Question

I need to receive full packet from other IP (navigation device) by TCP/IP.
The device has to send 966 bytes periodically (over one minute), for example.
In my case first received buffer has length 256 bytes (first piece of packet), the second is 710 bytes (last piece of packet), the third is full packet (966 bytes).
How to manual set minimal value for first received buffer length?

This is piece of my code:

Executor bossExecutors = Executors.newCachedThreadPool();
Executor workerExecutors = Executors.newCachedThreadPool();
NioServerSocketChannelFactory channelsFactory =
                new NioServerSocketChannelFactory(bossExecutors, workerExecutors);
ServerBootstrap bootstrap = new ServerBootstrap(channelsFactory);
ChannelPipelineFactory pipelineFactory = new NettyServerPipelineFactory(this.HWController);
bootstrap.setPipelineFactory(pipelineFactory);
bootstrap.setOption("child.tcpNoDelay", true);
bootstrap.setOption("child.keepAlive", true);
bootstrap.setOption("child.receiveBufferSizePredictorFactory", 
  new FixedReceiveBufferSizePredictorFactory(2048)
);
bootstrap.bind(new InetSocketAddress(this.port));

Answer 1

No matter what receiveBufferSizePredictorFactory you specify, you will see a message is split into multiple MessageEvents. It’s because TCP/IP is not a message-oriented protocol but a stream-oriented one. Please read the user guide that explains how to write a proper decoder that deals with this common issue.