My project uses mqtt for notifications. And need real time notification.
I have mqtt class like this
class Mqtt {
...
Mqtt._() {
mqttClient = MqttServerClient.withPort(server, clientIdentifier, port);
///Successful connection callback
mqttClient.onConnected = _onConnected;
///Disconnected callback
mqttClient.onDisconnected = _onDisconnected;
///Subscription success callback
mqttClient.onSubscribed = _onSubscribed;
///Subscription failure callback
mqttClient.onSubscribeFail = _onSubscribeFail;
}
static Mqtt getInstance() {
if (_instance == null) {
_instance = Mqtt._();
}
return _instance!;
}
///connection
connect() {
mqttClient.connect();
_log("connecting");
}
...
}
And I call like this
Mqtt mqtt = Mqtt.getInstance();
mqtt.subTopic = 'NOTIFICATION/';
mqtt.connect();
But mqtt disconnects when app is stopped.
How to call mqtt client in background service flutter?
Check flutter foreground service it might help you.
Related
I'm trying to receive data from a gadget with OSC Protocol, and with a port that I defined, I can receive the message in the Protokol android app. I want to receive messages in my app. I think the OSCpackage for flutter is not properly working, or maybe I made a wrong!
This is receive function:
int defaultPort = 12345;
void receiveOsc(List<String> args) {
final port = defaultPort;
final socket = OSCSocket(serverPort: port);
print(socket);
socket.listen((msg) {
print("${msg.toString()}");
socket.reply(OSCMessage('/received', arguments: []));
});
}
i Want to get messages in string format in my defined port.
We have a non clustered vertx application, and we use the event bus to internally communicate between verticles.
Verticle A consumes from the bus, performs a HTTP request, and sends the response back through the bus.
Verticle B just request to perform that HTTP request.
The problem appears when a "high" request volume is performed by Verticle B. Then, the consumer starts receiving the events slower and slower (presumably because they are getting queued in the event bus). For 8 requests/second the bus takes up to 3-4 seconds to consume the event. When the requests/second are elevated, it can take more than 30 seconds to consume it, so the bus timeout is triggered.
The thing is, Verticle A is really fast performing the HTTP operation (~200ms) so I don't really understand why the requests get stuck in the bus.
We've tried many solutions but none ot then worked:
Deploy multiple instances of Verticle A as workers
Use vertx.executeBlocking() to perform the HTTP request
The only thing that worked was commenting the HTTP request and returning a mock object through the bus. But again, the HTTP request doesn't take more than 200ms, so it shouldn't be blocking the bus.
Additional information: We use an autogenerated rest client that uses Retrofit + OkHttpClient. Due to company policy, we cannot use Vertx WebClient, so I didn't try this solution.
EXAMPLE
This is a really simplified version of our code so you can check if I'm missing something.
VERTICLE A
// Instantiated in Verticle A
public class EmailSender {
private final Vertx vertx;
private final EmailApiClient emailApiClient;
public EmailSender(Vertx vertx) {
this.vertx = vertx;
emailApiClient = ClientFactory.createEmailApiClient();
}
public void start() {
vertx.eventBus().consumer("sendEmail", this::sendEmail);
}
public void sendEmail(Message<EmailRequest> message) {
EmailRequest emailRequest = message.body();
emailApiClient.sendEmail(emailRequest).subscribe(
response -> {
if (response.code() == 200) {
EmailResponse emailResponse = response.body();
message.reply(emailResponse);
} else {
message.fail(500, "Error sending email");
}
});
}
}
VERTICLE B
// Instantiated in Verticle B
public class EmailCommunications {
private final Vertx vertx;
public EmailCommunications(Vertx vertx) {
this.vertx = vertx;
}
public Single<EmailResponse> sendEmail(EmailRequest emailRequest) {
SingleSubject<EmailResponse> emailSent = SingleSubject.create();
vertx.eventBus().request(
"sendEmail",
emailRequest,
busResult -> {
if (busResult.succeded()) {
emailSent.onSuccess(busResult.result().body())
} else {
emailSent.onError(busResult.cause())
}
}
);
return emailSent;
}
}
We fixed the issue changing our OkHttpClient configuration so HTTP requests won't get stuck
default void configureOkHttpClient(OkHttpClient.Builder okHttpClientBuilder) {
ConnectionPool connectionPool = new ConnectionPool(40, 5, TimeUnit.MINUTES);
Dispatcher dispatcher = new Dispatcher();
dispatcher.setMaxRequestsPerHost(200);
dispatcher.setMaxRequests(200);
okHttpClientBuilder
.readTimeout(60, TimeUnit.SECONDS)
.retryOnConnectionFailure(true)
.connectionPool(connectionPool)
.dispatcher(dispatcher);
}
I tried some examples of ZMQ on C++,C# and Python. I am trying to have Request-Reply pattern to connect Android device to PC running UWP with Xamarin forms.
Below is the Requestor code:
public void HelloWorld()
{
var timer = new Timer(60000);
timer.Start();
timer.Elapsed += (sender, args) =>
{
this.Cancel = true;
timer.Stop();
};
// Create
const string endpoint = "tcp://PC_ip:3245";
using (var request = new RequestSocket())
{
request.Bind(endpoint);
Thread.Sleep(2000);
while (!Cancel)
{
request.SendFrame("Requester says hello");
var reply = request.ReceiveFrameString();
Debug.WriteLine("Gets reply {0}",reply);
}
}
}
Reply socket code:
public void HelloWorld()
{
var timer = new Timer(60000);
const string endpoint = "tcp://PC_ip:3245";
timer.Start();
timer.Elapsed += (sender, args) =>
{
timer.Stop();
Cancel = true;
};
using (var replierSocket = new ResponseSocket())
{
replierSocket.Connect(endpoint);
Thread.Sleep(2000);
while (!Cancel)
{
var replyFromRequester = replierSocket.ReceiveFrameString();
Debug.WriteLine("Got reply {0}", replyFromRequester);
replierSocket.SendFrame("Response socket say hello");
}
}
}
Cancel is boolean
I went through some questions posted on this and added delay and these connection code blocks only trigger after button clicks on app.
While debugging , request.ReceiveFrameString() replierSocket.ReceiveFrameString(); are not even hit.
I am new to network programming , I understand that for REQ/REP pattern the code has to be in particular order which I traced and fixed I believe and turned off firewall on my PC so that firewall wont block my incoming connections from Android device.
PC_ip stands for IPv4 address I got from ipconfig /all for my wifi. I also tried external ip of my machine from sites like whatsmyip.org at ResponseSocket but I still dont get response between devices.
Please let me know what am I doing wrong.
Issue replication repository : GitHub/me/XamZeroMq
I'm working on a UWP application which should communicate via TCP/UDP to a remote device. My issue is that the UWP app successfully sends UDP messages to the remote device, but does not receive the replies.
Here follows the code extracted from the app (simplified):
async Task TestUdpIP()
{
// Writer to the DatagramSocket
DataWriter writer;
using (var udpClient = new DatagramSocket())
{
try
{
// UDP Socket binding
udpClient.MessageReceived += UdpClient_MessageReceived;
var controllerName = new Windows.Networking.HostName(controllerIpAddress.ToString());
await udpClient.BindEndpointAsync(controllerName, controllerIpPort.ToString());
var remoteHostName = new Windows.Networking.HostName(hostIpAddres.ToString());
await udpClient.ConnectAsync(remoteHostName, remoteHostPort.ToString());
// Create a message to send
string message = "Some message";
// Reset the counter of messages received back from the remote robot
messagesReceived = 0;
// Send the message
writer = new DataWriter(udpClient.OutputStream);
writer.WriteString(message);
await writer.StoreAsync();
// Wait for robot status messages
await Task.Delay(5000);
}
catch
{
}
}
}
void UdpClient_MessageReceived(DatagramSocket sender, DatagramSocketMessageReceivedEventArgs args)
{
// Just increment the number of messages received
messagesReceived++;
}
However the UdpClient_MessageReceived handler does not fire. I'm sure that UDP messages are correctly sent from the UWP app and that the remote device replies back as shown in the following screenshot from Wireshark (the test has been taken on the same PC where the UWP app is running)
.
(IP Address, Port) details are shown in the following list to better explain the picture above
UWP application: (192.168.1.108, 19000) to send and receive.
Remote device: (192.168.1.152, 15999) to receive and (192.168.1.152, 54697) to send
Note: this is a similar question, where the answer says that for whatever reason the DatagramSocket should fire some messages before being able to receive. In my example a message is sent out however the message received handler does not fire anyway.
Note: The UWP app has been granted the internet (client) and the internet (client and server) capabilities
Note: I've tried also this (more readable) approach to bind the inbound/outbound datagram socket on the UWP app obtaining the same results:
// UDP Socket binding
var controllerName = new HostName(controllerIpAddress.ToString());
var remoteHostName = new HostName(hostIpAddres.ToString());
EndpointPair endpointpar = new EndpointPair(controllerName,
controllerIpPort.ToString(),
remoteHostName,
remoteHostPort.ToString());
udpClient.MessageReceived += UdpClient_MessageReceived;
await udpClient.ConnectAsync(endpointpar);
Where is the issue? Many thanks!
Please try to also add the Private Networks (Client & Server) capability in your app's manifest.
On other hand, you can try the Official DatagramSocket sample to see whether the both devices can communicate with each other.
After some experimenting, I came out with the idea of using two different DatagramSocket instances: one to send out UDP messages, and one to listen for incoming messages. With this code, I've been able to send UDP messages to the remote device (as before) and also I've been able to receive UDP messages from the remote device.
async Task TestUdpIP_DifferentPorts()
{
// Writer to the DatagramSocket
DataWriter writer;
// Inbound and outbound DatagramSocket
DatagramSocket udpListener = new DatagramSocket();
DatagramSocket udpSender = new DatagramSocket();
try
{
// String containing the serializaed message
string serializedMessage = "Some message";
var controllerName = new HostName(controllerIpAddress.ToString());
var remoteHostName = new HostName(hostIpAddres.ToString());
// Bind listener
udpListener.MessageReceived += UdpClient_MessageReceived;
await udpListener.BindEndpointAsync(controllerName, controllerIpPort.ToString());
// Connect sender
await udpSender.ConnectAsync(remoteHostName, remoteHostPort.ToString());
// Reset the counter of messages received back from the remote robot
messagesReceived = 0;
// Send the message
writer = new DataWriter(udpSender.OutputStream);
writer.WriteString(JsonConvert.SerializeObject(message));
await writer.StoreAsync();
// Wait for robot status messages
await Task.Delay(1000);
}
catch (Exception ex)
{
// Some exception handling
}
udpSender.Dispose();
udpListener.Dispose();
}
void UdpClient_MessageReceived(DatagramSocket sender, DatagramSocketMessageReceivedEventArgs args)
{
// Just increment the number of messages received
messagesReceived++;
}
With this approach only the IP port (or service name) of the inbound listener needs to be specified. The framework will choose the next available outbound IP port.
Note: If I understand well the DatagramSocket.ConnectAsync(EndpointPair) documentation, the same DatagramSocket instance can be used to send and listen for incoming message, so I could not figure out the need for two different instances. From the documentation:
This ConnectAsync(EndPointPair) method on a DatagramSocket is used to define the local and remote endpoint where datagrams will be sent when using the OutputStream property. This method also restricts remote IP addresses of packets that will be accepted to the remote hostname in the endpointPair parameter. Only incoming packets that match the remote endpoint in the endpointPair parameter will trigger the MessageReceived event on the DatagramSocket.
I am newbie for WP7 and Socket programming. I have gone through msdn sample code http://msdn.microsoft.com/en-us/library/hh202864(v=VS.92).aspx#Y4537 and tested for use. Send works fine but it couldn't receive, this is the code I have used for receiving udp packet data.
In this my Breakpoint always fails # if (e.SocketError == SocketError.Success)
public string Receive(int portNumber)
{
string response = "Operation Timeout";
// We are receiving over an established socket connection
if (_socket != null)
{
// Create SocketAsyncEventArgs context object
SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();
socketEventArg.RemoteEndPoint = new IPEndPoint(IPAddress.Any, portNumber);
// Setup the buffer to receive the data
socketEventArg.SetBuffer(new Byte[MAX_BUFFER_SIZE], 0, MAX_BUFFER_SIZE);
// Inline event handler for the Completed event.
// Note: This even handler was implemented inline in order to make this method self-contained.
socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e)
{
try
{
if (e.SocketError == SocketError.Success)
{
// Retrieve the data from the buffer
response = Encoding.UTF8.GetString(e.Buffer, e.Offset,e.BytesTransferred);
response = response.Trim('\0');
}
else
{
response = e.SocketError.ToString();
}
_clientDone.Set();
}
catch (Exception ex)
{
ex.ToString();
}
});
// Sets the state of the event to nonsignaled, causing threads to block
_clientDone.Reset();
// Make an asynchronous Receive request over the socket
_socket.ReceiveFromAsync(socketEventArg);
// Block the UI thread for a maximum of TIMEOUT_MILLISECONDS milliseconds.
// If no response comes back within this time then proceed
_clientDone.WaitOne(TIMEOUT_MILLISECONDS);
}
else
{
response = "Socket is not initialized";
}
return response;
}
Have you tried using the specific UDP support in WP7/Silverlight? Either using UdpSingleSourceMulticastClient or UdpAnySourceMulticastClient depending on your scenario and requirements. Here's an intro article on UDP in Silverlight # Working with Multicast