Send a String message from my Netty client to my server

Question

I have a Netty Client and a Netty Server, and after following the main tutorials in order to have an EchoClient / Server I wanted to make it so that my Client sends a message to my Server when he first connects to it.

Here are my ClientClassHandler 's methods that should take care of that:

 private final ByteBuf firstMessage;

    public ClientClassHandler() {
        firstMessage = Unpooled.buffer(ClientClass.SIZE);
        for (int i = 0; i < firstMessage.capacity(); i++) {
            firstMessage.writeByte((byte) i);
        }
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        System.out.println("Channel is active.");
        ctx.writeAndFlush(firstMessage);
    }

But as you can see the tutorial uses a ByteBuf and the use of a String does not seem to work !

Here is how I display my received message in my ServerClassHandler 's method:

@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
    System.out.println(msg); 
}

But when using a String for firstMessage and initializing it in the constructor and sending it, my Server does not display anything !

What did I not understand?

Answer 1

If you want to send a String then convert it into a ByteBuf first using Unpooled.copiedBuffer(string, charset)

Netty has a CharsetUtil to help with this

Answer 2

Just want add more info about String in netty ,

you can do convert Object into Bytebuff

 ByteBuf in = (ByteBuf) msg;
 String data = in.toString(CharsetUtil.UTF_8);

But if you have long String object I suggest using StringEncoder and decoder for netty and LineBasedFrameDecoder and extends you handler to

SimpleChannelInboundHandler<String>