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
Related
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.
I have configured one xbee pro as coordinator (API mode) and other as router (API mode). I trying to send data from coordinator to router using xbee java api, but in the router code i keep getting null, am I doing something wrong.
Below is the code for Sending data (coordinator):
public class MainApp {
private static final String PORT = "/dev/ttyUSB0";
private static final int BAUDRATE = 9600;
public static void main(String[] args)
{
String data = "Helloww";
XBeeDevice mycord = new XBeeDevice(PORT, BAUDRATE);
try {
mycord.open();
System.out.println("Port is opened\n");
System.out.println("remote device connection\n");
//mac of my router
RemoteXBeeDevice router = new RemoteXBeeDevice(mycord,
new XBee64BitAddress("0013A20040DD9BDD"));
System.out.println("Sending data\n");
mycord.sendData(router, data.getBytes());
} catch (XBeeException e) {
e.printStackTrace();
mycord.close();
System.exit(1);
}
}
}
code on router side
public class RecvApp {
private static final String PORT = "/dev/ttyUSB1";
private static final int BAUDRATE = 9600;
public static void main(String[] args)
{
XBeeDevice myrouter = new XBeeDevice(PORT, BAUDRATE);
try {
myrouter.open();
System.out.println("router port opened\n");
//mac of coordinator
RemoteXBeeDevice remotecord = new RemoteXBeeDevice(myrouter, new XBee64BitAddress("0013A20040D96FE5"));
XBeeMessage msg = myrouter.readDataFrom(remotecord);
System.out.print(msg);
} catch (XBeeException e) {
// TODO Auto-generated catch block
e.printStackTrace();
myrouter.close();
System.exit(1);
}
}
}
On the router you need to have a loop that checks for messages and prints them out. The API should have a method you can call to check for messages before calling readDataFrom() (or maybe you just ignore the null response). Sleep for a few milliseconds between each check. Right now, there isn't much opportunity for your message to come through before the program quits.
When debugging something like this, start by isolating your problem. Which side is failing, the coordinator or the router? Are you sure the XBee modules have joined to each other and are on the same network?
One test would be to run a simple terminal emulator on the serial port connected to the router, do you see any frames coming through? If you look at a hex dump of the bytes, do you see your "Helloww" message? If not, you need to get the coordinator working first before you debug your router.
Found the issue, I was not converting the message received in the correct format. Added the below lines
String content = HexUtils.prettyHexString(HexUtils.byteArrayToHexString(xbeeMessage.getData()));
System.out.println("Hex data" + "" + content + "\n");
String value = new String(xbeeMessage.getData());
System.out.print("Actual msg" + " " + value + "\n");
Works now :)
Good morning, I have the following code:
int numero = 22492;
String PhnNoStr = String.valueOf (numero);
String transaction = WriteText(tipoTransacao);
String SmsStr = "ECART" + "" + transaction + idToken;
System.out.println ("Message:" + smsStr);
MessageConnection msgCon = null;
msgCon = (MessageConnection) Connector.open ("sms :/ /" + + phnNoStr ": 500");
TextMessage TxtMsg = (TextMessage) msgCon.newMessage (MessageConnection.TEXT_MESSAGE);
txtMsg.setPayloadText (smsStr);
msgCon.send (TxtMsg);
so I send that message by default it returns me a message. I can send and receive this message, however I need to intercept when I receive this message, does anyone know how I can do this?
Thank you
You can use PushRegistry to have your midlet launched when a SMS is received and midlet is not running.
PushRegistry.registerConnection("sms://:500", "your_package.Your_MIDlet", "*");
To handle incoming SMS, you need to open connection and listen for incoming message, eg:
class SMSHandler implements MessageListener, Runnable {
public void start() {
...
connection = (MessageConnection) Connector.open("sms://:500", Connector.READ);
connection.setMessageListener(this);
}
public void notifyIncomingMessage(MessageConnection messageConnection) {
(new Thread(this)).start();
}
public void run() {
final Message message = connection.receive();
...
}
(The reason for processing the message in another thread is that blocking I/O should not be done in system callback - at least WTK emulator will print warning, and on some phones midlet will just freeze).
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
please excuse my writing errors...
I'm using NetBeans to run a homemade server and a client, and it all works fine. As I said before, I'm using "Socket" on my client, and "ServerSocket" on my sv. I'm also using JDBC Mysql in the server.
The problem starts when I generate both java files in their distributable folders and use them. The client sends information to the server (it starts with .getOutputStream() and .getInputStream(), then .flush() ), but the server doesn't receive any message. I tried seeing where it stops and it's in
clients[i] = new Client (server.accept(), i);
The crazy thing happens when I try executing my server from NetBeans and the client from my desktop... It works! So the server must be the problem. I'm also using an opened UDP port, and i'm looking for the IP of the server on 192.168.0.10 (which is my computer, in LAN).
I hope someone can help me, thanks in advance!
Here I paste my code, i'm sorry some variables are in spanish:
public ServidorMultiCliente() {
super("Servidor MultiCliente");
initComponents();
try{
servidor = new ServerSocket( 500, maxNumberClients);
}catch(IOException excepcion){
excepcion.printStackTrace();
System.exit(1);
}
serverWriteBox.append("Server iniciated, waiting for connections..."); }
I run these, from the Server:
public void ejecutar(){
clientsAcceptor.start();
messagesListener.start(); }
Where clientsAcceptor is:
private class aceptadorClientes extends Thread{
public void run(){
for( int i = 1; i < maxNumberClients; i++ ){
try{
clientes[i] = new Cliente (servidor.accept(), i); // **Here it stops**
// It never reaches here... (without using NetBeans)
clientes[i].start();
clientes[i].aceptado = true;
}catch(IOException excepcion){
excepcion.printStackTrace();
}
}
That's how I accept clients in different threads. I make the same thing with messageListener, which is a new thread for every new client. It's in a loop, always listening. And here I paste my executable Client, which is different from the Cliente class I was using in ServidorMultiCliente:
public Cliente(){
}
public Cliente(String host){
this.host = host;
this.executeConnection();
}
public void executeConnection(){
int connect = 0;
try {
cliente = new Socket(InetAddress.getByName(host), 500);
conectar = 1;
} catch (IOException ex) {
conectar = 0;
this.ejecutarConexion();
}
if(conectar == 1){
obtainFlows();
}
}
private void obtainFlows(){
try{
output= new ObjectOutputStream( cliente.getOutputStream());
output.flush(); // Here I should be "connected"
input = new ObjectInputStream(cliente.getInputStream());
} catch(IOException ex){
this.initiateDisconnection();
}
sendFlows("I'm connected!");
new messageListener().start(); // This is a thread
}
ServerSocket#accept is a blocking call. It listens to a port and returns a Socket when a client connects. You don't show very much of your server logic but it seems you put clients in an array so you obviously want to support more than one client. You don't show if your Client class starts a thread and returns immediatly.
You should have a server loop that just listens to a server socket and creates clients after it retrieved a client socket. Even if you do this in your Client constructor (I can't tell without the code) it is not a very good place for this and seriously hinders debugging.
If you don't start threads for your clients this would explain a server that "stops" (if "stops" means "blocks" and not "crashes"). See "Writing the Server Side of a Socket" in the Java Tutorial for a detailed explanation.
I can't think of why it behaves different when started via Netbeans. A little bit more of code context is needed.