netty SimpleChannelInboundHandler<String> channelRead0 only occasionally invoked - sockets

Question

I know that there are several similar questions that have either been answered or still outstanding, however, for the life of me...
Later Edit 2016-08-25 10:05 CST - Actually, I asked the wrong question.
The question is the following: given that I have both a netty server (taken from DiscardServer example) and a netty client - (see above) what must I do to force the DiscardServer to immediately send the client a request?
I have added an OutboundHandler to the server and to the client.
After looking at both the DiscardServer and PingPongServer examples, there is an external event occurring to kick off all the action. In the case of Discard server, it is originally waiting for a telnet connection, then will transmit whatever was in the telnet msg to the client.
In the case of PingPongServer, the SERVER is waiting on the client to initiate action.
What I want is for the Server to immediately start transmitting after connection with the client. None of the examples from netty seem to do this.
If I have missed something, and someone can point it out, much good karma.
My client:
public final class P4Listener {
static final Logger LOG;
static final String HOST;
static final int PORT;
static final Boolean SSL = Boolean.FALSE;
public static Dto DTO;
static {
LOG = LoggerFactory.getLogger(P4Listener.class);
HOST = P4ListenerProperties.getP4ServerAddress();
PORT = Integer.valueOf(P4ListenerProperties.getListenerPort());
DTO = new Dto();
}
public static String getId() { return DTO.getId(); }
public static void main(String[] args) throws Exception {
final SslContext sslCtx;
if (SSL) {
LOG.info("{} creating SslContext", getId());
sslCtx = SslContextBuilder.forClient().trustManager(InsecureTrustManagerFactory.INSTANCE).build();
} else {
sslCtx = null;
}
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(group).channel(NioSocketChannel.class)
.handler(new LoggingHandler(LogLevel.INFO))
.handler(new P4ListenerInitializer(sslCtx));
// Start the connection attempt.
LOG.debug(" {} starting connection attempt...", getId());
Channel ch = b.connect(HOST, PORT).sync().channel();
// ChannelFuture localWriteFuture = ch.writeAndFlush("ready\n");
// localWriteFuture.sync();
} finally {
group.shutdownGracefully();
}
}
}
public class P4ListenerHandler extends SimpleChannelInboundHandler<String> {
static final Logger LOG = LoggerFactory.getLogger(P4ListenerHandler.class);
static final DateTimeFormatter DTFormatter = DateTimeFormatter.ofPattern("yyyyMMdd-HHMMss.SSS");
static final String EndSOT;
static final String StartSOT;
static final String EOL = "\n";
static final ClassPathXmlApplicationContext AppContext;
static {
EndSOT = P4ListenerProperties.getEndSOT();
StartSOT = P4ListenerProperties.getStartSOT();
AppContext = new ClassPathXmlApplicationContext(new String[] { "applicationContext.xml" });
}
private final RequestValidator rv = new RequestValidator();
private JAXBContext jaxbContext = null;
private Unmarshaller jaxbUnmarshaller = null;
private boolean initialized = false;
private Dto dto;
public P4ListenerHandler() {
dto = new Dto();
}
public Dto getDto() { return dto; }
public String getId() { return getDto().getId(); }
Message convertXmlToMessage(String xml) {
if (xml == null)
throw new IllegalArgumentException("xml message is null!");
try {
jaxbContext = JAXBContext.newInstance(p4.model.xml.request.Message.class, p4.model.xml.request.Header.class,
p4.model.xml.request.Claims.class, p4.model.xml.request.Insurance.class,
p4.model.xml.request.Body.class, p4.model.xml.request.Prescriber.class,
p4.model.xml.request.PriorAuthorization.class,
p4.model.xml.request.PriorAuthorizationSupportingDocumentation.class);
jaxbUnmarshaller = jaxbContext.createUnmarshaller();
StringReader strReader = new StringReader(xml);
Message m = (Message) jaxbUnmarshaller.unmarshal(strReader);
return m;
} catch (JAXBException jaxbe) {
String error = StacktraceUtil.getCustomStackTrace(jaxbe);
LOG.error(error);
throw new P4XMLUnmarshalException("Problems when attempting to unmarshal transmission string: \n" + xml,
jaxbe);
}
}
#Override
public void channelActive(ChannelHandlerContext ctx) {
LOG.debug("{} let server know we are ready", getId());
ctx.writeAndFlush("Ready...\n");
}
/**
* Important - this method will be renamed to
* <code><b>messageReceived(ChannelHandlerContext, I)</b></code> in netty 5.0
*
* #param ctx
* #param msg
*/
#Override
protected void channelRead0(ChannelHandlerContext ctx, String msg) throws Exception {
ChannelFuture lastWriteFuture = null;
LOG.debug("{} -- received message: {}", getId(), msg);
Channel channel = ctx.channel();
Message m = null;
try {
if (msg instanceof String && msg.length() > 0) {
m = convertXmlToMessage(msg);
m.setMessageStr(msg);
dto.setRequestMsg(m);
LOG.info("{}: received TIMESTAMP: {}", dto.getId(), LocalDateTime.now().format(DTFormatter));
LOG.debug("{}: received from server: {}", dto.getId(), msg);
/*
* theoretically we have a complete P4(XML) request
*/
final List<RequestFieldError> errorList = rv.validateMessage(m);
if (!errorList.isEmpty()) {
for (RequestFieldError fe : errorList) {
lastWriteFuture = channel.writeAndFlush(fe.toString().concat(EOL));
}
}
/*
* Create DBHandler with message, messageStr, clientIp to get
* dbResponse
*/
InetSocketAddress socketAddress = (InetSocketAddress) channel.remoteAddress();
InetAddress inetaddress = socketAddress.getAddress();
String clientIp = inetaddress.getHostAddress();
/*
* I know - bad form to ask the ApplicationContext for the
* bean... BUT ...lack of time turns angels into demons
*/
final P4DbRequestHandler dbHandler = (P4DbRequestHandler) AppContext.getBean("dbRequestHandler");
// must set the requestDTO for the dbHandler!
dbHandler.setClientIp(clientIp);
dbHandler.setRequestDTO(dto);
//
// build database request and receive response (string)
String dbResponse = dbHandler.submitDbRequest();
/*
* create ResponseHandler and get back response string
*/
P4ResponseHandler responseHandler = new P4ResponseHandler(dto, dbHandler);
String responseStr = responseHandler.decodeDbServiceResponse(dbResponse);
/*
* write response string to output and repeat exercise
*/
LOG.debug("{} -- response to be written back to server:\n {}", dto.getId(), responseStr);
lastWriteFuture = channel.writeAndFlush(responseStr.concat(EOL));
//
LOG.info("{}: response sent TIMESTAMP: {}", dto.getId(), LocalDateTime.now().format(DTFormatter));
} else {
throw new P4EventException(dto.getId() + " -- Message received is not a String");
}
processWriteFutures(lastWriteFuture);
} catch (Throwable t) {
String tError = StacktraceUtil.getCustomStackTrace(t);
LOG.error(tError);
} finally {
if (lastWriteFuture != null) {
lastWriteFuture.sync();
}
}
}
private void processWriteFutures(ChannelFuture writeFuture) throws InterruptedException {
// Wait until all messages are flushed before closing the channel.
if (writeFuture != null) {
writeFuture.sync();
}
}
#Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
/**
* Creates a newly configured {#link ChannelPipeline} for a new channel.
*/
public class P4ListenerInitializer extends ChannelInitializer<SocketChannel> {
private static final StringDecoder DECODER = new StringDecoder();
private static final StringEncoder ENCODER = new StringEncoder();
private final SslContext sslCtx;
public P4ListenerInitializer(SslContext sslCtx) {
this.sslCtx = sslCtx;
}
#Override
public void initChannel(SocketChannel ch) {
P4ListenerHandler lh = null;
ChannelPipeline pipeline = ch.pipeline();
if (sslCtx != null) {
P4Listener.LOG.info("{} -- constructing SslContext new handler ", P4Listener.getId());
pipeline.addLast(sslCtx.newHandler(ch.alloc(), P4Listener.HOST, P4Listener.PORT));
} else {
P4Listener.LOG.info("{} -- SslContext null; bypassing adding sslCtx.newHandler(ch.alloc(), P4Listener.HOST, P4Listener.PORT) ", P4Listener.getId());
}
// Add the text line codec combination first,
pipeline.addLast(new DelimiterBasedFrameDecoder(8192, Delimiters.lineDelimiter()));
pipeline.addLast(DECODER);
P4Listener.LOG.debug("{} -- added Decoder ", P4Listener.getId());
pipeline.addLast(ENCODER);
P4Listener.LOG.debug("{} -- added Encoder ", P4Listener.getId());
// and then business logic.
pipeline.addLast(lh = new P4ListenerHandler());
P4Listener.LOG.debug("{} -- added P4ListenerHandler: {} ", P4Listener.getId(), lh.getClass().getSimpleName());
}
}
#Sharable
public class P4ListenerOutboundHandler extends ChannelOutboundHandlerAdapter {
static final Logger LOG = LoggerFactory.getLogger(P4ListenerOutboundHandler.class);
private Dto outBoundDTO = new Dto();
public String getId() {return this.outBoundDTO.getId(); }
#Override
public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
try {
ChannelFuture lastWrite = ctx.write(Unpooled.copiedBuffer((String) msg, CharsetUtil.UTF_8));
try {
if (lastWrite != null) {
lastWrite.sync();
promise.setSuccess();
}
} catch (InterruptedException e) {
promise.setFailure(e);
e.printStackTrace();
}
} finally {
ReferenceCountUtil.release(msg);
}
}
}
output from client

Answer 1

Just override channelActive(...) on the handler of the server and trigger a write there.