Essentially, you would need to maintain a "register" of handlers, I guess,
and at some point, instruct them to perform a write operation.
e.g. in your ChannelInitializer, don't simply do
channel.pipeline().addLast("myHandler", new MyHandler());
, rather keep a reference to it in an accessible structure (e.g. List, Map,
whatever).
e.g.
Pass the (initially empty) list of handlers in to the constructor of your
initializer, and save it as an instance variable, then in the initChannel()
method:
MyHandler h = new MyHandler();
handlers.add(h);
channel.pipeline().addLast("myHandler", h);
Then you can look up the Handler when you want to instruct it to write
something.
You'd want to add locking and concurrency protection to the list, of
course, and make sure that the list of MyHandler also gets updated when a
connection is closed. No point in keeping them hanging around, and it would
likely stop garbage collection.
Rogan
On Mon, Sep 5, 2016 at 3:03 PM L_DisplayName <[email protected]>
wrote:
> Thank you Rogan for your response, I appreciate it. I am also interested
> in knowing (implementation/coding) wise, how I can access, write to and
> manage a group of channels outside of the handler class.
>
> Thank you!
>
> On Monday, September 5, 2016 at 8:09:18 AM UTC-4, L_DisplayName wrote:
>>
>> Greetings All,
>> I wanted to know how can I manage a group of channels outside of a
>> server's channel handler? I am implementing a file server and I want the
>> server to be able to transfer files through parallel data channels once it
>> receives a file request from a client. For example, if I have a single 4GB
>> file and 4 data channels/connections, I want the server to transfer 1GB
>> through each of the data channels simultaneously (note files are divided
>> evenly among all data channels). In essence, the server receives and
>> processes the file request through one of the channel's channelHandler -
>> channelRead method, but then how can I inform and have each channel send
>> their part/portion of the file?
>>
>> For example, if I have a simple FileServerHandler class as below for each
>> of the 4 channels, and I wanted to know how can I inform and have each
>> channel send their part/portion of the file.
>>
>> public class FileServerHandler extends SimpleChannelInboundHandler<
>> ByteBuf> {
>>
>> private Logger logger; private String currentFileName;
>> private String currentDirectory;
>> private long currentFileOffset;
>> private long currentFileChunkSize;
>> private boolean isDirectory;
>>
>>
>> public FileServerHandler() {
>>
>> logger = Logger.getLogger(this.getClass().getName());
>>
>> }
>>
>> public void channelActive(ChannelHandlerContext ctx) throws Exception{
>>
>> logger.info("Server:channel is active ");
>>
>> }
>>
>>
>> @Override
>> public void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) throws
>> Exception {
>> logger.info("Server:channelRead0: filePath = " + msg);
>> processFileRequest(msg); //Obtains the file or directory to retrieve
>> and the size of the file or
>> //files within a directory to retrieve recursively
>>
>> /*
>> *At this point I wish to tell the other channels the file or directory
>> to retrieve, the file size, and the portion of the file(s) it should send?
>> How can I do this? Also, if I implemented a channelManager, How can I pass
>> this information to the channelManager and have it write the data to each
>> channel?*
>> */
>>
>> }
>>
>> @Override
>> public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
>> {
>> cause.printStackTrace();
>>
>> if (ctx.channel().isActive()) {
>> ctx.writeAndFlush("ERR: " +
>> cause.getClass().getSimpleName() + ": " +
>> cause.getMessage() + '\n').addListener(ChannelFutureListener.CLOSE);
>> }
>> }
>> }
>>
>>
>>
>>
>>
>> --
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