Question about C#, servers, XML

Question

So I'm working on a project for my internship and have hit a bit of a brick wall. Unfortunately, the only people I know who are qualified to help me at the office are on vacation at the moment, and Google has been unfortunately unhelpful (or my search skills inadequate), so I thought I'd ask here.

The project is basically to make a server to mimic one that the company (which makes phone apps) already has. What I need to do is have one of their apps send a request to my server (I will have to modify the app to do this, but don't know how), and have my server reply with an XML response that the app already knows how to process. (The main purpose is so that we can see how the app responds when the real server sends it an error by simulating it on my server.)

Now, I already have a few sample HTTP requests and their associated XML responses handy, taken from simulations with the app and the real server. The app is written in C#, and currently sends HTTP web requests to the real server's online location, which responds to these HTTP web requests with XML. My server, however, will not have an online location, so the app will have to be modified to work with sockets on a local host.

My questions:

1) My boss said to create an XML file to associate certain requests with certain XML responses, but I have no idea what he means or how to do this. (He said it could also be done with a .ini file.) Does anyone know?

2) Once I have this XML file that can make these associations, how can I incorporate it into my server so that my server can check the request it received against its table of valid requests and figure out which response to send back?

3) How can one modify the app from using HTTP web requests and responses to using sockets?

If you have any questions/clarifications that you need in order to better answer this, please don't hesitate to ask me.

Thanks!

Answer 1

What you're describing is a web service. Unfortunately, his advice to change a setting in an .ini file make it sound like they have a proprietary system for doing this, rather than using a standard ASMX (which requires IIS) or WCF (which can either run in IIS or as a standalone service, which it sounds like is what you'd want) service.

Without more information about what they're using, I don't know that you'll be able to get much help here.

Answer 2

Ask your boss if this client communicates with soap, if so then just go to MSDN and find tutorials on implementing an ASMX webservice, follow the tutorial through and you'll have a shell to start with.

Answer 3

In response to question #3:

HTTP is a protocol that already runs on a specific socket (normally using port 80). An internet socket is an endpoint that is used to transport data between processes. If you want to run your own protocol, you will need to create a new socket (with TCP or UDP) on a specific port.

This will however require you to create your own client and server in order to exchange data between them.

To get started, here is a very simple client-server example in C# using a custom socket.

Good luck!

Answer 4

First I'd like to say that it sounds like you have some unclear requirements that you should probably clarify with your boss. If you're not exactly sure what he means you should find out because nothing sucks more than having to support someone's creative interpretation of requirements.

1) It sounds like your boss just wants a way to easily change associations for testing without having to rebuild the app so he's asking you to store those associations in an xml/ini file that can easily be modified. In c# you can easily go between XML and DataSet objects so this should be trivial. I would create the data structure in a DataSet first and then use the GetXml method of the DataSet to output the xml format.

2) In .NET you can store objects in Cache and create a Cache Dependency that is a file association. Thus whenever the file is modified the Cache is purged. Whenever your program handles a request it pulls the object from Cache, if the object isn't in Cache then you have a condition block rebuild it from the xml/ini file on disk. I would have that condition block call out to a function that then loads the above mentioned xml format into a dataset that is then stored in the Cache with a Cache Dependency.

3) If you are trying to test an applications i/o, modifying it to use a different transport layer sounds like a bad idea. If the app currently works over HTTP to send requests then just route the HTTP request. I would suspect that the app probably has a configuration somewhere defining the path of the webservice it currently calls out to, once you know what that path is you can either change it, or if that's not possible setup a DNS rule on the server running the app to route it to the location of your application. On windows this is as simple as adding a line to the hosts file.