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How to simulate "No Internet Connection" in Unit/Integration test in C#

I have a component that (by part) uses an internet connection. I wrote some UnitTests to ensure that to component is working. However, I would like to test the behaviour of the component without internet connections.
So, my goal is to somehow temporary disable internet, or the whole internet connection, and reactivate after test.

I would disable\enable like here local are connection in test initialization
[ClassInitialize]
SelectQuery wmiQuery = new SelectQuery("SELECT * FROM Win32_NetworkAdapter WHERE NetConnectionId != NULL");
ManagementObjectSearcher searchProcedure = new ManagementObjectSearcher(wmiQuery);
foreach (ManagementObject item in searchProcedure.Get())
{
if (((string)item["NetConnectionId"]) == "Local Network Connection")
{
item.InvokeMethod("Disable", null);
}
}
[ClassCleanup()]
// Enable local area connetcion

There are many ways in which the system could have "No Internet" and the answer really depends on what you mean.
As the accepted other answer suggests, you could simply disable the network interface. That guarantees you have no internet, but the computer also will know it has no network either.
A couple other options are
To remove your Default Gateway (this may require setting static IP settings in the control panel, though I'm sure you could do it programmatically as well)
This way, the computer still thinks it's connected, but it won't have any network access except on the local subnet
Remove DNS server settings, see above link.
This way, the computer has direct IP based access but to a regular user it would appear as if there was "no internet."

Whilst not a direct answer to your question I believe you may find some use in this tool - https://jagt.github.io/clumsy/download
I've used it at work to simulate different network conditions for an mobile app that I'm currently working on. It is possible to completely disable the network connection by setting packet drop to 100%.

Secure My ASP .NET Code For Presentation?

I have a web application , for presentation to my client they ask me to install it on their local server so they can test it , here is my question !?
Is there any way so i can publish uniquely for that server , i did put some limitation but many features in my app are open , so they can make a disk image from server and use it anywhere else ,
Is there any method to use so my web application check if this server is same server ( by hardware id or anything i don't have any idea ) then start to work !
I saw many codes but they are win forms for generating unique hid , but how can i connect done it with asp .net
EDIT
Could u take a look at this also ,
i am using system.management class
is this reliable i mean are they unique ?
private string GetUniqueID()
{
string cpuInfo = string.Empty;
ManagementClass mc = new ManagementClass("win32_processor");
ManagementObjectCollection moc = mc.GetInstances();
foreach (ManagementObject mo in moc)
{
if (cpuInfo == "")
{
//Get only the first CPU's ID
cpuInfo = mo.Properties["processorID"].Value.ToString();
break;
}
}
ManagementObject dsk = new ManagementObject(#"win32_logicaldisk.deviceid=""" + "C" + #":""");
dsk.Get();
string volumeSerial = dsk["VolumeSerialNumber"].ToString();
string HardWareUniqueID = volumeSerial + cpuInfo;
return HardWareUniqueID;
}
Appreciate your answers,
Thanks in advance

If you want to avoid having it "phone home" an alternative is to generate some kind of certificate and place it on the machine. Use a private key that only you know to encrypt the machine name and/or IP. Then have your app use your public key to decrypt it to verify that it is allowed to run on this server. Nobody who doesn't know your private key will be able to create valid certificates.

You hae a few choices...
Lock your web site to the single IP address you install it on. To make your life easier, check for that IP in a common page base class. (Note, you could also write HTTP handlers, but the base-class approach is easier.)
Put a 'phone home' call in the app that checks with your server every time it's started up. That way you can check if they have moved it or if multiple instances are running.
Use the built-in licensing features of .NET (the same one third-party developers use for controls, etc.)
The easiest... just put in a time-bomb that lets them test it for a few weeks, then automatically blocks access. Be smart though... persist the last-checked time so you can tell if they've rolled back their clock trying to get more usage.
Just make sure to distribute a web application, not a web project so you can distribute your code as a compiled bumary rather than having to ship the code-behind files. That will keep prying eyes out, but does make deployment more a pain since you always have to recompile with every change (as opposed to on-demand compiling.)

I would put in a time bomb. It's trivial to implement. Also, your client's won't think that you don't trust them. A fixed evaluation period in the application is extremely common.

Provide them a VMware image without any user-access just allow them to open the website externally via HTTP in their web browser.

Get original url without non-standard port (C#)

First question!
Environment
MVC, C#, AppHarbor.
Problem
I am calling an openid provider, and generating an absolute callback url based on the domain.
On my local machine, this works fine if I hit http://localhost:12345/login
Request.Url; //gives me `http://localhost:12345/callback`
However, on AppHarbor where I'm deploying, because they are using non-standard ports, even if I'm hitting it at "http://sub.example.com/login"
Request.Url; //gives me http://sub.example.com:15232/callback
And this screws up my callback, because the port number wasn't in the original source url!
I've tried
Request.Url
Request.Url.OriginalString
Request.RawUrl
All gives me "http://sub.example.com:15232/callback".
Also to clear up that this isn't a Realm issue, the error message I am getting from DotNetOpenAuth is
'http://sub.example.com:14107/accounts/openidcallback' not under realm 'http://*.example.com/'.
I don't think I've stuffed that up?
Now, I'm about to consider some hacky stuff like
preprocessor commands (#IF DEBUG THEN PUT PORT)
string replace (Request.URL.Contains("localhost"))
All of these are not 100% solutions, but I'm sick of mulling over what could be a simple property that I am missing. I have also read this but that doesn't seem to have an accepted answer (and is more about the path rather than the authority). So I'm putting it towards you guys.
Summary
So if I had http://localhost:12345/login, I need to get http://localhost:12345/callback from the Request context.
And if I had "http://sub.example.com/login", I should get "http://sub.example.com/callback", regardless of what port it is on.
Thanks! (Sleep time, will answer any questions in the morning)

This is a common problem in load balanced setups like AppHarbor's - we've provided an example workaround.
Update: A more desirable solution for many ASP.NET applications may be to set the aspnet:UseHostHeaderForRequestUrl appSetting to true. We (AppHarbor) have seen several customers experience issues using it with their WCF apps, which is why we haven't enabled it by default and stil recommend the above solution for those situations. You can configure it using AppHarbor's "Configuration Variables" to inject the appsettings when deployed. More information can be found in this article.

I recently ran into an issue where I compared a URL to the current URL, and then highlighted navigation based on that. It worked locally, but not in production.
I had http://example.com/path/to/file.aspx as my file, but when viewing that file and running Request.Url.ToString() it produced https://example.com:81/path/to/file.aspx in a load balanced production environment.
Now I am using Request.Url.AbsolutePath to just give me /path/to/file.aspx, thus ignoring the schema, hostname, and port numbers.
When I need to compare it to the URL on each navigation item I used:
New Uri(theLink.Href).AbsolutePath

My initial thoughts are get the referrer variable and check if that includes a port, if so use it otherwise don't.
If that’s not an option because a proxy might remove the referrer header variable then you might need to use some client side script to get the location and pass it back to the server.
I'm guessing that AppHarbor use port forwarding to the IIS server so even though publicly the site is on port 80 IIS has it hosted on another port so it can't know what port the client connected on.

Something like
String port = Request.ServerVariables["SERVER_PORT"] == "80" ? "" : ":" + Request.ServerVariables["SERVER_PORT"];
String virtualRoot = Url.Content("~/");
destinationUrl = String.Format("http://{0}{1}{2}", Request.ServerVariables["SERVER_NAME"], port + virtualRoot, "/callback");

If you use the UrlBuilder class in the framework you can easly get around this. On the builder class if you set the port to -1 then the port number will be removed:
new UriBuilder("http://sub.example.com:15232/callback"){ Port = -1}
returns : http://sub.example.com/callback
To keep the port number on a local machine just check Request.IsLocal and don't apply -1 to the port.
I would wrap this into a extension method to keep it clean.

I see that this is an old thread. I had this issue running MVC5, on IIS 7.5, with an Apache proxy in front. Outside of the server, I would get "Empty Response", since the asp.net app gets the Url from apache with the custom port.
In order to have the app redirect to a subpath without including the "custom" port, forget the Response/Request objects, and use the Transfer method. For instance, if I want that users are automatically redirected to the login page in case they are not logged already:
if (!User.Identity.IsAuthenticated)
Server.TransferRequest("Account/Login");

Can I temporarily override DNS resolution within a .NET application?

I have some wrapper code that runs a set of NUnit tests that scan live websites for certain response codes.
I'd like to run these tests against a different server. When running manually, I can do this by editing the /etc/hosts file in Windows\System32\drivers and temporarily setting www.mysite.com to 10.0.0.whatever
Is there any way I can do the same within a .NET console application - temporarily override a DNS record or somehow intercept the resolution and return a different IP address?
EDIT: This is for testing multiple servers in a web farm. I have three live servers, all of which THINK they are www.example.com. Because the servers use HTTP host headers, I can't just run a test against server1, then server2, then server3, because an HTTP request to http://server1/ will NOT return the same thing as a request to http://www.example.com/ that's resolved to server1...

In the past with C++ I was able to hook to the WSOCK32.DLL's gethostbyname function and reroute DNS requests. I used the Microsoft Detours library to do that.
As for C# I found this: http://easyhook.codeplex.com/ maybe it will help you. Basically you can hook to the gethostbyname windows function and execute your own code or return a different result (different IP).
The other possible solution is to temporarily (and programatically) edit the hosts file when the application starts and ends. From your own code.
EDIT: I found my old C++ code, maybe it will give you a hint what to do.
struct hostent FAR * WSAAPI MyGetHostByName(IN const char FAR * name)
{
// Call the regular function
struct hostent* ret = GetHostByNameFunction(name);
// Check if it's the hostname you want to reroute
if ( strcmp(host, (char*)name) == 0 )
{
// Edit the IP returned by the regular gethostbyname
ret->h_addr_list[0] = hostIP;
ret->h_length = 15;
}
// Return the result
return ret;
}
EDIT2: Found another link with newer release of easyhooks

Custom API requirement

We are currently working on an API for an existing system.
It basically wraps some web-requests as an easy-to-use library that 3rd party companies should be able to use with our product.
As part of the API, there is an event mechanism where the server can call back to the client via a constantly-running socket connection.
To minimize load on the server, we want to only have one connection per computer. Currently there is a socket open per process, and that could eventually cause load problems if you had multiple applications using the API.
So my question is: if we want to deploy our API as a single standalone assembly, what is the best way to fix our problem?
A couple options we thought of:
Write an out of process COM object (don't know if that works in .Net)
Include a second exe file that would be required for events, it would have to single-instance itself, and open a named pipe or something to communicate through multiple processes
Extract this exe file from an embedded resource and execute it
None of those really seem ideal.
Any better ideas?

Do you mean something like Net.TCP port sharing?

You could fix the client-side port while opening your socket, say 45534. Since one port can be opened by only one process, only one process at a time would be able to open socket connection to the server.

Well, there are many ways to solve this as expressed in all the answers and comments, but may be the simpler way you can use is just have global status store in a place accesible for all the users of the current machine (may be you might have various users logged-in on the machine) where you store WHO has the right to have this open. Something like a "lock" as is used to be called. That store can be a field in a local or intranet database, a simple file, or whatever. That way you don't need to build or distribute extra binaries.

When a client connects to your server you create a new thread to handle him (not a process). You can store his IP address in a static dictionary (shared between all threads).
Something like:
static Dictionary<string, TcpClient> clients = new Dictionary<string, TcpClient>();
//This method is executed in a thread
void ProcessRequest(TcpClient client)
{
string ip = null;
//TODO: get client IP address
lock (clients)
{
...
if (clients.ContainsKey(ip))
{
//TODO: Deny connection
return;
}
else
{
clients.Add(ip, client);
}
}
//TODO: Answer the client
}
//TODO: Delete client from list on disconnection

The best solution we've come up with is to create a windows service that opens up a named pipe to manage multiple client processes through one socket connection to the server.
Then our API will be able to detect if the service is running/installed and fall back to creating it's own connection for the client otherwise.
3rd parties can decide if they want to bundle the service with their product or not, but core applications from our system will have it installed.
I will mark this as the answer in a few days if no one has a better option. I was hoping there was a way to execute our assembly as a new process, but all roads to do this do not seem very reliable.