How to detect a new incoming connection with Netty 4.0.x? - events

Question

How can I detect a new incoming connection with Netty 4.0.x?
Here is a code of a simple server:
public static void main(String[] args) {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup)
.channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
#Override
public void initChannel(SocketChannel ch) throws Exception {
System.out.println("Init channel");
ch.pipeline().addLast(new ChannelInboundHandlerAdapter() {
#Override
public void channelRegistered(ChannelHandlerContext ctx) {
System.out.println("Channel registered");
}
#Override
public void channelActive(final ChannelHandlerContext ctx) {
System.out.println("Channel active");
}
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
System.out.println("Channel read");
ctx.writeAndFlush((ByteBuf) msg);
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
System.out.println("Channel exception caught");
cause.printStackTrace();
ctx.close();
}
});
}
})
.option(ChannelOption.SO_BACKLOG, 128)
.childOption(ChannelOption.SO_KEEPALIVE, true);
ChannelFuture f;
try {
f = b.bind("127.0.0.1", 8080).sync();
f.channel().closeFuture().sync();
} catch (InterruptedException e) {
e.printStackTrace();
}
} finally {
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
The problem is that I can not detect a moment when a connection is established. All System.out.printlns are called only after the client sent some information to the server. And this means that the server can not send any data to the client before the client sent some data to the server.
What I expect:
server started
client started
client connected
{{ Init channel }}
{{ Channel registered }}
{{ Channel active }}
// Possibly send some data from server to client
Client send some data
{{ Channel read }}
What I get:
server started
client started
client connected
// Unable to send any data to client
Client send some data
{{ Init channel }}
{{ Channel registered }}
{{ Channel active }}
{{ Channel read }}
Are there any ways to achieve such behavior?

Answer 1

You can send some data when the client connect to server, so you can use the ctx.writeAndFlush(msg) in channelRegistered or channelActive method.
If your client does not receive any data, you should to ensure the type of Encode is right.

Answer 2

It looks like the port number 8080 caused somehow this problem. When I changed the port number to 12345 the program began to work as expected.