Netty - can not write to channel at registration (channelRegistered event)

Question

I've encountered a problem concerning sending packets at channel registration (Client -> Server). To test furthermore, if I send the packet after the registration, I am allowed to send the packet. The opposite way (Server -> Client) works totally fine. Registration function:

@Override
public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
    ctx.channel().write(new byte[] {0x00});
}

It also encounters an encoder down the filter chain:

public class Encoder extends MessageToByteEncoder<byte[]>{

@Override
protected void encode(ChannelHandlerContext ctx, byte[] b, ByteBuf bb) throws Exception {
    byte[] data = b.getData();

    bb.writeInt(data.length);
    bb.writeBytes(data);
}
}

The server therefore does not receive the aforementioned packet - as a result, I debugged to see if channelRead event fired and it did not. (Neither did my decode class to decode the data)

Any assumptions ?

Answer 1

channelRegistered is called when the channel is registered to it's EventLoop. That does not imply it is ready to send data yet, the channel hasn't even opened a socket yet. You want channelActive, which is called when the channel is active, i.e. ready to send and receive data.