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Netty server send a byte[] encoded by Protobuf, but C# client Socket.Receive keeps being 0

I am trying to accomplish an Unity game demo with network function, using C# for programming of client, and Java for server.
To be specific, server communication is implemented by Netty.
I also brought in Protobuf, which helps me define protocols of messages.
As I am new to server programming, dealing with packet merging and loss in TCP has not been considered in my code yet.
When I created sockets from client, and sent message to server, everything went well.
Problem happened when server replied:
In the client, an async method is ready to receive message. When I simply sent a string-format message from server, the method were able to get it.
But when I replaced the message with a 4-length byte[], which encoded from a Protobuf Message object, client just showed that it received NOTHING.
when I print what I've sent in the server console, it is like this:
00001000
00000001
00010000
00000001
My server code overrides channelRead and channelReadComplete functions of Netty.
In channelRead, ChannelHandlerContext.write was invoked to write the message to the transmission cache.
And in channelReadComplete, ChannelHandlerContext.flush was invoked, so that the message could be sent finally.
channelRead()
#Override
public void channelRead(ChannelHandlerContext ctx, Object msg) {
Request.MsgPack msgPack = (Request.MsgPack) msg;
Request.MsgPack.MsgType type = msgPack.getType();
switch (type)
{
case GetServerState:
final Request.GetServerState gssbody = msgPack.getGetServerState();
System.out.println("收到类型为" + type + "的消息，内容为：" +
"\nrequestId = " + gssbody.getRequestId()
);
byte[] bytes = ServerStateManager.getState(gssbody.getRequestId());
ctx.write(bytes);
break;
getState(): including Protobuf-encoding procedure
public static byte[] getState(int requestId)
{
ReturnServerState.Message.Builder replyBuilder = ReturnServerState.Message.newBuilder();
replyBuilder.setRequestId(requestId);
replyBuilder.setIsIdle(new ServerStateManager().isIdle());
return replyBuilder.build().toByteArray();
}
channelReadComplete()
#Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
try
{
ctx.flush();
}
finally
{
ctx.close();
}
}
Client code:
public class ShortLink
{
Socket clientSocket = null;
static byte[] result = new byte[1024];
Task ReceiveAsync<T>(string ip, int port)
{
return Task.Run(() =>
{
T component = default(T);
while (clientSocket.Receive(result) == 0)
{
break;
ReceiveAsync is invoked in the way of:
await ReceiveAsync<ReturnServerState>(ip, port);
when I found clientSocket.Receive(result) always output 0, I tried to log result[0], result[1], result[2], result[3] like this:
Debug.Log(Convert.ToString(result[0]) + ", " +
Convert.ToString(result[1]) + ", " +
Convert.ToString(result[2]) + ", " +
Convert.ToString(result[3]));
And the log turned to be 0,0,0,0.
I will be grateful for any idea of "why the client socket received nothing", and the solution.
Since I come from Asia, there may be a time lag between your reply and mine, and also English is not my mother tongue. However, I will try my best to reply in time.
Thanks a lot!

Okay..I have finally solve it myself
1.The usage "return replyBuilder.build().toByteArray()" is wrong because ProtoEncoder has already do toByteArray() for me:
public class ProtobufEncoder extends MessageToMessageEncoder<MessageLiteOrBuilder> {
public ProtobufEncoder() {
}
protected void encode(ChannelHandlerContext ctx, MessageLiteOrBuilder msg, List<Object> out) throws Exception {
if (msg instanceof MessageLite) {
out.add(Unpooled.wrappedBuffer(((MessageLite)msg).toByteArray()));
} else {
if (msg instanceof Builder) {
out.add(Unpooled.wrappedBuffer(((Builder)msg).build().toByteArray()));
}
}
}
}
So once I registered "new ProtobufEncoder()" in the Netty Channel Pipeline, I can just use "return replyBuilder.build()" - that is correct.
2.In "static byte[] result = new byte[1024];", The length of received message is defined casually, and it doesn't matter - until it really receives a message.
When receiving message, I shall always copy the message bytes to a new byte[] with a correct length firstly - or there will be just a 1024-length bytes[], with the data I need at the beginning, and several zeroes following, which will certainly fail to be decoded.

Library ZMQ for Java not work

I am trying to connect to a bitcoin node using the ZMQ library for Java. the problem is that when I try to receive a response the code remains frozen. Returns nothing.
This is my code:
public class CBETest {
private static final String TEST_URL = "obelisk.airbitz.co";
public static void main(String[] args) {
System.out.println("\t--- ZMQ ---");
Ctx c = zmq.ZMQ.createContext();
SocketBase s = c.createSocket(zmq.ZMQ.ZMQ_DEALER);
zmq.ZMQ.connect(s, "tcp://"+TEST_URL+":9091");
System.out.println("Connected!");
int sent = zmq.ZMQ.send(s, "blockchain.fetch_last_height", 0);
System.out.println("Sent: " + sent);
Msg msg = zmq.ZMQ.recv(s, 0);
System.out.println("Response " + Arrays.toString(msg.data()));
}
}
The code freezes in the line Msg msg = zmq.ZMQ.recv(s, 0);. I am using the calls described here for the full node implemetation. Thanks in advance!

The code is not freezing, it is blocking while waiting to receive a message.
I would suggest you put your above code in a thread/runnable class and use localhost as the TEST_URL and start the server.
Then create another Runnable class with a client that tries to connect to that port and send back a message and start that thread and see if the message gets through.
There is an example here:
http://zguide.zeromq.org/java:rtdealer

Websocket connection closed automatically?

I'm newbie to the web-socket programming...
I have the following JavaScript client code:
var connection = new WebSocket('ws://localhost:8080/OmegaThings/registerdevice');
connection.onopen = function () {
console.log("Socket has been opened state = " + connection.readyState);
connection.send('Ping'); // Send the message 'Ping' to the server
connection.send('Websocket client');
};
console.log("Socket has been opened state = " + connection.readyState);
connection.send('finish');
// Log errors
connection.onerror = function (error) {
console.log('WebSocket Error ' + error);
};
// Log messages from the server
connection.onmessage = function (e) {
console.log('Server: ' + e.data);
};
Java endpoint:
#ServerEndpoint("/registerdevice")
public class RegisterDeviceEndPoint
{
private static final Logger LOG = Logger.getLogger(RegisterDeviceEndPoint.class.getName());
#OnOpen
public void connectionOpened()
{
LOG.log(Level.INFO, "******************connection opened**************");
}
#OnMessage
public synchronized void processMessage(Session session, String message)
{
LOG.log(Level.INFO, "received message: {0}", message);
}
#OnClose
public void connectionClosed()
{
LOG.log(Level.INFO, "connection closed");
}
}
on the firefox console I got the following output:
"Socket has been opened state = 1"
InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable
"Socket has been opened state = 0"
on the GlassFish server log I got "ping" and "Websocket client", but the connection closed after onopen event exit(not sure), thus, the last word "finish" doesn't appear on the log and the error occurs.
I want to know if my code is correct?
What causes the error? javascript code, GlassFish server configuration or the java endpoint code?

Try to change the glassfish 8080 port, eg: 8887, or make sure Your antivirus/other application are not using port 80, I previously had experience where my server websocket was blocked by antivirus which using port 80.

How can we make producer in spring amqp rabbitmq waiting after sending all messages and release upon receiving all?

I am queuing all messages to rabbitmq queue and processing those on remote server. Below is my producer and reply handler in same class.
public class AmqpAsynchRpcItemWriter<T> implements ItemWriter<T>,
MessageListener {
protected String exchange;
protected String routingKey;
protected String queue;
protected String replyQueue;
protected RabbitTemplate template;
// Reply handler
#Override
public void onMessage(Message message) {
try {
String corrId = new String(message.getMessageProperties()
.getCorrelationId(), "UTF-8");
System.out.println("received " + corrId + " from " + this.replyQueue);
} catch (IOException e) {
e.printStackTrace();
}
}
//Producer
#Override
public void write(List<? extends T> items) throws Exception {
for (T item : items) {
System.out.println(item);
System.out.println("Queing " + item + " to " + this.queue);
Message message = MessageBuilder
.withBody(item.toString().getBytes())
.setContentType(MessageProperties.CONTENT_TYPE_TEXT_PLAIN)
.setReplyTo(this.replyQueue)
.setCorrelationId(item.toString().getBytes()).build();
template.send(this.exchange, this.routingKey, message);
System.out.println("Queued " + item + " to " + this.queue);
}
// It should wait here untill we get all replies in onMessage, How can we do this ?
}
I am sending all messages in write method and getting replies in onMessage. This is working properly but write doesnt wait for replies, it returns to caller and spring-batch step is marked completed.
But I want the process to wait for replies after sending all message till we get all replies in onMessage. How can we do this ?

You can use any number of synchronization techniques; for example have the listener put the replies in a LinkedBlockingQueue and have the sender take (or poll with timeout) from the queue until all the replies are received.
Or, don't use a listener at all and simply use the same RabbitTemplate to receive() from the reply queue until all the replies are received.
However, receive() returns null if the queue is empty so you'll have to sleep between receives to avoid spinning the CPU.

Not able to receive ACLMessage in android via JADE

I'm currently using Topic based communication using JADE. I'm able to register a JADE agent using jade.core.messaging.TopicManagementFEService thereby connecting to the main-container in the same platform.
The details are below:
Main-Container: a simple LAMP/WAMP Server that hosts the Main-Container.
Client: An Android Emulator(testing purpose) to connect to the main-container.
Currently,
Server starts the main-container
Android emulator connects to the Main-container successfully (Agent created along with Topic Mgmt Service enabled)
Server is sending messages based on a specific topic.
But my Android Client is not able to receive this message although the topic registered is the same on both ends!
You can see the code below:
Server Side:
TopicManagementHelper topicHelper = (TopicManagementHelper) getHelper(TopicManagementHelper.SERVICE_NAME);
final AID sensorTopic = topicHelper.createTopic("JADE");
topicHelper.register(sensorTopic);
addBehaviour(new TickerBehaviour(this, TIMER_VALUE_IN_MILLISECONDS) {
private static final long serialVersionUID = -2567778187494378326L;
public void onTick() {
ACLMessage msg = new ACLMessage(ACLMessage.INFORM);
msg.addReceiver(eventTopic);
msg.setContent(eventValue);
myAgent.send(msg);
}
});
Android Side:
// Registering on Android Side as well
TopicManagementHelper topicHelper = (TopicManagementHelper) getHelper(TopicManagementHelper.SERVICE_NAME);
topic = topicHelper.createTopic("JADE"); // See, same topic!
topicHelper.register(topic);
behaviour = new myBehaviour(this, TIMER_VALUE_IN_MILLISECONDS, topic);
addBehaviour(behaviour);
private class myBehaviour extends TickerBehaviour {
private static final long serialVersionUID = 4782913834042415090L;
AID topic;
Agent agent;
MessageTemplate tpl;
public myBehaviour(Agent a, long period, AID topic) {
super(a, period);
this.agent = a;
this.topic = topic;
}
public void onTick() {
tpl = MessageTemplate.MatchTopic(topic);
ACLMessage msg = receive(tpl);
if (msg != null) {
logger.log(Level.INFO, "Agent "+ agent.getLocalName() +
": Message about topic "+ topic.getLocalName() +" received. \n" +
"Content is " + msg.getContent());
data = msg.getContent();
} else {
logger.log(Level.INFO, "In here..."); // Always executes only this code!
block();
}
}
}
Where am I going wrong here? It always executes the else part in the Android side which is obvious to say that message received is NULL!

Never mind. The logic was wrong. The Android-Agent was not identifying itself to the Central-Agent.
I set the Ontology so that the Central Agent is able to identify such message and sends the message accordingly. Now, it is receiving messages!
Self-help works sometimes! ;-)

Receiving topic messages doesn't work correctly with Android up to version 4.3.0 in JADE. Android can send out topic messages but can't receive them. I found this out through my own issues. I've posted more info about it in my own question on stack overflow.
Take a look. JADE Leap Android App unable to receive topic messages