After looking into WCF, I don't believe it can do what I need it to. What would be the appropriate way (if I have a server and client application, both C# .NET Console apps) to basically instruct the client to execute functions?
For example, if the client application has functions such as DownloadFTPFile(), CreateWindowsService(), IsServiceRunning(), etc. what would be the standard approach to telling them to execute this from the client?
I was initially just going to have the client interpret messages sent from the server, such as "downloadfile ftp://filename.zip" but I am wondering if there is a better way.
Client has Agent.
Agent connects to server, polls for cmomands
Agend executes comands.
THe server sending is tricky unless you control the environment. NAT for example makes "client sends" a nightmare. You also then open up the client for additional attacks with client polling the clietn firewall does not have tp open external access to the agent.
It is possible.
Use the callback functions along with duplexes in the WCF. You will be limited to the intranet usage or azure though, since only NetTcpBinding and NetTcpRelayBinding support it (WsHttpBinding is deprecated).
With WCF, any client can self-host a WCF service. This can make the client be a service. Add a little extra protocol between the client and the service, and you've got your wish.
Related
I want to control application (in my case it is corelDraw) ,I know I should use it's application object and I do this, but the issue now is I want to do this in webservice,
so as far as I understand if I put this code which control the application in the web-service ,my code will try to control the corel application which is on the server not on the client :(
so any hint/advice how could I do this, and control the application on the client not server ?!!!
As you already noticed web service runs on server and only result is passed to client.
Well you have a few options to control client machine over web service... Here is one of possible scenarios.
1. create web service that will provide commands for client
2. create windows service (client) that will consume your web service commands
3. inside windows service then just execute those commands in appropriate manner
Well I have to say this is not the prefered way I would take to automate corelDraw, but if you insist on using webservice as command provider it will do the job.
You need to ask yourself what is the difference between client and a server. Can a client be a server? Can a server be a client?
You make your client with CorelDraw installed to accept web-service request, i.e. effectively make it a web-service server, and then carry on as normal.
Although I would say web-service is not the best way to control such complex application as CorelDraw. I'd look in some other ways of communication between peers, like lower level network communication that would not have overhead of HTTP.
We want to implement a client server application. here is the scenario.
Server listens for client 24/7.
Server accept request for client and save it in DB for further process.
Once processing is done (it may take few hours), Server will response back to client.
in short , client and server listens for each other 24/7.
I want to implement it in C# but i also want that it should be accessibly from all platforms.
Also is it possible in WCF?
I agree with Yuck, this is a basic WCF scenario. There a few articles, videos and tutorials to get you started here http://msdn.microsoft.com/en-us/netframework/dd939784
I am looking to write an application that will take client data from a database, transfer it to our server application, manipulate that data and then pass it back to the client. I would like this to be as seamless as possible and as secure as possible. Also, the manipulation part of this could take several hours. The format of the data will be different for each client. To make the application as easy to maintain as possible, the simplest solution too.
What methods would people recommend for achieving this?
WCF will make your implementation easy. It looks like you are wanting to have the client -> server -> client communication asynchronous, since the server process can take hours, you don't want to block your client that long.
You probably want to define a server WCF service contract to allow the clients to load data to the server. You also want a client side WCF service contract that the server can use to send the results back when the processing is completed. OR you can have the server send a small message to the client WCF service telling it that "results are ready, come and get them when you are ready". You will need to coordinate this with some type of ID; the server tells the client to use this id when it wants to collect the results.
Have a look for duplex, asynchronous and peer-to-peer communication topics in WCF. There should be plenty of examples if you google around.
Please take a look at WCF framework of .NET 4.0.
1/backup the database in prod
2/download it,
3/restore in local
4/modify,
5/backup in local
6/upload
7/restore in prod
to download in https or sftp, with ip restriction
you can compress the database before download it too
I posted about this before to a degree, but after a few days of reading I have a better understanding of WCF and would like to get a bit of feedback before I start working on it.
I basically need to develop a server/client system. The "server" application (c# net console app) will be ran on a machine with a MySQL database, all software installation packages, and whatever else we need local to it. The "client" application (c# net console app) will be ran on the rest of our machines, and will maintain a direct connection to the server software. Using a web front-end, our administrators will be able to install software packages to the clients, create new services, etc.
Since we own all of the machines, and have to configure them anyways, Server Push is not a problem. We don't have to worry about firewalls or any sort of NAT settings as we can just go in and open the ports required for it to operate.
What initially confused me about WCF is I assocated a "WCF Service" with a server. However, since the majority of operations are actually going to be run on the "WCF Service", this is my logic.
1) Make the "client" application actually a "WCF Service" so that the exposed functions are actually ran on the proper machines.
2) Have the "server" application actually a "WCF Client", and issue all of the instructions/commands from here, and just use the return value to update the database/etc.
Would this be the proper method to go follow or should I look into WCF Duplex (Looked extremely confusing at first glance) or just start with raw sockets?
from what I gatther you're trying to do, you're correct. That is the client machines should really have a TCP/IP "server" running on them, and the centeral server machine would have the Tcp/IP "Client".
That way the TCP/IP client (The app running on your server machine) can initiate calls to each of the client machines.
Keep in mind also that a single application can be both a tcp/ip client and server. So your app that's running on the server machine could in turn also be a tcp/ip server that your admin uses to do stuff using a browser. Which effectively means that service is an HTTP service.
So, it is not a client/server thing. It is a hub-and-spoke arrangement of distributed computing. I think, WCF can very well be used. You have multiple servers and a coordinator (the client to all of these servers) that gets the work done from various servers and update the database.
So WCF is well-suited for you. The benefit of WCF is the easy configurability and handling the communication part. You don't have to take much pain for the management of sockets.
I am planning a SaaS system, to be written in C#, ASP.NET using WCF that has two separate components:
On a static IP web server in the cloud will be a web app, common to all clients.
Inside each client's office will be another app, installed on a server with IIS.
The site app will obviously be able to connect to the web services published on the web site. But here's the rub - I also want the web app to be able to initiate a connection to the site app... and the on-site server may not necessarily have a static IP. I can't control this, because we may have hundreds of clients at some point in the future, and we cannot limit our saleability by insisting that the customer has a server with fixed IP.
So, how to do this?
I could have the site apps "checking in" with the web every minute or so, to give the web app the possibility of responding with a "while you're here, please do x,y,z..." but that seems very inelegant. Also, if we're talking about hundreds of clients, I don't want to be bombarding my web server with all these "hi there!" messages if they're not actually required.
Is there a better way?
WCF? Here we go:
Use a message based approach (exchange message, no stateful method calls).
Clients connect to the server. Establish a HTTP-based TWO WAY CONNECTION. This way the server can call back to connected clients. This is standard WCF stuff and works well through NAT with version 4 of the .NET framework.
Voila. In case of a disconnect the client can re-connect, re-identify himself and gets the pending messages.
IIRC "push communication" is done by letting the client do a HTTP Request with an indefinate timeout. Then the server responds when he has something to say. After the respons the client immediately makes a new request.
It works out the same way like the server is making the connection and takes far less resources than polling.
Dynamic DNS is one possibility, but depends on your clients/customers.
If the site app is created by you, it only has to contact the web server when its address has changed (or when the site server/web app is restarted). Still, a keep-alive heart beat of, say, every 30 min. to 1 hour isn't a bad idea.
Edit: I think SNMP services may provide the answer but I'm not a networking expert. You'll have to do some digging or ask a separate question on stackoverflow.
What would you say about Comet technology?
Sounds like you'll definitely need some sort of registry on the server, then it could attempt to call out to the client apps if it needs work doing.
Generally it is client apps that check in with the server every X seconds - this is how Selenium grid works anyway. With a central hub with which clients register. When the hub receives a request to run some tests it passes the jobs out to the clients to perform.
You may not need the "checking in". The server could just attempt to call out to a registered client app until it finds one that is available.This way only the server would need a static address (could use a DNS name instead of an IP to make it more robust).
Also have a look at XMPP PubSub. This could be a more robust and standardised way to handle this.
In the end I decided to go with NetTcpBinding, for reasons best given by #Allon Guralnek here. It's worth clicking through and reading what he has to say...