TCP and UDP on the same port and suggestions for CodecFilter vs IoHandler thread models

[Michael Mealling]

I'm implementing a DNS server using MINA (yes, I've looked at the one in 
the directory project but no insight from that one since it only binds 
to UDP). DNS servers should listen on both TCP and UDP (and in this case 
it is required since some of the answers will blow out the UDP size 
limits). Anyway, I'm having two problems;

1) Just to get the skeleton working I wanted to re-create the 
ReverseProtocol example so that it worked on both UDP and TCP on the 
same port. I have it binding and the logger shows the connections and 
the packet contents but the ReverseProtocolHandler never sees the 
packet. I've included the main class below. I haven't really modified 
ReverseProtocolHandler from the example other than changing the package 
name.

2) Conceptually I'm trying to wrap my head around how to connect the 
session oriented TCP side and the non-session oriented datagram side 
together in the CodecFilter so that the IoHandler just gets a DNS 
question that it simply answers without regard to whether it was 
received via TCP or UDP. Does anyone have any suggestions for how to 
handle that within the CodecFilter? One of the things I'm really 
confused by is the use of Session 'language' about the DatagramAcceptor 
and what that means.

Thanks!

public class DnsServer {
    private static final int PORT = 5300;
    public static void main( String[] args ) throws Exception
    {
        IoAcceptor tcpacceptor = new SocketAcceptor();
        IoAcceptor udpacceptor = new DatagramAcceptor();

        // Prepare the configuration
        SocketAcceptorConfig tcpcfg = new SocketAcceptorConfig();
        DatagramAcceptorConfig udpcfg = new DatagramAcceptorConfig();
        LoggingFilter loggingfilter = new LoggingFilter();
        tcpcfg.setReuseAddress( true );
        tcpcfg.getFilterChain().addLast( "logger", loggingfilter );
        ProtocolCodecFilter codecFilter = new ProtocolCodecFilter(
                new  TextLineCodecFactory(Charset.forName("UTF-8")));

        tcpcfg.getFilterChain().addLast(
                "codec",
                codecFilter);

        udpcfg.getFilterChain().addLast( "logger", loggingfilter);
        udpcfg.getFilterChain().addLast("codec", codecFilter);

        // Bind
        tcpacceptor.bind(
                new InetSocketAddress( PORT ),
                new ReverseProtocolHandler(),
                tcpcfg );

        udpacceptor.bind(
                        new InetSocketAddress( PORT ),
                        new ReverseProtocolHandler(),
                        udpcfg);

        System.out.println( "Listening on port " + PORT );
    }
}

--
Michael Mealling                         Refactored Networks, LLC
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