How can I know on the server side when a client connected or disconnected from server?
Does ZeroC Ice provides some callback functions for those events?
Minimal demo:
Server side
try(com.zeroc.Ice.Communicator communicator = com.zeroc.Ice.Util.initialize(args))
{
com.zeroc.Ice.ObjectAdapter adapter =
communicator.createObjectAdapterWithEndpoints("Hello", "default -h localhost -p 10000");
adapter.add(new HelloI(), com.zeroc.Ice.Util.stringToIdentity("hello"));
adapter.activate();
communicator.waitForShutdown();
}
Client side
try(com.zeroc.Ice.Communicator communicator = com.zeroc.Ice.Util.initialize(args))
{
HelloPrx hello = HelloPrx.checkedCast(communicator.stringToProxy("hello:default -h localhost -p 10000"));
hello.sayHello();
}
From the Server side you can check current.con member and register a close callback if it's a connection that hasn't been seen before see setCloseCallback
current is com.zeroc.Ice.Current parameter passed to all servant methods, for example in sayHello implementation you can do
#Override
public void sayHello(int delay, com.zeroc.Ice.Current current)
{
// Check if current.con is a new connection, you will
// need to keep track of that in your code.
// Install a close callback for the connection.
current.con.setCloseCallback(con ->
{
// Close callback
});
}
Related
I have this in my code:
useEffect(() => {
if(loaded2 == false){
connection = signalr.hubConnection('https://webambe.com/xxx');
connection.logging = true;
proxy = connection.createHubProxy('xxx');
//receives broadcast messages from a hub function, called "helloApp"
proxy.on('updateAll', (argOne) => {
setAlertNum(1);
//Here I could respond by calling something else on the server...
});
// atempt connection, and handle errors
connection.start().done(() => {
//console.log("dddd" + proxy.connectionState);
setLoaded2(true);
//console.log('Now connected, connection ID=' + connection.id);
setTrans(false);
}).fail(() => {
//console.log('Failed');
});
//connection-handling
connection.connectionSlow(() => {
//console.log('We are currently experiencing difficulties with the connection.')
});
connection.error((error) => {
const errorMessage = error.message;
let detailedError = '';
if (error.source && error.source._response) {
detailedError = error.source._response;
}
if (detailedError === 'An SSL error has occurred and a secure connection to the server cannot be made.') {
//console.log('When using react-native-signalr on ios with http remember to enable http in App Transport Security https://github.com/olofd/react-native-signalr/issues/14')
}
//console.debug('SignalR error: ' + errorMessage, detailedError)
});
}
});
When the code hits connection.start().done((), then the connection should be established but when I hit the send button that invokes the hub i get this error (setLoaded2(true) means that the connection is established):
Connection has not been fully initialized. Use .start().done() to run the logic after
connection has started.
But I have stated that says that connection has started here:
setLoaded2(true);
When this is called setTrans(false) is called to get rid of the transparent view so users can interact with the UI.
The hub connects successfully and I can run commands to the server and back, but I just want to know how to say when the connection is established so that the user can use the system.
I'm not sure if this is the way it shud be done but its working and staying connected when I move the connection and proxy outside my functional component:
connection = signalr.hubConnection('https://webambe.com/xxx');
connection.logging = true;
proxy = connection.createHubProxy('xxx');
when added this code outside the component the connection stays connected and no issues with signalr
I have a ratchet server, that I try to access via Websocket. It is similar to the tutorial: logging when there is a new client or when it receives a message. The Ratchet server reports having successfully established a connection while the Kotlin client does not (the connection event in Kotlin is never fired). I am using the socket-io-java module v.2.0.1. The client shows a timeout after the specified timeout time, gets detached at the server and attaches again after a short while, just as it seems to think, the connection did not properly connect (because of a missing connection response?).
The successful connection confirmation gets reported to the client, if the client is a Websocket-Client in the JS-console of Chrome, but not to my Kotlin app. Even an Android emulator running on the same computer doesn´t get a response (So I think the problem is not wi-fi related).
The connection works fine with JS, completing the full handshake, but with an Android app it only reaches the server, but never the client again.
That´s my server code:
<?php
namespace agroSMS\Websockets;
use Ratchet\ConnectionInterface;
use Ratchet\MessageComponentInterface;
class SocketConnection implements MessageComponentInterface
{
protected \SplObjectStorage $clients;
public function __construct() {
$this->clients = new \SplObjectStorage;
}
function onOpen(ConnectionInterface $conn)
{
$this->clients->attach($conn);
error_log("New client attached");
}
function onClose(ConnectionInterface $conn)
{
$this->clients->detach($conn);
error_log("Client detached");
}
function onError(ConnectionInterface $conn, \Exception $e)
{
echo "An error has occurred: {$e->getMessage()}\n";
$conn->close();
}
function onMessage(ConnectionInterface $from, $msg)
{
error_log("Received message: $msg");
// TODO: Implement onMessage() method.
}
}
And the script that I run in the terminal:
<?php
use Ratchet\Server\IoServer;
use agroSMS\Websockets\SocketConnection;
use Ratchet\WebSocket\WsServer;
use Ratchet\Http\HttpServer;
require dirname(__DIR__) . '/vendor/autoload.php';
$server = IoServer::factory(
new HttpServer(
new WsServer(
new SocketConnection()
)
)
);
$server->run();
What I run in the browser for tests (returns "Connection established" in Chrome, but for some reason not in the Browser "Brave"):
var conn = new WebSocket('ws://<my-ip>:80');
conn.onopen = function(e) {
console.log("Connection established!");
};
conn.onmessage = function(e) {
console.log(e.data);
};
What my Kotlin-code looks like:
try {
val uri = URI.create("ws://<my-ip>:80")
val options = IO.Options.builder()
.setTimeout(60000)
.setTransports(arrayOf(WebSocket.NAME))
.build()
socket = IO.socket(uri, options)
socket.connect()
.on(Socket.EVENT_CONNECT) {
Log.d(TAG, "[INFO] Connection established")
socket.send(jsonObject)
}
.once(Socket.EVENT_CONNECT_ERROR) {
val itString = gson.toJson(it)
Log.d(TAG, itString)
}
}catch(e : Exception) {
Log.e(TAG, e.toString())
}
After a minute the Kotlin code logs a "timeout"-error, detaches from the server, and attaches again.
When I stop the script on the server, it then gives an error: "connection reset, websocket error" (which makes sense, but why doesn´t he get the connection in the first time?)
I also tried to "just" change the protocol to "wss" in the url, in case it might be the problem, even though my server doesn´t even work with SSL, but this just gave me another error:
[{"cause":{"bytesTransferred":0,"detailMessage":"Read timed out","stackTrace":[],"suppressedExceptions":[]},"detailMessage":"websocket error","stackTrace":[],"suppressedExceptions":[]}]
And the connection isn´t even established at the server. So this try has been more like a down-grade.
I went to the github page of socket.io-java-client to find a solution to my problem there and it turned out, the whole problem was, that I misunderstood a very important concept:
That socket.io uses Websockets doesn´t mean it is compatible with Websockets.
So speaking in clear words:
If you use socket.io at client side, you also need to use it at the server side and vice versa. Since socket.io sends a lot of meta data with its packets, a pure Websocket-server will accept their connection establishment, but his acknowledgement coming back will not be accepted by the socket.io client.
You have to go for either full socket.io or full pure Websockets.
I tried to search in api docs as well as examples, but there weren't any example demonstrating how to send pings and receive pings. The only example was of how to connect to websocket and to send a text here.
I also saw chat sample here of server side and i carefully followed that as well (i.e. set ping interval in server side configuration of WebSocket installation).
I start listening both side for pongs but none of the side was receiving any ping messages.
And there is no option to configure the client side for pings as you can see here.
I'm so much confused about how to send pings.
This is my server side:
embeddedServer(
CIO,
80
) {
install(io.ktor.websocket.WebSockets) {
pingPeriod = Duration.ofSeconds(20)
}
routing {
webSocket("/ws") {
for (frame in incoming) {
when (frame) {
is Frame.Pong -> {
println("ping's response recieved")
}
is Frame.Ping -> {
// just temporary block
println("ping recieved")
}
is Frame.Text -> {
println(frame.readText())
}
}
}
}
}
}.apply { start() }
This is my client side:
val client = HttpClient(CIO) {
install(WebSockets)
}
client.ws(
method = HttpMethod.Get,
host = "127.0.0.1",
port = 80,
path = "/ws"
) {
send(Frame.Text("Hello World!"))
for (frame in incoming) {
when (frame) {
is Frame.Pong -> {
println("ping's response received")
}
is Frame.Ping -> {
// just temporary block
println("ping recieved from server")
}
is Frame.Text -> {
println(frame.readText())
}
}
}
}
Result:
Hello World!
i.e websocket is connected, text are able to transferred, but unfortunately can't use ping/pong feature.
I also found some functions for this here pinger and ponger but now it says its part of api and gets automatically start with initiation of WebsocketSession and i also tried to put pinger in client side but that didn't send ping to server whatsoever.
Result of above code is simply Hello world gets printed in server console as sent from client side but no ping received messages.
I was having trouble getting OkHttp to use ping/pong so I filed this issue https://github.com/ktorio/ktor/issues/1803 and one of the developers replied "well the only thing I can recommend you is to try CIO out. Is does support manual Ping/Pong processing using RawWebSockets."
Haven't tried it myself but you should check out https://github.com/ktorio/ktor/blob/master/ktor-features/ktor-websockets/jvm/test/io/ktor/tests/websocket/RawWebSocketTest.kt
Here is my paho client code
// Create a client instance
client = new Paho.MQTT.Client('127.0.0.1', 1883, "clientId");
// set callback handlers
client.onConnectionLost = onConnectionLost;
client.onMessageArrived = onMessageArrived;
// connect the client
client.connect({onSuccess:onConnect});
// called when the client connects
function onConnect() {
// Once a connection has been made, make a subscription and send a message.
console.log("onConnect");
client.subscribe("/World");
message = new Paho.MQTT.Message("Hello");
message.destinationName = "/World";
client.send(message);
}
// called when the client loses its connection
function onConnectionLost(responseObject) {
if (responseObject.errorCode !== 0) {
console.log("onConnectionLost:"+responseObject.errorMessage);
}
}
// called when a message arrives
function onMessageArrived(message) {
console.log("onMessageArrived:"+message.payloadString);
}
On Rabbitmq server everything is default seetings. When i run this code i get WebSocket connection to 'ws://127.0.0.1:1883/mqtt' failed: Connection closed before receiving a handshake response
What i am missing ?
From my personal experience with Paho MQTT JavaScript library and RabbitMQ broker on windows, here is a list of things that you need to do to be able to use MQTT from JS from within a browser:
Install rabbitmq_web_mqtt plugin (you may find latest binary here, copy it to "c:\Program Files\RabbitMQ Server\rabbitmq_server-3.6.2\plugins\", and enable from command line using "rabbitmq-plugins enable rabbitmq_web_mqtt".
Of course, MQTT plugin also needs to be enabled on broker
For me, client was not working with version 3.6.1 of RabbitMQ, while it works fine with version 3.6.2 (Windows)
Port to be used for connections is 15675, NOT 1883!
Make sure to specify all 4 parameters when making instance of Paho.MQTT.Client. In case when you omit one, you get websocket connection error which may be quite misleading.
Finally, here is a code snippet which I tested and works perfectly (just makes connection):
client = new Paho.MQTT.Client("localhost", 15675, "/ws", "client-1");
//set callback handlers
client.onConnectionLost = onConnectionLost;
client.onMessageArrived = onMessageArrived;
//connect the client
client.connect({
onSuccess : onConnect
});
//called when the client connects
function onConnect() {
console.log("Connected");
}
//called when the client loses its connection
function onConnectionLost(responseObject) {
if (responseObject.errorCode !== 0) {
console.log("onConnectionLost:" + responseObject.errorMessage);
}
}
//called when a message arrives
function onMessageArrived(message) {
console.log("onMessageArrived:" + message.payloadString);
}
It's not clear in the question but I assume you are running the code above in a web browser.
This will be making a MQTT connection over Websockets (as shown in the error). This is different from a native MQTT over TCP connection.
The default pure MQTT port if 1883, Websocket support is likely to be on a different port.
You will need to configure RabbitMQ to accept MQTT over Websockets as well as pure MQTT, this pull request for RabbitMQ seams to talk about adding this capability. It mentions that this capability was only added in version 3.6.x and that the documentaion is still outstanding (as of 9th Feb 2016)
I have a locally hosted WCF service and a silverlight 5 app that communicates with it. By default silverlight tries to obtain the cross domain policy file over HTTP when making calls to the WCF service. I need to change this so that the policy file is served over net.tcp port 943 instead.
I have setup a local tcp listener that serves up the policy file over port 943 and i have followed this technique whereby i make a dummy socket connection in order to obtain the policy file over tcp as it is only retrieved once per application lifetime. The tcp server is being hit as expected and i am getting SocketError property value as Success (though i must note, the first time i hit the tcp server after starting the listener, the result is always access denied).
From what i can tell, the policy file is either invalid as the silverlight application as still unable to connect or the above mentioned technique does not work with silverlight 5.
What i would like to know is if what i am doing is possible & im doing it correctly, otherwise if there is an alternative means to have the policy file successfully downloaded over tcp and removing the need for retrieving it over HTTP.
Thanks
I wrote a long post about hosting silverlight in WPF - and using WCF with a http listener here:
How can I host a Silverlight 4 application in a WPF 4 application?
Now while not directly answering your question, it does show how to create a http version of the policy file.
I have also written something that serves up a policy listener over port 943, but I can't find where I posted the source - so I'll keep digging. As far as I remember though, silverlight does a cascade find of the policy file, if it doesn't get a connection on port 80, it'll then look on port 943.
I hope this is of some help somewhere.
Ok, here is the policy listener I had for net.TCP transport i.e. not HTTP based. I presume you have sorted this by now, sorry for the delay. It may well be of use to someone else now.
I was looking for the MS thing that said they cascade from HTTP to TCP, however, I can't, and therefore have to assume it was bunk and then changed.
Either way, if you call using a net.TCP service, and want a listener for it, this code should help:
#region "Policy Listener"
// This is a simple policy listener
// that provides the cross domain policy file for silverlight applications
// this provides them with a network access policy
public class SocketPolicyListener
{
private TcpListener listener = null;
private TcpClient Client = null;
byte[] Data;
private NetworkStream netStream = null;
private string listenaddress = "";
// This could be read from a file on the disk, but for now, this gives the silverlight application
// the ability to access any domain, and all the silverlight ports 4502-4534
string policyfile = "<?xml version='1.0' encoding='utf-8'?><access-policy><cross-domain-access><policy><allow-from><domain uri='*' /></allow-from><grant-to><socket-resource port='4502-4534' protocol='tcp' /></grant-to></policy></cross-domain-access></access-policy>";
// the request that we're expecting from the client
private string _policyRequestString = "<policy-file-request/>";
// Listen for our clients to connect
public void Listen(string ListenIPAddress)
{
listenaddress = ListenIPAddress;
if (listener == null)
{
listener = new TcpListener(IPAddress.Parse(ListenIPAddress), 943);
// Try and stop our clients from lingering, keeping the socket open:
LingerOption lo = new LingerOption(true, 1);
listener.Server.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Linger,lo);
}
listener.Start();
WaitForClientConnect();
}
private void WaitForClientConnect()
{
listener.BeginAcceptTcpClient(new AsyncCallback(OnClientConnected), listener);
}
public void StopPolicyListener()
{
if (Client.Connected)
{
// Should never reach this point, as clients
// are closed if they request the policy
// only clients that open the connection and
// do not submit a policy request will remain unclosed
Client.Close();
}
listener.Stop();
}
public void RestartPolicyListener()
{
listener.Start();
}
// When a client connects:
private void OnClientConnected(IAsyncResult ar)
{
if (ar.IsCompleted)
{
// Get the listener that handles the client request.
TcpListener listener = (TcpListener)ar.AsyncState;
// End the operation and display the received data on
// the console.
Client = listener.EndAcceptTcpClient(ar);
// Try and stop our clients from lingering, keeping the socket open:
LingerOption lo = new LingerOption(true, 1);
Client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Linger, lo);
// Set our receive callback
Data = new byte[1024];
netStream = Client.GetStream();
netStream.BeginRead(Data, 0, 1024, ReceiveMessage, null);
}
WaitForClientConnect();
}
// Read from clients.
public void ReceiveMessage(IAsyncResult ar)
{
int bufferLength;
try
{
bufferLength = Client.GetStream().EndRead(ar);
// Receive the message from client side.
string messageReceived = Encoding.ASCII.GetString(Data, 0, bufferLength);
if (messageReceived == _policyRequestString)
{
// Send our policy file, as it's been requested
SendMessage(policyfile);
// Have to close the connection or the
// silverlight client will wait around.
Client.Close();
}
else
{
// Continue reading from client.
Client.GetStream().BeginRead(Data, 0, Data.Length, ReceiveMessage, null);
}
}
catch (Exception ex)
{
throw new Exception(Client.Client.RemoteEndPoint.ToString() + " is disconnected.");
}
}
// Send the message.
public void SendMessage(string message)
{
try
{
byte[] bytesToSend = System.Text.Encoding.ASCII.GetBytes(message);
//Client.Client.Send(bytesToSend,SocketFlags.None);
Client.GetStream().Write(bytesToSend,0, bytesToSend.Length);
Client.GetStream().Flush();
}
catch (Exception ex)
{
throw ex;
}
}
}
#endregion