILD SUCCESSFUL
Total time: 3 seconds
Jul 27, 2014 2:04:44 AM io.netty.handler.logging.LoggingHandler channelRegistered
INFO: [id: 0xcad25a31] REGISTERED
Jul 27, 2014 2:04:44 AM io.netty.handler.logging.LoggingHandler bind
INFO: [id: 0xcad25a31] BIND(0.0.0.0/0.0.0.0:4454)
Jul 27, 2014 2:04:44 AM io.netty.handler.logging.LoggingHandler channelActive
INFO: [id: 0xcad25a31, /0:0:0:0:0:0:0:0:4454] ACTIVE
Jul 27, 2014 2:04:59 AM io.netty.handler.logging.LoggingHandler logMessage
INFO: [id: 0xcad25a31, /0:0:0:0:0:0:0:0:4454] RECEIVED: [id: 0xff40b8a2, /127.0.0.1:37558 => /127.0.0.1:4454]
Jul 27, 2014 2:04:59 AM net.bounceme.dur.netty.ServerHandler <init>
INFO: starting..
Jul 27, 2014 2:04:59 AM io.netty.channel.DefaultChannelPipeline$TailContext exceptionCaught
WARNING: An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception.
io.netty.handler.codec.TooLongFrameException: Adjusted frame length exceeds 1048576: 2901213193 - discarded
at io.netty.handler.codec.LengthFieldBasedFrameDecoder.fail(LengthFieldBasedFrameDecoder.java:501)
at io.netty.handler.codec.LengthFieldBasedFrameDecoder.failIfNecessary(LengthFieldBasedFrameDecoder.java:477)
at io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(LengthFieldBasedFrameDecoder.java:403)
at io.netty.handler.codec.serialization.ObjectDecoder.decode(ObjectDecoder.java:68)
at io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(LengthFieldBasedFrameDecoder.java:343)
at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:241)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:149)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:319)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:787)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:125)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:116)
at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:137)
at java.lang.Thread.run(Thread.java:744)
^Cthufir#dur:~/NetBeansProjects/AgentServer$
thufir#dur:~/NetBeansProjects/AgentServer$
Presumably the netty-based server is complaining that it's receiving bad data in some respect?
client code:
package net.bounceme.dur.client.gui;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.util.logging.FileHandler;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.logging.SimpleFormatter;
import net.bounceme.dur.client.jdbc.Title;
public final class ApplicationDriver {
private static final Logger log = Logger.getLogger(ApplicationDriver.class.getName());
private TitlesGUI gui = null;
private Handler handler = null;
public ApplicationDriver() throws IOException, ClassNotFoundException {
handler = new FileHandler("application.log");
handler.setFormatter(new SimpleFormatter());
log.setLevel(Level.INFO);
log.addHandler(handler);
log.info("starting log..");
MyProps p = new MyProps();
String host = p.getHost();
int port = p.getServerPort();
guiThread();
readWrite(host, port);
}
private void guiThread() {
Thread g;
g = new Thread() {
#Override
public void run() {
try {
gui = new TitlesGUI();
} catch (IOException ex) {
log.severe(ex.toString());
}
gui.setVisible(true);
}
};
g.start();
}
public static void main(String... args) throws IOException, ClassNotFoundException {
new ApplicationDriver();
}
private void readWrite(final String host, final int port) throws IOException {
Thread inputOutput;
final Socket socket = new Socket(host, port);
inputOutput = new Thread() {
#Override
public void run() {
while (true) {
try (ObjectOutputStream objectOutputStream = new ObjectOutputStream(socket.getOutputStream());
ObjectInputStream objectInputStream = new ObjectInputStream(socket.getInputStream())) {
gui.setTitle((Title) objectInputStream.readObject());
Thread.sleep(1000);
} catch (IOException | ClassNotFoundException | InterruptedException ex) {
log.severe(ex.toString());
}
}
}
};
inputOutput.start();
}
}
is it a problem that the client is using regular sockets instead of netty? Both on the client and server side POJO's are being sent. (The Title class is serializable and the serialVersionUID values match up.)
a method from the GUI client (which is a bit large, it's a Netbeans Swing JFrame):
public void setTitle(Title title) {
this.title = title;
text.setText(title.toString());
}
the point of the above method is for something to send objects to the GUI, which is then updated accordingly. Similarly, I want to fire updates, or other-wise wire the GUI to socket i/o.
I don't really understand the output from the netty server. Is it a problem that the server uses netty while the client uses sockets? Both use the same POJO, with the serialVersionUID value. Here's the netty handler code:
package net.bounceme.dur.netty;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import java.util.logging.Logger;
import net.bounceme.dur.jdbc.Title;
public class ServerHandler extends SimpleChannelInboundHandler<Title> {
private static final Logger log = Logger.getLogger(ServerHandler.class.getName());
public ServerHandler() {
log.info("starting..");
}
#Override
public boolean acceptInboundMessage(Object msg) throws Exception {
log.info(msg.toString());
return true;
}
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
log.info(msg.toString());
ctx.write(new Title());
}
#Override
protected void channelRead0(ChannelHandlerContext chc, Title title) throws Exception {
log.info(title.toString());
chc.write(new Title());
}
}
Apparently, none of the server handler code is executed, as everything explodes immediately after the client connects.
server code:
package net.bounceme.dur.netty;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.codec.serialization.ClassResolvers;
import io.netty.handler.codec.serialization.ObjectDecoder;
import io.netty.handler.codec.serialization.ObjectEncoder;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import java.security.cert.CertificateException;
import java.util.logging.Logger;
import javax.net.ssl.SSLException;
public final class Server {
private static final Logger log = Logger.getLogger(Server.class.getName());
public static void main(String[] args) throws Exception {
MyProps p = new MyProps();
int port = p.getServerPort();
new Server().startServer(port, false);
}
private void startServer(int port, boolean ssl) throws CertificateException, SSLException, InterruptedException {
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline p = ch.pipeline();
p.addLast(
new ObjectEncoder(),
new ObjectDecoder(ClassResolvers.cacheDisabled(null)),
new ServerHandler());
}
});
b.bind(port).sync().channel().closeFuture().sync();
log.info("connected!");
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}

The TooLongFrameException raised by LengthFieldBasedFrameDecoder means one of the following:
The remote peer sent a very large message, which exceeds the limit. The default maximum length of a message is 1 MiB. If you expect to receive a message larger than that, specify an alternative maximum length when you construct a LengthFieldBasedFrameDecoder.
You passed wrong parameters to LengthFieldBasedFrameDecoder so that it is decoding a wrong place in your message. In this case, you'd better re-read the Javadoc of LengthFieldBasedFrameDecoder to specify the correct values for you.

Jboss Netty - Fails to send data continuously?

Using JBOSS Netty, I'm trying to send data continuously to the connected client. In the example below,
I try to send the time every 5 secs to the client, as soon as the client gets connected (channelConnected).
But this is not working. It works only if I comment the while loop.
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringEncoder;
public class SRNGServer {
public static void main(String[] args) throws Exception {
// Configure the server.
ServerBootstrap bootstrap = new ServerBootstrap(
new NioServerSocketChannelFactory(
Executors.newCachedThreadPool(),
Executors.newCachedThreadPool()));
// Configure the pipeline factory.
bootstrap.setPipelineFactory(new SRNGServerPipelineFactoryP());
// Bind and start to accept incoming connections.
bootstrap.bind(new InetSocketAddress(8080));
}
private static class SRNGServerHandlerP extends SimpleChannelUpstreamHandler {
private static final Logger logger = Logger.getLogger(SRNGServerHandlerP.class.getName());
#Override
public void channelConnected(
ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
// Send greeting for a new connection.
e.getChannel().write("Welcome to " + InetAddress.getLocalHost().getHostName() + "!\r\n");
while(true){
e.getChannel().write("It is " + new Date() + " now.\r\n");
Thread.sleep(1000*5);
}
}
#Override
public void exceptionCaught(
ChannelHandlerContext ctx, ExceptionEvent e) {
logger.log(
Level.WARNING,
"Unexpected exception from downstream.",
e.getCause());
e.getChannel().close();
}
}
private static class SRNGServerPipelineFactoryP implements ChannelPipelineFactory {
public ChannelPipeline getPipeline() throws Exception {
// Create a default pipeline implementation.
ChannelPipeline pipeline = Channels.pipeline();
pipeline.addLast("encoder", new StringEncoder());
pipeline.addLast("handler", new SRNGServerHandlerP());
return pipeline;
}
}
}

The Netty documentation actually states that you should never make a Handler wait because it might eventually deadlock. The reason is that handler methods are called directly by I/O threads. One I/O thread in Netty performs multiple I/O operations in a sequence, so it's not one thread per operation.
In the channelConnected method you should start a new thread with a reference to the channel and make that thread send the time every 5 seconds. This would spawn one thread per connection.
Alternatively, you can have one single thread looping over a list of clients every 5 seconds and sending the time to each of them in a sequence.
Anyway, it's important to use a different thread for sending than the one that calls the Handler.

For what its worth, I figured the solution and here's the working code. After the "write" of time, I register the future with my ChannelFuturelistener. And then from operationComplete I keep registering the new future for every write. This works for what I want to accomplish, without using any extra threads.
import java.net.InetSocketAddress;
import java.nio.channels.ClosedChannelException;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jboss.netty.bootstrap.ServerBootstrap;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ChannelPipelineFactory;
import org.jboss.netty.channel.ChannelStateEvent;
import org.jboss.netty.channel.Channels;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
import org.jboss.netty.channel.socket.nio.NioServerSocketChannelFactory;
import org.jboss.netty.handler.codec.string.StringEncoder;
public class SRNGServer {
public static void main(String[] args) throws Exception {
// Configure the server.
ServerBootstrap bootstrap = new ServerBootstrap(
new NioServerSocketChannelFactory(
Executors.newCachedThreadPool(),
//Executors.newCachedThreadPool()
Executors.newFixedThreadPool(2),2
));
// Configure the pipeline factory.
bootstrap.setPipelineFactory(new SRNGServerPipelineFactoryP());
// Bind and start to accept incoming connections.
bootstrap.bind(new InetSocketAddress(8080));
}
private static class SRNGServerHandlerP extends SimpleChannelUpstreamHandler {
private static final Logger logger = Logger.getLogger(SRNGServerHandlerP.class.getName());
#Override
public void channelConnected(
ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
// Send greeting for a new connection.
Channel ch=e.getChannel();
ChannelFuture writeFuture=e.getChannel().write("It is " + new Date() + " now.\r\n");
SRNGChannelFutureListener srngcfl=new SRNGChannelFutureListener();
writeFuture.addListener(srngcfl);
}
#Override
public void exceptionCaught(
ChannelHandlerContext ctx, ExceptionEvent e) {
logger.log(
Level.WARNING,
"Unexpected exception from downstream.",
e.getCause());
if(e.getCause() instanceof ClosedChannelException){
logger.log(Level.INFO, "****** Connection closed by client - Closing Channel");
}
e.getChannel().close();
}
}
private static class SRNGServerPipelineFactoryP implements ChannelPipelineFactory {
public ChannelPipeline getPipeline() throws Exception {
// Create a default pipeline implementation.
ChannelPipeline pipeline = Channels.pipeline();
pipeline.addLast("encoder", new StringEncoder());
pipeline.addLast("handler", new SRNGServerHandlerP());
return pipeline;
}
}
private static class SRNGChannelFutureListener implements ChannelFutureListener{
public void operationComplete(ChannelFuture future) throws InterruptedException{
Thread.sleep(1000*5);
Channel ch=future.getChannel();
if(ch!=null && ch.isConnected()){
ChannelFuture writeFuture=ch.write("It is " + new Date() + " now.\r\n");
//-- Add this instance as listener itself.
writeFuture.addListener(this);
}
}
}
}

Seems that the I/O thread is getting blocked as a result of sleep, so try using 2 worker threads instead:
ServerBootstrap bootstrap = new ServerBootstrap(
new NioServerSocketChannelFactory( Executors.newCachedThreadPool(),
Executors.newCachedThreadPool(), 2 ) );