I have a websocket that is created using this statement :
ws = new WebSocket(targetURL);
and my javascript runs all the function inside ws.onopen (which is only an alert, stating that the ws is opened).
However, after 15 minutes or so, I want to create a new connection of websocket using the same variable ws. I tried this again :
ws = new WebSocket(targetURL);
But this time, it does not look like that the ws.onopen function is not run (there is no alert stating that the ws is opened). So I assume that that statement cannot be used to create a new connection, can it?
Is there a way of doing it?
Thank you
Since you are creating a new object you must at attach an event handler. Handlers are associated with objects, not variables. Write your logic in a separated function, and assign that function to "ws.onopen" after creation.
Related
I'm new to node and to feathersjs, and for my first app, I'm trying to have different parts of it communicate using channels. I understand the operations and how they're used, but I don't understand how to establish a connection to a channel in the first place.
For example, here's some code from the official documentation:
app.on('login', (payload, { connection }) => {
if(connection && connection.user.isAdmin) {
// Join the admins channel
app.channel('admins').join(connection);
// Calling a second time will do nothing
app.channel('admins').join(connection);
}
});
Where does "connection" come from? There is no built-in function (unless I'm missing something obvious) in feathersjs to do this.
Thanks!
Channel is used in feathers to achieve real time.
In the server you need to configure socketio. Then it also requires the client to be connected to the server via socketio.
Where does "connection" come from?
connection is a js object that represents the connection the user has established by logging in.
Try doing a console.log(connection) to see what it contains.
connection is in this case passed by the Feathers framework in the function call to the function that you have quoted.
Once you have obtained this connection object then you can use it for adding the user to a channel, and many other things.
Is it possible to broadcast or emit data over to browser and catch it with javascript to treat it accordingly, using ReactPHP without Ratchet?
I have a periodicTimer on event-loop and sometimes it needs to broadcast or emit to users connected by a socket. I saw there was a class socket and in the examples on the React github project page it was instantiated but not used in web-flow, only on netcat. Is it possible to make it work natively on browsers like socket.IO or Ratchet?
The factory and connection works fine, I just don't know how to bind socket to send/receive data to the server with event-loop.
Broadcasting this is not super-special function.
First of all, you need save all user connection in global scope.
For example you have a class TestServer, it can contains attribute connections (type array). In method run you write loop.
For example this your connection event
$server->on('connection', function(ConnectionInterface $conn) {
$this->connections[] = $conn;
});
And write method
public function broadcast($message) {
foreach($this->connections as $conn) {
$conn->write($message);
}
}
Attention!
You must write code to delete disconnecting if user disconnect, and if you need, you can write logic about topics.
Does the Azure Service Bus Subscription client support the ability to use OnMessage Action when the subscription requires a session?
I have a subscription, called "TestSubscription". It requires a sessionId and contains multipart data that is tied together by a SessionId.
if (!namespaceManager.SubscriptionExists("TestTopic", "Export"))
{
var testRule = new RuleDescription
{
Filter = new SqlFilter(#"(Action='Export')"),
Name = "Export"
};
var subDesc = new SubscriptionDescription("DataCollectionTopic", "Export")
{
RequiresSession = true
};
namespaceManager.CreateSubscription(sub`enter code here`Desc, testRule);
}
In a seperate project, I have a Service Bus Monitor and WorkerRole, and in the Worker Role, I have a SubscriptionClient, called "testSubscriptionClient":
testSubscriptionClient = SubscriptionClient.CreateFromConnectionString(connectionString, _topicName, CloudConfigurationManager.GetSetting("testSubscription"), ReceiveMode.PeekLock);
I would then like to have OnMessage triggered when new items are placed in the service bus queue:
testSubscriptionClient.OnMessage(PersistData);
However I get the following message when I run the code:
InvalidOperationException: It is not possible for an entity that requires sessions to create a non-sessionful message receiver
I am using Azure SDK v2.8.
Is what I am looking to do possible? Are there specific settings that I need to make in my service bus monitor, subscription client, or elsewhere that would let me retrieve messages from the subscription in this manner. As a side note, this approach works perfectly in other cases that I have in which I am not using sessioned data.
Can you try this code:
var messageSession=testSubscriptionClient.AcceptMessageSession();
messageSession.OnMessage(PersistData);
beside of this:
testSubscriptionClient.OnMessage(PersistData);
Edit:
Also, you can register your handler to handle sessions (RegisterSessionHandler). It will fire your handle every new action.
I think this is more suitable for your problem.
He shows both way, in this article. It's for queue, but I think you can apply this to topic also.
I want to create an application where on page3 users start communicating via a sockjs websocket (they go through page1 and page2 to reach page 3). The code is working fine but I dont know why!
// Global scope
var sock;
// Inside a function page3, this is invoked when Page3 loads for the first time
function page3(){
// Local scope
sock= new SockJS("localhost:8080/messages);
sock.onopen= function(){
....
};
sock.onmessage= function(data){
....
};
}
My question is - when a message is sent from the server how is sock.onmessage accessed by program execution even though it is 'seen' only when Page3 is loaded the first time which is when function page3() is called?
Looks like sock is not imported (the error message is saying that it is whats undefined)
Perhaps if you could share more of the code we could see why
Found my own answer.
The question is actually related to visibility of event listeners on the client. And the answer to that is - all event listeners on the client, once activated (flow of program execution having "seen" them) remain active until they are removed.
So in the above case, even though function page3() was "seen" by program execution only once - when Page3 was loaded for the first time, sock.onmessage becomes activated as a (client) event listener during that page3() function call and continues to remain active until the socket is closed.
As such, there is no need for an explicit page3() function call to trigger sock.onmessage. It (sock.onmessage) will keep listening to socket events sent by the server.
I have a controller action that does the following things:
Gets a domain object from the database
Uses info on that object to find a data file (on disk) and writes contents of that file to the response output stream.
My problem is that the database connection is reserved for the duration of the action, including the (long) time required to stream the data. This results in a lot of unnecessary database connections when there are several users streaming data at the same time.
def stream() {
StreamDetails sd = StreamDetails.get(params.id)
// Extract info needed to read the stream
String filename = sd.filename
// The database connection is no longer needed, how to properly release it?
// Start writing the data stream to response output
// This may take a long time and does not use a db connection
streamService.writeToOutput(filename,response.getOutputStream())
}
I have tried:
Injecting the sessionFactory bean to the controller and calling sessionFactory.currentSession.close() before calling the service. However this causes a SessionException on the line calling the service, ie. before entering the writeToOutput() method (and nothing in that method needs a database connection). AND I don't think the session should be really closed, just released to the pool.
Copy-pasting the code from streamService.writeToOutput(...) to the controller to avoid the service call. In this case all the code gets executed but a SessionException is still thrown after the action is complete.
How to properly release the connection early?
Have you tried to inject the dataSource? You could use the DataSourceUtils to create a new connection that you can then use to get the filename. You can then manually close() this connection.
I don't know if you can use this connection in combination with gorm, so you might have to create a custom sql query as well.