Question

I am writing an application to send small file (~2kb) from Netty server to client through WebSocket.

For testing whether the file send success, I had the follows test.

1. A client connect to server.
2. Setting to drop all packets from server on the client machine.
3. The server send a file to the client.
4. Checking the result of “ChannelFuture” on the server.

I got true from “future.isSuccess()” and “future.isDone()” immediately when I send a file with ~2kb in this test even client side cannot receive the file.

I repeated this test for files with larger size. I find out that if the file size is larger than ~7kb, the “ChannelFuture future” will wait the feedback from transmission. This is the result I expected.

I am using Netty3.6.1 and my application is built base on “org.jboss.netty.example.http.websocketx.server”.

Here is part of my code:

ChannelBuffer cb = ChannelBuffers.copiedBuffer(myfile_byteArray);   
ChannelFuture result = ctx.getChannel().write( new BinaryWebSocketFrame( cb ) );
result.addListener(new ChannelFutureListener() {
            public void operationComplete(ChannelFuture future) throws Exception {
                if (future.isSuccess()){  
                    System.err.println("future.isSuccess()");  
                }  
                if (future.isDone()){  
                    System.err.println("future.isDone()");  
                }  
                if (future.isCancelled()){  
                    System.err.println("future.isCancelled()");  
                }  
            }
        });

Does anyone know how could I having “ChannelFuture” work correctly for file with small file size?

Many thanks in advance!

Answer 1

ChannelFuture will only be notified if the data can be written out to the remote peer. So if it is notified then the other peer received the data without a problem. This is true for all sizes of data.