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I'm trying to communicate with a server that uses DataInputStream.readUTF and DataOutputStream.writeUTF.

I did the usual bootstrapping code to setup my client, and set the following pipelinefactory

    bootstrap.setPipelineFactory(new ChannelPipelineFactory() {

        @Override
        public ChannelPipeline getPipeline() throws Exception {
            return Channels.pipeline(
                    new LengthFieldBasedFrameDecoder(65536, 0, 2),
                    new StringDecoder(CharsetUtil.UTF_8),
                    new StringEncoder(CharsetUtil.UTF_8),
                    new MyClientHandler());
        }
    });

in MyClientHandler which extends SimpleChannelUpstreamHandler, I have the following:

    boolean sent = false; //is this thread safe?

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
        logger.log(Level.INFO, e.getMessage().toString());
        e.getChannel().write("Hello over there!");

        if(!sent){
             //do something and set sent
        }
    }

I managed to receive messages from server successfully, but server is not receiving my "hello over there" message. Not sure what I might have overlooked.

Also, notice the boolean sent, can I add such fields and work with them without threading concerns?

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1 回答 1

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  • 我成功地从服务器接收消息，但服务器没有收到我的“你好”消息。不知道我可能忽略了什么。

因为可以使用 LengthFieldBasedFrameDecoder 接收来自服务器的消息，所以消息具有长度字段。

 +--------+----------+
 | Length | Message  |
 +--------+----------+

因此，服务器有可能期望接收到的消息具有长度字段。如果长度字段是这样写的呢？

 +--------+---------------------+
 | 0x0011 | "Hello over there!" |
 +--------+---------------------+

[样本]

@Override
public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {
    logger.log(Level.INFO, e.getMessage().toString());
    byte[] message = "Hello over there!".getBytes("UTF-8");

    ChannelBuffer buf = ChannelBuffers.buffer(message.length + 2);
    buf.clear();
    short len = (short)message.length;
    buf.writeShort(len);
    buf.writeBytes(message);
    e.getChannel().write(buf);

    if(!sent){
        //do something and set sent
    }
}
  • 另外，请注意发送的布尔值，我可以添加这些字段并使用它们而不用担心线程问题吗？

是的，您可以添加字段来存储一些状态。而且你不需要考虑线程的同步。

于 2011-02-09T04:02:14.143 回答