All the examples I have seen till now point me to a client server where a client has just one functionality (ex: get the server date and time) and the server just serves this functionality. So when the Server gets a request from the client it knows what business object's function has to called to serve the request.
But, when building complex applications (ex: a school management system) there are a lot of business objects on the server, now, how does the client tell the server which business object's function to be called.
This whole question is with regard to QT
You can use customize Signals and Slots for your purpose.
From Client side
Just emit signals with passing parameter as a job id or job name
ex: emit signalA(jobId);
and at server side, connect the signal to required function
ex: connect(client, SIGNAL(signalA(int jobId)), this, SLOT(functionA(int jobId)));
I hope this will help you in identifying the job
Related
I'm working on multiplayer, I can at the moment send data to the client, however, my server can't seem to receive data from the client.
I have a feeling I'm missing something in my Async Networking event, but I'm unsure. Here is a sample of the server to client code and what I'm trying to do.
the listeners are just lists, I can't post any more links to images so I hope this is enough.
Connection Listener Code
Server Async
OnNetworkAsyncEvent
serverSendClientID
clientDataListener
serverDataListener
ClientHandler create
serverHandler create
Found out what was wrong, the serverHandler needed to have an else statement then run through the data listener scripts as it was only checking the servers own socket.
I have following scenario:
User request for certain resource on server, This request is long running task and very like 2~3 seconds to 10 seconds. We issue a JobTicket to user, As our user want to wait.
On receiving request we store that request in persistence storage and issue a token to user as JobTicket (GUID).
User make connection with Hub to get information about that GUID.
In Background:
We have WAS Hosted as well as Windows Service to perform some operation on that request.
On complete, WAS Hosted/Windows Service call our Web Application that job has been completed.
From there based on job Ticket we identify which user and on its connection we let user know its job has been completed.
Now we have farm of servers, we are using Windows Server On Prem ServiceBus 1.1 which is working fine, But challenge we have is that we are not able to intercept ServiceBus based backplane message broadcast and message is going to all the client. As we have farm, user intermediately may have drop connection and connected to other server based on load balancer so we need to have scale out using Service Bus as its kind of seamless to integrate and we are also using for our internal purpose in our application so we don't want to user any other mix in complex solution.
I have tried using IHubPipelineModule but still Scale out message broadcast not passing thru that, I tried to hookup SignalR code directly and debug thru it but its taking long. I don't want to mess-up something arbitrary in actual code. As I can see that in OnReceive I can see message are coming, but not able to follow further. I just need small mechanism that I can intercept broadcast message and make sure that it goes to client it intended and not all the client by wasting resources, and security concern as well.
Please help me on this issue, it's kind of stuck from last 4 days and not able to come to any solution and same time I want to go with establish pattern and don't want to fork any special build for this kind of small issues which I am sure one of you expert knows how I can do that seamlessly.
Thanks,
Shrenik
After lots of struggling and not finding straight forward way, I have found the way as below for someone else in future it might help.
Scenario:
1. Web Farm: Host External User facing Web Pages
2. Backend Process: Which is mix of WebApi, SharePoint, Windows Service etc.
User from Web Page submit some request and get a unique id as return back. Internally on receiving request, we queue that request to Service Bus using TopicClient for processing.
There are pool of Windows Service watching on Message on Service Bus using SubscriptionClient and process that message. On completion of process which can run from 5 seconds to 30 seconds and some cases even more. We need to inform client that its job done if its waiting on web page or waiting for completion notification.
In this story, We are using SignalR to push job completion notification to client.
Now my earlier problem is How I let know from windows service to web application that job is done so send notification to client who submitted request.
One way is we hosted another hub internally in web application, Windows service act as client and call web application hosted hub, and in that hub method it will call external facing hub method to propagate message to specific client who submitted request, for which we are using Single user Group.
And as we have register service bus as backplane it will propagate to other servers and then appropriate client will get notification. So this is ideal solution and should work in most cases.
In above approach we have one limitation that, how Windows Service connect to Web Client, as we donot have windows auth, but we have openid based auth with ADFS. Now in such case Web Application required special code in which provide separate userid or password for windows service to communicate or have windows authentication also allowed for that hub for service account of windows service.
I was trying and trying how to remove all this hopes between interserver communication and again management of extra security.
So I did below with simplicity, though it tooks me whole night to find our internal of SignalR. But it works:
Approach is to send message directly to ServiceBus Backplane, and as all Web Server already hooked-up with ServiceBus backplane then they will get message.
Unfortunately SignalR doesn't provide such mechanism to send message directly to Backplane. I think its on pub/sub model so they don't want somebody to hack in their system :). or its violation of their pattern, but its make sense, in my case because of different roles and security, I have simplify code as below:
Create a ServiceBusMessageBus instance in my code, Same way as Below: Though I have created separate instance and store till lifetime of Windows Service, so I don't create instance every time:
ServiceBusMessageBus serviceBusBackplane = new ServiceBusMessageBus(new DefaultDependencyResolver(), new ServiceBusScaleoutConfiguration(connectionString, appName));
Create a ClientHubInvocation Object: This is a message which actually get created in SignalR infrastructure when Backplane based message broadcast:
ClientHubInvocation hubData = new ClientHubInvocation
{
Args = new object[] { msg },
Hub = "JobStatusHub",
Method = "onJobStatus",
State = null,
};
Create a Message object which accept by ServiceBusMessageBus.Publish, Yes, so this is a method which actually get called on base class ScaleoutMessageBus.Publish. This class is actually responsible for sending message to topic and other subscribers on other server nodes. Why not use that directly. Now to create Message Object, You need following code:
Message backplaneMessage = new Message(
sourceId,
"hg-JobStatusHub." + name,
new ArraySegment(Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(hubData))));
In above second parameter is something interesting,
In case if you want to publish to all the client then syntax is "h-", in my case specific group user, so syntax is "hg-.. You can check the code here: https://github.com/SignalR/SignalR/blob/bc9412bcab0f5ef097c7dc919e3ea1b37fc8718c/src/Microsoft.AspNet.SignalR.Core/Infrastructure/PrefixHelper.cs
Publish your message to backplane directly as below:
await serviceBusBackplane.Publish(backplaneMessage);
I wish this PrefixHelper class have been public.
Remember: This is not recommended way and doent insulate from future upgrade for SignalR, as its internal they may change so any upgrade might come with small hazale to change this code. But in summary this works. Hope SignalR Team provide some mechanisam out of box to send message directly to backplane instead.
Thanks
Have started using SignalR. Would like to clear few queries regarding how SignalR have implemented broadcasting basically how server is able to initiate the Communication ?
1> In normal scenario whenever we request for a let say .aspx page, the server renders the page and returns the reponse back to the client and the things is done
But How SignalR is able to continously able to execute in Background/Async in case of Ticker demo available on the ASP.net site.
I googled little bit and found IRegisteredObject is one of the way where the the object which need to be excuted continously need to register with HostingEnvironment but for that the class have to implement the IRegisteredObject interface but in case of ticker demo none of the class implements the IRegisteredObject interface.
Am I mssing something over here or SignalR uses totally different technique ?
SignalR utilizes 4 transports through which it handles data from the server. Only one transport is used at a time but SignalR has 4 to ensure server/client communication on a wide variety of devices/browsers. Here's the transports and a short technical description:
Long Polling, to receive data it uses an ajax request whose response is not released until there is data available on the server, once the server returns data on the held onto response the client then creates another request and waits for the next batch of data. To send data it creates a second ajax request.
Forever Frame, uses iframes through which the server pushes down javascript text which is then executed in the iframe, the iframe then propagates the execution up to the parent page which then handles the data. To send data SignalR uses ajax requests.
Server Sent Events, uses the EventSource object. Supported in nearly everything but IE. The EventSource object opens up a one way pipe through which the server can pump data through, allowing the client to receive data in real time. To send data SignalR uses ajax requests.
Web Sockets, uses the built-in browser WebSocket object which opens up a single, bi-directional channel through which data can be received and sent.
That's the essence of each of SignalR's transports, you can see an hour presentation in which David Fowler and Damian Edwards create a Lite version of SignalR here. It essentially highlights how SignalR works under the covers.
I am currently working on TCP multithread server and clients written in C#. I was looking around on Google and tried more than 5 examples but seems none of them can serve all requirements. As I am not familiar with networking, so it would be appreciated if someone can point me to the right direction.
Here are the requirements I need:
multithread, I need a server which can handle multiple clients, though those clients do not need to communicate each other.
continous operations, after clients connected to the server, they need to keep sending messages to each other, until the server drops all the clients. The server needs to identify each client. The clients do not need to disconnect from server on themselves, normally.
disconnection notification, most of those examples found on Google do not have this feature, I need the server to know when the connected client disconnects, so the server can notifiy the user.
Actually the closest example I found is this:
http://www.codeproject.com/Articles/22918/How-To-Use-the-SocketAsyncEventArgs-Class
But the problem I am facing is that the messages are inside the class Token, I included all those classes in my Window Form Application, which is my main application. Those information like client ID, client status, or actions to clients, will be performed in the Form. I dont know how to bring those variables from Token class to my Form.
This is another example seems can suit my purpose:
http://www.codeproject.com/Articles/2866/Multi-threaded-NET-TCP-Server-Examples
But I am not sure how to change it since it blocked my Form from displaying.
Thanks for help.
Some months later... First, you have to keep in mind that the window form isn't async native, you have to implement invoke methods to use the tcp AsyncCallback. Elsewhere to handle clients, you have to create a new dictionary like :
Dictionary<string, System.Net.Sockets> clientList;
It could be int in case of database ids or simply you could use the native system handle :
this.anonymousSock.Client.Handle
And adding them like this :
clientList.Add("ID", this.anonymousSock);
Finaly :
public void Send(string data, string id)
{
Socket Client = this.clientList[id];
byte[] byteData = Encoding.ASCII.GetBytes(data);
Client.BeginSend(byteData, 0,
byteData.Length, 0,
new AsyncCallback(SendCallback), Client);
}
While receiving, you could in this case identify client by checking your sockets entries or by using tokens.
And then no cpu/memory burn with threads.
For manually testing an HTTP client in my application, I'd like to use a tool which starts an HTTP server my application can connect to and that lets me respond to request from my application manually. I'm basically looking for a tool with a GUI that lists all incoming requests and allows me to select a status code and type a response message. I've already tested the functionality with unit tests but I also want to verify it manually with no mocking etc.
Sounds simple but I didn't find such a tool. I've found some that can be scripted but no interactive one. Do you know one?
This can probably be written relatively easily by creating the Swing GUI dialog popup inside the servlet servicing methods. Have never seen Tomcat running this way but probably it would. Only, mind the server time out. It may be not long enough for you to make an input and require to be configured, also on the client side. Also, parallel calls will make multiple popups that may be difficult to respond but probably this is a single client app.
As a simplest solution, server GUI can be simply disposed after call and newly created as the next call arrives. This will make eveything indepenent on how servlet container is managing the servlets (does it stays, is it destroyed, maybe class is unloaded, who knows). Advanced solution could include the "server servlet" that would interact through its own JSP page but then it may be complex to update it when the new call arrives (unless maybe refresh periodically).