I have a desktop application which connects to a web server via WebSockets. While the connection is open the server can send the client application commands. When the client has executed the command he tells the server that he has completed the task. When this message arrives on the server the WebSocket middleware executes a ReceiveAsync method.
I need to await the response of the client on the server, since I need to do some additional stuff based on the initial command.
Here's and example on how a communication could be done. In this case we are going to tell the client to create a new file.
Client connects to the server via Websocket. The server stores the Websocket with a GUID.
The server sends a "CreateFile" command to the server.
The client receives the command and create a new file.
The client sends a "Created File with name abc.xyz" message back to the server.
The server the registers the file in its internal database to do additional work.
My current state is an asynchronous SendMessage method that I can await. However now I need a way to await the response part.
I already read about a possibility with the TaskCompletionSource and then Task.WhenAll(). I also read about the possibility with a ManualResetEvent.
Currently I'm a bit confused how I should approach this problem.
Related
From my understanding, the beauty of signal R is that it takes care of the "handshake" between the client and server to determine the best form of communciation between them (websockets, long polling, etc). I understand that by default it does this at the /signalr route. I read that before this the handshake would be accomplished with an HTTP Get request with an Upgrade/Connection header specifying to upgrade to this new connection.
In my current application we support handling many HTTP requests in a RESTful manner. If we wanted to expose some of this data in real time rather than in this request response format, what would be the best way to determine if we should open a connection using signal R? Would checking for those headers still suffice? I just feel like that is a bit redundant since signal R abstracts that away.
Instead of this, would a solution be for the client to specifically invoke a hub method to kick off the streaming as soon as he connects to the proper endpoint?
TLDR: Need a way to open a signal R connection from a HTTP request, don't know the best way to go about that whether it be from requesting the resource with custom HTTP headers or by just navigating to the url resource and having their client invoke a hub method.
A typical example of using signalr is:
an html file using JavaScript to connect to a signalr Server when the page is loaded. we call this signalr client.
a signalr server written in c#. it can be a winform or console or service.
the signalr Server can call any dll, or webservices or webapi located in the same server, or even in different Server.
then, the client can call any function defined in the signalr server. the server can call any function defined in the client for a particular client or for groups of clients.
also, client x can call client y functions as well.
I would also suggest you create this index.html inside a Cordova project, so that your client can use this app using any pc desktop browser, or any mobile phone browser, or run it as an Android or iPhone native app, by using One set of client codes.
if they navigate to some url resource instead of receiving a response with json in its body we want them to be constantly in real time using signal r receiving data
I don't think this is possible with SignalR. Reason is that all SignaR communication is done through single route (xxx.xxx.xxx.xxx/signalR) + all SignaR connections are established using handshake (By client sending negotiate request to this route. Well maybe not all - not sure if negotiation is happening in case you initialize SignalR connection object with specific transport).
I am using C# to connect to a web service. I am need to send a GET request to monitor some transactions, and the web service will be sending the transactions to me continuously without breaking the connection. The web service provider said I need to connect to them with a http library that supports SSE.
I have tried using HttpWebRequest and HttpClient to send request and receive response, but both of my attempt failed. I don't get response from the web service.
My question is:
The web service will send the transactions to me without breaking the connection, but how do I keep the connection up? Do I have to set up a socket for listen after I send the GET request?
Thank you,
kab
I have the issue resolved. So basically, I send a httpclient request, then I tie the response stream to an event handler, so whenever there is data on the stream, the event will be raised.
Thanks for all of your inputs.
kab
I have a tcp server that writes in winforms and a client in android. I connect devices to a wirless network then I disconnect server from this network. However client continue to listen server for a while then it closes its socket. How can I tell client to close socket when server is disconnected from network?
The reason it happens (if I understand the problem correctly) is that there is not inherent way to know that a connection has been closed, unless you try to send a package. So in your client, if you try to send an empty package over the connection, it will immediately report if the connection has been closed.
This is the reason that Heartbeats exist, and you can configure your socket to use them, or you can have your client periodically (or when needed) attempting to send an empty package and report the status of the connection.
There is an excellent article on CodeProject about this, see here.
For the case of an SignalR client using .Net Framework 4.0 to connect to the server (therefore no WebSockets transport supported) which would be the next fallback transport ?
Moreover, if there is a fallback chain it would be great to know it.
From https://learn.microsoft.com/en-us/aspnet/signalr/overview/getting-started/introduction-to-signalr#transports-and-fallbacks the following are used if WebSockets is unavailable:
Server Sent Events, also known as EventSource (if the browser supports Server Sent Events, which is basically all browsers except Internet Explorer.)
Forever Frame (for Internet Explorer only). Forever Frame creates a hidden IFrame which makes a request to an endpoint on the server that does not complete. The server then continually sends script to the client which is immediately executed, providing a one-way realtime connection from server to client. The connection from client to server uses a separate connection from the server to client connection, and like a standard HTML request, a new connection is created for each piece of data that needs to be sent.
Ajax long polling. Long polling does not create a persistent connection, but instead polls the server with a request that stays open until the server responds, at which point the connection closes, and a new connection is requested immediately. This may introduce some latency while the connection resets.
Update:
The latest docs are available here: http://www.asp.net/signalr/overview/signalr-20/getting-started-with-signalr-20/introduction-to-signalr
I'm trying to build a simple multithreaded tcp server. The client connects and sends data to server, the server responds and waits for data again. The problem is I need the server to listen for incoming data in separate thread and be able to send command to client any time (for example to notify about new update). As far as I understood, when ever client sends data to server, if server doesn't respond with any data, client app doesn't let me send more data, server simply doesn't receive them. If I send data ether way around, does the data need to be 'acknowledged' for tcpclient?
Here's the source for the server: http://csharp.net-informations.com/communications/files/print/csharp-multi-threaded-server-socket_print.htm
How can I make the server send command to a client in separate thread outside the "DoChat" functions loop? or do I have to handle everything in that thread? Do I have to respond to each request client sends me? Thanks!
The problem is I need the server to listen for incoming data in separate thread
No, there is an async API. You can polll a list of threads to see which ahve new data waiting, obcviously to be done froa worker thread.
As far as I understood, when ever client sends data to server, if server doesn't respond with any
data, client app doesn't let me send more data, server simply doesn't receive them.
That is a lot more crap programming than the way sockets work. Sockets are totally ok with streaming ata in sending and receiving direction att the same time.
How can I make the server send command to a client in separate thread outside the "DoChat"
functions
Wel, me diong your job costs money.
BUT: The example is retarded. As in- totally anti pattern. One thread per client? You will run into memroy problems and perforamnce problems once 1000+ clients connect. You get tons of context switches.
Second, the client is not async because it is not written so. Mayy I suggest giong to the documentation, reading up on sockts an trying to build that yourself? THEN come back with questions that show more than "i just try to copy paste".
With proper programming this is totally normal. I have a similar application in development, sending data lall the time to the client and getting commands from the client to modify the data stream. Works liek a charm.
If I send data ether way around, does the data need to be 'acknowledged' for tcpclient?
Yes and no. No, not for TCP - TCP does it'Äs wn handshake under the hoods. Yes, if your protocol decides it has to, which is a programmer level design decision. It may or may not be necesssary, depending on the content of the data. Sometimes the acknowledgement provides more information (timestamp server side, tracking numer) and is not pure ly there for "I got it".