I have a client that sends a request to a server, and the server answer to him.
I want to do this in an asynchronous way. The client sends a request, the server calculates it and returns it to a service in the client. How can i do this?
p.s. let's say the client wants to do add(int a, int b) and the server needs to send the result to a service that run on the client.
A dual binding is only really needed when the server must send information to the client without a request. Since you are making a request, use one of the more basic bindings.
Making the request asynchronous is all about what the client does when it calls the service. One way of doing this is to get the generated client interface to include the event based asynchronous pattern.
When the client calls this method, it simply returns right away. An event is then triggered when the actual response to the request is received. The server itself is completely uninvolved with how the client waits for the response.
Related
I have grpc connection between client and server.
At the beginning client send message to server and connection is created.
Server has a background process that after checking something and conditions are true it should send message to client.
How can i do this ?
You can't do anything without the client making a request. I assume what's actually important is that the client doesn't need to know when to make a request, because the server is effectively event-based.
Create a server-streaming method, and call it from the client. The server can provide responses whenever it wants, and the client will then need to read those responses and handle them.
Is it possible to send message from one client to another client that is connected to the same server?
I want send data from one client to server Then send to specific client. I think I need to get client ID but I dont know how to get this id and how to send this message to that client from server.
I have a sample here. This is a chat server-client application. Multiple clients can connect to the server. When a client writes a message, the server simply broadcasts it for all clients who are receiving server stream RPC.
https://github.com/cactuaroid/GrpcWpfSample
See these server side implementation. When a client calls Subscribe(), it awaits m_chatService.Added event. When a client calls Write(), it raises the event and event args ChatLog is written on responseStream.
https://github.com/cactuaroid/GrpcWpfSample/blob/f6e8c4b2493c23cdcbaffeca29b5bb6705fbe95c/GrpcWpfSample.Server/Grpc/ChatServiceGrpcServer.cs
https://github.com/cactuaroid/GrpcWpfSample/blob/f6e8c4b2493c23cdcbaffeca29b5bb6705fbe95c/GrpcWpfSample.Server/Model/ChatService.cs
You can add your logic such as specifying channel name to subscribe/write, or define OpenChannel(string password) to be called by client at the first time so that server can bind the client IP address to the channel, whatever as you like.
There's no special gRPC feature that would allow you to do this (all RPC are between a server and a client, there's no "broadcast" or "selective broadcast" feature to reach out to other clients connected to the same server.
The logic you want is something that can definitely be implemented and but details of such solution depend on your need. A naive approach that might work is e.g. this:
each client opens a bidi-streaming call to the server
server keeps a directory of connected clients
once server receives a message from a client, it selects which client it should forward to based on the directory.
server forwards the message to a client.
Needless to say this setup feels a bit complicated (you're basically implementing your own network protocol on top of gRPC), so even though it might be just the right thing for you to do, it would make sense to think about how to simplify the protocol so that you can use features directly supported by gRPC.
I have a requirement to return streamed response from WCF service.
The client would call GET on WCF REST URI and the server would send XML response when available. If no response is available, server would send a dummy XML response every few seconds to keep the connection alive.
I know this should ideally be done using Signal R (WebSockets) but I would like to know if there is a way to achieve this in WCF (without using Signal R).
I don't have to return large data, I would like to send intermittent small sized XML data.
Let me know if someone has achieved something like this with WCF REST?
I am not sure how flexible you are by using WebAPI, sorry if its not what you want, but I came across this code below which is basically an api controller that pushes data back to the client on a continuous basis as HTTP response..
The client is basically a HttpClient which connects to a Uri address issuing a GET HttpRequestMessage. The message is sent with SendAsync and the stream is received as response.Content.ReadAsStreamAsync()...
Here is the link: http://aspnet.codeplex.com/SourceControl/changeset/view/bb167f0b0013#Samples/Net4/CS/WebApi/PushContentControllerSample/PushContentController/Controllers/PushContentController.cs
The best way to create a persistent connection between server and client is to use WebSockets.
WCF can use WebSockets via the NetHttpBinding.
Once configured, you can force communication to always be over WebSockets via:
transportUsage=Always
Since you have a persistent connection, you will need to use callbacks to manage application flow when data is sent across.
There's also a detailed article here describing a few different ways to create WebSocket connections in .NET (without SignalR).
Create a WCF Service that Communicates over WebSockets
I have a server which is connected to a few clients (with WCF and netTcpBinding).
At an undefinite point in time I want the server to call the method of a specific client (and have a string as a parameter). The server only knows which client when he wants to call it.
Basically one client has to wait for a server to send him a message (but in the meantime, other clients call the server as well) and the server needs to know exactly which client he needs to call. (The client has an attribute and the server wants to call the method on the client with a specific attribute)
Is there a way to do this?
EDIT: I thought of a possibility, but I think there is a better way.. for the moment the client will call a method with parameters specifying the ip and port of the client. The server will add it to a list and when the server wants to call the client, he searches the list for the attribute and connects to the client (on the client a service is hosted as long as the client is waiting)
WCF already has support for this built in. You need to create a duplex contract. The server can then call any connected clients whenever it wants.
I'm working on a protocol which is designed to be implemented with SOAP over HTTP.
WSDL files are provided by a third party.
I used wsdl.exe to generated a proxy class and created a Web Service Project in VS.
wsdl.exe yourFile.wsdl /l:CS
I got a cs from a unwrapping wsdl.
Snippet:
[System.Web.Services.Protocols.SoapHeaderAttribute("chargeBoxIdentity")]
[System.Web.Services.WebMethodAttribute()]
[System.Web.Services.Protocols.SoapDocumentMethodAttribute("/ClearCache", RequestElementName="clearCacheRequest", RequestNamespace="urn://Ocpp/Cp/2012/02/", ResponseElementName="clearCacheResponse", ResponseNamespace="urn://Ocpp/Cp/2012/02/", Use=System.Web.Services.Description.SoapBindingUse.Literal, ParameterStyle=System.Web.Services.Protocols.SoapParameterStyle.Wrapped)]
[return: System.Xml.Serialization.XmlElementAttribute("status")]
public abstract ClearCacheStatus ClearCache();
Implementation 1 (Server Side)
A central system (Server) connected to devices. When a device initialized, it sends an authorisation to central system.
And Server response an authorisation message back.
I have already done with Server Side which provides all clients send requests to Server. And Server response the messages.It works well.
Implementation 2 (Central system send a message to a device)
The other part of implementation is a central system need to send message to device (ex. clear devices cache, please see a snippet above). I add those methods to web service as well.
My questions are...
How can I send a message to devices through a proxy from Web Service?
It's impossible to call a method from Web Service sending requests to device? Any suggestions?
Or I need to create a project implementing a ClearCache method and format as a SOAP message to trigger?
Thanks!
I dont think it is a good idea to allow the Central system to directly communicate with the clients (Will create a huge noise in the network if the number of devices is high and the server tries to send several messages)..
A better approach will be to allow all the messages that the server intends to send to the client to be cached locally in the server machine. The clients should periodically communicate with the server using another web service and obtain the cached information that you intend to send to the clients.
you can design a method that sends the guid of the client as a parameter in the web service call.
On the server you maintain a database and keep track of the messages that needs to be sent to the clients.
use a timer object in the clients. On elapse of the timer define a method that communicates with the server by sending its guid. On the server side use this guid as a Primary Key to identify wat messages need to be sent to the client and then reply that while returning from the message.
The client then uses this return value to decide how to respond.