@Override
            public long transferFrom(FileChannel fileChannel, long position, long count) throws IOException {
                return fileChannel.transferTo(position, count, channel);
            }
Sets the output channel to which messages received on this server are echoed.
This is useful in tests where the clients sending the messages don't receive
the responses (eg. testing graceful close).
clients/src/test/java/org/apache/kafka/common/network/NioEchoServer.java