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• How to set which IP to use for a HTTP request?

  - by GetFree

  This is probably a silly question. I'm doing some http requests using wget from the command line, and I want those connections to be made through one specific IP of the 4 IPs my server has. Those http requests go to one specific range of IPs so I only want those to be routed differently. The 4 interfaces in my server are eth0, eth0:0, eth0:1, eth0:2. I tried with the following command: route add -net 192.164.10.0/24 dev eth0:0 But when I see the routing table it says: Destination Gateway Genmask Flags MSS Window irtt Iface 192.164.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 The interface is set to eth0 not eth0:0 as my command says. What am I doing wrong?

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• How to know that my IP is invalid

  - by PeterMmm

  I have a script running that will start up an interface with a new IP. If the script comes up with an IP that is already in use i am in trouble. Is it possible that the script set up the new Ip, detects that this IP is already in use and then check the next one, until it finds an ip that works ? B=192.168.1. I=1 while [ "$I" != "256" ] do ifconfig eth0:1 $B.$I # check here that IP is Ok ! let "I=I+1" done

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• Should I still use querystrings for page number, etc, when using ASP.NET 4 URL Routing?

  - by Scott

  I am switching from Intelligencia's UrlRewriter to the new web forms routing in ASP.NET 4.0. I have it working great for basic pages, however, in my e-commerce site, when browsing category pages, I previously used querystrings that were built into my pager control to control paging. An old url (with UrlRewriting) would be: http://www.mysite.com/Category/Arts-and-Crafts_17 I now have a MapPageRoute defined in global.asax as: routes.MapPageRoute("category-browse", "Category/{name}_{id}", ~/CategoryPage.aspx"); This works great. Now, somebody clicks to go to page 2. Previously I would have just tacked on ?page=2 as the querystring. Now, How do I handle this using web forms routing? I know I can do something like: http://www.mysite.com/Category/Arts-and-Crafts_17/page/2 But in addition to page, I can have filters, age ranges, gender, etc. Should I just keep defining routes that handle these variables, or should I continue using querystrings and can I define a route that allows me to use my querstrings like before?

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• An Introduction to ASP.NET Web API

  - by Rick Strahl

  Microsoft recently released ASP.NET MVC 4.0 and .NET 4.5 and along with it, the brand spanking new ASP.NET Web API. Web API is an exciting new addition to the ASP.NET stack that provides a new, well-designed HTTP framework for creating REST and AJAX APIs (API is Microsoft’s new jargon for a service, in case you’re wondering). Although Web API ships and installs with ASP.NET MVC 4, you can use Web API functionality in any ASP.NET project, including WebForms, WebPages and MVC or just a Web API by itself. And you can also self-host Web API in your own applications from Console, Desktop or Service applications. If you're interested in a high level overview on what ASP.NET Web API is and how it fits into the ASP.NET stack you can check out my previous post: Where does ASP.NET Web API fit? In the following article, I'll focus on a practical, by example introduction to ASP.NET Web API. All the code discussed in this article is available in GitHub: https://github.com/RickStrahl/AspNetWebApiArticle [republished from my Code Magazine Article and updated for RTM release of ASP.NET Web API] Getting Started To start I’ll create a new empty ASP.NET application to demonstrate that Web API can work with any kind of ASP.NET project. Although you can create a new project based on the ASP.NET MVC/Web API template to quickly get up and running, I’ll take you through the manual setup process, because one common use case is to add Web API functionality to an existing ASP.NET application. This process describes the steps needed to hook up Web API to any ASP.NET 4.0 application. Start by creating an ASP.NET Empty Project. Then create a new folder in the project called Controllers. Add a Web API Controller Class Once you have any kind of ASP.NET project open, you can add a Web API Controller class to it. Web API Controllers are very similar to MVC Controller classes, but they work in any kind of project. Add a new item to this folder by using the Add New Item option in Visual Studio and choose Web API Controller Class, as shown in Figure 1. Figure 1: This is how you create a new Controller Class in Visual Studio   Make sure that the name of the controller class includes Controller at the end of it, which is required in order for Web API routing to find it. Here, the name for the class is AlbumApiController. For this example, I’ll use a Music Album model to demonstrate basic behavior of Web API. The model consists of albums and related songs where an album has properties like Name, Artist and YearReleased and a list of songs with a SongName and SongLength as well as an AlbumId that links it to the album. You can find the code for the model (and the rest of these samples) on Github. To add the file manually, create a new folder called Model, and add a new class Album.cs and copy the code into it. There’s a static AlbumData class with a static CreateSampleAlbumData() method that creates a short list of albums on a static .Current that I’ll use for the examples. Before we look at what goes into the controller class though, let’s hook up routing so we can access this new controller. Hooking up Routing in Global.asax To start, I need to perform the one required configuration task in order for Web API to work: I need to configure routing to the controller. Like MVC, Web API uses routing to provide clean, extension-less URLs to controller methods. Using an extension method to ASP.NET’s static RouteTable class, you can use the MapHttpRoute() (in the System.Web.Http namespace) method to hook-up the routing during Application_Start in global.asax.cs shown in Listing 1.using System; using System.Web.Routing; using System.Web.Http; namespace AspNetWebApi { public class Global : System.Web.HttpApplication { protected void Application_Start(object sender, EventArgs e) { RouteTable.Routes.MapHttpRoute( name: "AlbumVerbs", routeTemplate: "albums/{title}", defaults: new { symbol = RouteParameter.Optional, controller="AlbumApi" } ); } } } This route configures Web API to direct URLs that start with an albums folder to the AlbumApiController class. Routing in ASP.NET is used to create extensionless URLs and allows you to map segments of the URL to specific Route Value parameters. A route parameter, with a name inside curly brackets like {name}, is mapped to parameters on the controller methods. Route parameters can be optional, and there are two special route parameters – controller and action – that determine the controller to call and the method to activate respectively. HTTP Verb Routing Routing in Web API can route requests by HTTP Verb in addition to standard {controller},{action} routing. For the first examples, I use HTTP Verb routing, as shown Listing 1. Notice that the route I’ve defined does not include an {action} route value or action value in the defaults. Rather, Web API can use the HTTP Verb in this route to determine the method to call the controller, and a GET request maps to any method that starts with Get. So methods called Get() or GetAlbums() are matched by a GET request and a POST request maps to a Post() or PostAlbum(). Web API matches a method by name and parameter signature to match a route, query string or POST values. In lieu of the method name, the [HttpGet,HttpPost,HttpPut,HttpDelete, etc] attributes can also be used to designate the accepted verbs explicitly if you don’t want to follow the verb naming conventions. Although HTTP Verb routing is a good practice for REST style resource APIs, it’s not required and you can still use more traditional routes with an explicit {action} route parameter. When {action} is supplied, the HTTP verb routing is ignored. I’ll talk more about alternate routes later. When you’re finished with initial creation of files, your project should look like Figure 2.   Figure 2: The initial project has the new API Controller Album model   Creating a small Album Model Now it’s time to create some controller methods to serve data. For these examples, I’ll use a very simple Album and Songs model to play with, as shown in Listing 2. public class Song { public string AlbumId { get; set; } [Required, StringLength(80)] public string SongName { get; set; } [StringLength(5)] public string SongLength { get; set; } } public class Album { public string Id { get; set; } [Required, StringLength(80)] public string AlbumName { get; set; } [StringLength(80)] public string Artist { get; set; } public int YearReleased { get; set; } public DateTime Entered { get; set; } [StringLength(150)] public string AlbumImageUrl { get; set; } [StringLength(200)] public string AmazonUrl { get; set; } public virtual List<Song> Songs { get; set; } public Album() { Songs = new List<Song>(); Entered = DateTime.Now; // Poor man's unique Id off GUID hash Id = Guid.NewGuid().GetHashCode().ToString("x"); } public void AddSong(string songName, string songLength = null) { this.Songs.Add(new Song() { AlbumId = this.Id, SongName = songName, SongLength = songLength }); } } Once the model has been created, I also added an AlbumData class that generates some static data in memory that is loaded onto a static .Current member. The signature of this class looks like this and that's what I'll access to retrieve the base data:public static class AlbumData { // sample data - static list public static List<Album> Current = CreateSampleAlbumData(); /// <summary> /// Create some sample data /// </summary> /// <returns></returns> public static List<Album> CreateSampleAlbumData() { … }} You can check out the full code for the data generation online. Creating an AlbumApiController Web API shares many concepts of ASP.NET MVC, and the implementation of your API logic is done by implementing a subclass of the System.Web.Http.ApiController class. Each public method in the implemented controller is a potential endpoint for the HTTP API, as long as a matching route can be found to invoke it. The class name you create should end in Controller, which is how Web API matches the controller route value to figure out which class to invoke. Inside the controller you can implement methods that take standard .NET input parameters and return .NET values as results. Web API’s binding tries to match POST data, route values, form values or query string values to your parameters. Because the controller is configured for HTTP Verb based routing (no {action} parameter in the route), any methods that start with Getxxxx() are called by an HTTP GET operation. You can have multiple methods that match each HTTP Verb as long as the parameter signatures are different and can be matched by Web API. In Listing 3, I create an AlbumApiController with two methods to retrieve a list of albums and a single album by its title .public class AlbumApiController : ApiController { public IEnumerable<Album> GetAlbums() { var albums = AlbumData.Current.OrderBy(alb => alb.Artist); return albums; } public Album GetAlbum(string title) { var album = AlbumData.Current .SingleOrDefault(alb => alb.AlbumName.Contains(title)); return album; }} To access the first two requests, you can use the following URLs in your browser: http://localhost/aspnetWebApi/albumshttp://localhost/aspnetWebApi/albums/Dirty%20Deeds Note that you’re not specifying the actions of GetAlbum or GetAlbums in these URLs. Instead Web API’s routing uses HTTP GET verb to route to these methods that start with Getxxx() with the first mapping to the parameterless GetAlbums() method and the latter to the GetAlbum(title) method that receives the title parameter mapped as optional in the route. Content Negotiation When you access any of the URLs above from a browser, you get either an XML or JSON result returned back. The album list result for Chrome 17 and Internet Explorer 9 is shown Figure 3. Figure 3: Web API responses can vary depending on the browser used, demonstrating Content Negotiation in action as these two browsers send different HTTP Accept headers.   Notice that the results are not the same: Chrome returns an XML response and IE9 returns a JSON response. Whoa, what’s going on here? Shouldn’t we see the same result in both browsers? Actually, no. Web API determines what type of content to return based on Accept headers. HTTP clients, like browsers, use Accept headers to specify what kind of content they’d like to see returned. Browsers generally ask for HTML first, followed by a few additional content types. Chrome (and most other major browsers) ask for: Accept: text/html, application/xhtml+xml,application/xml; q=0.9,*/*;q=0.8 IE9 asks for: Accept: text/html, application/xhtml+xml, */* Note that Chrome’s Accept header includes application/xml, which Web API finds in its list of supported media types and returns an XML response. IE9 does not include an Accept header type that works on Web API by default, and so it returns the default format, which is JSON. This is an important and very useful feature that was missing from any previous Microsoft REST tools: Web API automatically switches output formats based on HTTP Accept headers. Nowhere in the server code above do you have to explicitly specify the output format. Rather, Web API determines what format the client is requesting based on the Accept headers and automatically returns the result based on the available formatters. This means that a single method can handle both XML and JSON results.. Using this simple approach makes it very easy to create a single controller method that can return JSON, XML, ATOM or even OData feeds by providing the appropriate Accept header from the client. By default you don’t have to worry about the output format in your code. Note that you can still specify an explicit output format if you choose, either globally by overriding the installed formatters, or individually by returning a lower level HttpResponseMessage instance and setting the formatter explicitly. More on that in a minute. Along the same lines, any content sent to the server via POST/PUT is parsed by Web API based on the HTTP Content-type of the data sent. The same formats allowed for output are also allowed on input. Again, you don’t have to do anything in your code – Web API automatically performs the deserialization from the content. Accessing Web API JSON Data with jQuery A very common scenario for Web API endpoints is to retrieve data for AJAX calls from the Web browser. Because JSON is the default format for Web API, it’s easy to access data from the server using jQuery and its getJSON() method. This example receives the albums array from GetAlbums() and databinds it into the page using knockout.js.$.getJSON("albums/", function (albums) { // make knockout template visible $(".album").show(); // create view object and attach array var view = { albums: albums }; ko.applyBindings(view); }); Figure 4 shows this and the next example’s HTML output. You can check out the complete HTML and script code at http://goo.gl/Ix33C (.html) and http://goo.gl/tETlg (.js). Figu Figure 4: The Album Display sample uses JSON data loaded from Web API.   The result from the getJSON() call is a JavaScript object of the server result, which comes back as a JavaScript array. In the code, I use knockout.js to bind this array into the UI, which as you can see, requires very little code, instead using knockout’s data-bind attributes to bind server data to the UI. Of course, this is just one way to use the data – it’s entirely up to you to decide what to do with the data in your client code. Along the same lines, I can retrieve a single album to display when the user clicks on an album. The response returns the album information and a child array with all the songs. The code to do this is very similar to the last example where we pulled the albums array:$(".albumlink").live("click", function () { var id = $(this).data("id"); // title $.getJSON("albums/" + id, function (album) { ko.applyBindings(album, $("#divAlbumDialog")[0]); $("#divAlbumDialog").show(); }); }); Here the URL looks like this: /albums/Dirty%20Deeds, where the title is the ID captured from the clicked element’s data ID attribute. Explicitly Overriding Output Format When Web API automatically converts output using content negotiation, it does so by matching Accept header media types to the GlobalConfiguration.Configuration.Formatters and the SupportedMediaTypes of each individual formatter. You can add and remove formatters to globally affect what formats are available and it’s easy to create and plug in custom formatters.The example project includes a JSONP formatter that can be plugged in to provide JSONP support for requests that have a callback= querystring parameter. Adding, removing or replacing formatters is a global option you can use to manipulate content. It’s beyond the scope of this introduction to show how it works, but you can review the sample code or check out my blog entry on the subject (http://goo.gl/UAzaR). If automatic processing is not desirable in a particular Controller method, you can override the response output explicitly by returning an HttpResponseMessage instance. HttpResponseMessage is similar to ActionResult in ASP.NET MVC in that it’s a common way to return an abstract result message that contains content. HttpResponseMessage s parsed by the Web API framework using standard interfaces to retrieve the response data, status code, headers and so on[MS2] . Web API turns every response – including those Controller methods that return static results – into HttpResponseMessage instances. Explicitly returning an HttpResponseMessage instance gives you full control over the output and lets you mostly bypass WebAPI’s post-processing of the HTTP response on your behalf. HttpResponseMessage allows you to customize the response in great detail. Web API’s attention to detail in the HTTP spec really shows; many HTTP options are exposed as properties and enumerations with detailed IntelliSense comments. Even if you’re new to building REST-based interfaces, the API guides you in the right direction for returning valid responses and response codes. For example, assume that I always want to return JSON from the GetAlbums() controller method and ignore the default media type content negotiation. To do this, I can adjust the output format and headers as shown in Listing 4.public HttpResponseMessage GetAlbums() { var albums = AlbumData.Current.OrderBy(alb => alb.Artist); // Create a new HttpResponse with Json Formatter explicitly var resp = new HttpResponseMessage(HttpStatusCode.OK); resp.Content = new ObjectContent<IEnumerable<Album>>( albums, new JsonMediaTypeFormatter()); // Get Default Formatter based on Content Negotiation //var resp = Request.CreateResponse<IEnumerable<Album>>(HttpStatusCode.OK, albums); resp.Headers.ConnectionClose = true; resp.Headers.CacheControl = new CacheControlHeaderValue(); resp.Headers.CacheControl.Public = true; return resp; } This example returns the same IEnumerable<Album> value, but it wraps the response into an HttpResponseMessage so you can control the entire HTTP message result including the headers, formatter and status code. In Listing 4, I explicitly specify the formatter using the JsonMediaTypeFormatter to always force the content to JSON.  If you prefer to use the default content negotiation with HttpResponseMessage results, you can create the Response instance using the Request.CreateResponse method:var resp = Request.CreateResponse<IEnumerable<Album>>(HttpStatusCode.OK, albums); This provides you an HttpResponse object that's pre-configured with the default formatter based on Content Negotiation. Once you have an HttpResponse object you can easily control most HTTP aspects on this object. What's sweet here is that there are many more detailed properties on HttpResponse than the core ASP.NET Response object, with most options being explicitly configurable with enumerations that make it easy to pick the right headers and response codes from a list of valid codes. It makes HTTP features available much more discoverable even for non-hardcore REST/HTTP geeks. Non-Serialized Results The output returned doesn’t have to be a serialized value but can also be raw data, like strings, binary data or streams. You can use the HttpResponseMessage.Content object to set a number of common Content classes. Listing 5 shows how to return a binary image using the ByteArrayContent class from a Controller method. [HttpGet] public HttpResponseMessage AlbumArt(string title) { var album = AlbumData.Current.FirstOrDefault(abl => abl.AlbumName.StartsWith(title)); if (album == null) { var resp = Request.CreateResponse<ApiMessageError>( HttpStatusCode.NotFound, new ApiMessageError("Album not found")); return resp; } // kinda silly - we would normally serve this directly // but hey - it's a demo. var http = new WebClient(); var imageData = http.DownloadData(album.AlbumImageUrl); // create response and return var result = new HttpResponseMessage(HttpStatusCode.OK); result.Content = new ByteArrayContent(imageData); result.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpeg"); return result; } The image retrieval from Amazon is contrived, but it shows how to return binary data using ByteArrayContent. It also demonstrates that you can easily return multiple types of content from a single controller method, which is actually quite common. If an error occurs - such as a resource can’t be found or a validation error – you can return an error response to the client that’s very specific to the error. In GetAlbumArt(), if the album can’t be found, we want to return a 404 Not Found status (and realistically no error, as it’s an image). Note that if you are not using HTTP Verb-based routing or not accessing a method that starts with Get/Post etc., you have to specify one or more HTTP Verb attributes on the method explicitly. Here, I used the [HttpGet] attribute to serve the image. Another option to handle the error could be to return a fixed placeholder image if no album could be matched or the album doesn’t have an image. When returning an error code, you can also return a strongly typed response to the client. For example, you can set the 404 status code and also return a custom error object (ApiMessageError is a class I defined) like this:return Request.CreateResponse<ApiMessageError>( HttpStatusCode.NotFound, new ApiMessageError("Album not found") );   If the album can be found, the image will be returned. The image is downloaded into a byte[] array, and then assigned to the result’s Content property. I created a new ByteArrayContent instance and assigned the image’s bytes and the content type so that it displays properly in the browser. There are other content classes available: StringContent, StreamContent, ByteArrayContent, MultipartContent, and ObjectContent are at your disposal to return just about any kind of content. You can create your own Content classes if you frequently return custom types and handle the default formatter assignments that should be used to send the data out . Although HttpResponseMessage results require more code than returning a plain .NET value from a method, it allows much more control over the actual HTTP processing than automatic processing. It also makes it much easier to test your controller methods as you get a response object that you can check for specific status codes and output messages rather than just a result value. Routing Again Ok, let’s get back to the image example. Using the original routing we have setup using HTTP Verb routing there's no good way to serve the image. In order to return my album art image I’d like to use a URL like this: http://localhost/aspnetWebApi/albums/Dirty%20Deeds/image In order to create a URL like this, I have to create a new Controller because my earlier routes pointed to the AlbumApiController using HTTP Verb routing. HTTP Verb based routing is great for representing a single set of resources such as albums. You can map operations like add, delete, update and read easily using HTTP Verbs. But you cannot mix action based routing into a an HTTP Verb routing controller - you can only map HTTP Verbs and each method has to be unique based on parameter signature. You can't have multiple GET operations to methods with the same signature. So GetImage(string id) and GetAlbum(string title) are in conflict in an HTTP GET routing scenario. In fact, I was unable to make the above Image URL work with any combination of HTTP Verb plus Custom routing using the single Albums controller. There are number of ways around this, but all involve additional controllers.  Personally, I think it’s easier to use explicit Action routing and then add custom routes if you need to simplify your URLs further. So in order to accommodate some of the other examples, I created another controller – AlbumRpcApiController – to handle all requests that are explicitly routed via actions (/albums/rpc/AlbumArt) or are custom routed with explicit routes defined in the HttpConfiguration. I added the AlbumArt() method to this new AlbumRpcApiController class. For the image URL to work with the new AlbumRpcApiController, you need a custom route placed before the default route from Listing 1.RouteTable.Routes.MapHttpRoute( name: "AlbumRpcApiAction", routeTemplate: "albums/rpc/{action}/{title}", defaults: new { title = RouteParameter.Optional, controller = "AlbumRpcApi", action = "GetAblums" } ); Now I can use either of the following URLs to access the image: Custom route: (/albums/rpc/{title}/image)http://localhost/aspnetWebApi/albums/PowerAge/image Action route: (/albums/rpc/action/{title})http://localhost/aspnetWebAPI/albums/rpc/albumart/PowerAge Sending Data to the Server To send data to the server and add a new album, you can use an HTTP POST operation. Since I’m using HTTP Verb-based routing in the original AlbumApiController, I can implement a method called PostAlbum()to accept a new album from the client. Listing 6 shows the Web API code to add a new album.public HttpResponseMessage PostAlbum(Album album) { if (!this.ModelState.IsValid) { // my custom error class var error = new ApiMessageError() { message = "Model is invalid" }; // add errors into our client error model for client foreach (var prop in ModelState.Values) { var modelError = prop.Errors.FirstOrDefault(); if (!string.IsNullOrEmpty(modelError.ErrorMessage)) error.errors.Add(modelError.ErrorMessage); else error.errors.Add(modelError.Exception.Message); } return Request.CreateResponse<ApiMessageError>(HttpStatusCode.Conflict, error); } // update song id which isn't provided foreach (var song in album.Songs) song.AlbumId = album.Id; // see if album exists already var matchedAlbum = AlbumData.Current .SingleOrDefault(alb => alb.Id == album.Id || alb.AlbumName == album.AlbumName); if (matchedAlbum == null) AlbumData.Current.Add(album); else matchedAlbum = album; // return a string to show that the value got here var resp = Request.CreateResponse(HttpStatusCode.OK, string.Empty); resp.Content = new StringContent(album.AlbumName + " " + album.Entered.ToString(), Encoding.UTF8, "text/plain"); return resp; } The PostAlbum() method receives an album parameter, which is automatically deserialized from the POST buffer the client sent. The data passed from the client can be either XML or JSON. Web API automatically figures out what format it needs to deserialize based on the content type and binds the content to the album object. Web API uses model binding to bind the request content to the parameter(s) of controller methods. Like MVC you can check the model by looking at ModelState.IsValid. If it’s not valid, you can run through the ModelState.Values collection and check each binding for errors. Here I collect the error messages into a string array that gets passed back to the client via the result ApiErrorMessage object. When a binding error occurs, you’ll want to return an HTTP error response and it’s best to do that with an HttpResponseMessage result. In Listing 6, I used a custom error class that holds a message and an array of detailed error messages for each binding error. I used this object as the content to return to the client along with my Conflict HTTP Status Code response. If binding succeeds, the example returns a string with the name and date entered to demonstrate that you captured the data. Normally, a method like this should return a Boolean or no response at all (HttpStatusCode.NoConent). The sample uses a simple static list to hold albums, so once you’ve added the album using the Post operation, you can hit the /albums/ URL to see that the new album was added. The client jQuery code to call the POST operation from the client with jQuery is shown in Listing 7. var id = new Date().getTime().toString(); var album = { "Id": id, "AlbumName": "Power Age", "Artist": "AC/DC", "YearReleased": 1977, "Entered": "2002-03-11T18:24:43.5580794-10:00", "AlbumImageUrl": http://ecx.images-amazon.com/images/…, "AmazonUrl": http://www.amazon.com/…, "Songs": [ { "SongName": "Rock 'n Roll Damnation", "SongLength": 3.12}, { "SongName": "Downpayment Blues", "SongLength": 4.22 }, { "SongName": "Riff Raff", "SongLength": 2.42 } ] } $.ajax( { url: "albums/", type: "POST", contentType: "application/json", data: JSON.stringify(album), processData: false, beforeSend: function (xhr) { // not required since JSON is default output xhr.setRequestHeader("Accept", "application/json"); }, success: function (result) { // reload list of albums page.loadAlbums(); }, error: function (xhr, status, p3, p4) { var err = "Error"; if (xhr.responseText && xhr.responseText[0] == "{") err = JSON.parse(xhr.responseText).message; alert(err); } }); The code in Listing 7 creates an album object in JavaScript to match the structure of the .NET Album class. This object is passed to the $.ajax() function to send to the server as POST. The data is turned into JSON and the content type set to application/json so that the server knows what to convert when deserializing in the Album instance. The jQuery code hooks up success and failure events. Success returns the result data, which is a string that’s echoed back with an alert box. If an error occurs, jQuery returns the XHR instance and status code. You can check the XHR to see if a JSON object is embedded and if it is, you can extract it by de-serializing it and accessing the .message property. REST standards suggest that updates to existing resources should use PUT operations. REST standards aside, I’m not a big fan of separating out inserts and updates so I tend to have a single method that handles both. But if you want to follow REST suggestions, you can create a PUT method that handles updates by forwarding the PUT operation to the POST method:public HttpResponseMessage PutAlbum(Album album) { return PostAlbum(album); } To make the corresponding $.ajax() call, all you have to change from Listing 7 is the type: from POST to PUT. Model Binding with UrlEncoded POST Variables In the example in Listing 7 I used JSON objects to post a serialized object to a server method that accepted an strongly typed object with the same structure, which is a common way to send data to the server. However, Web API supports a number of different ways that data can be received by server methods. For example, another common way is to use plain UrlEncoded POST  values to send to the server. Web API supports Model Binding that works similar (but not the same) as MVC's model binding where POST variables are mapped to properties of object parameters of the target method. This is actually quite common for AJAX calls that want to avoid serialization and the potential requirement of a JSON parser on older browsers. For example, using jQUery you might use the $.post() method to send a new album to the server (albeit one without songs) using code like the following:$.post("albums/",{AlbumName: "Dirty Deeds", YearReleased: 1976 … },albumPostCallback); Although the code looks very similar to the client code we used before passing JSON, here the data passed is URL encoded values (AlbumName=Dirty+Deeds&YearReleased=1976 etc.). Web API then takes this POST data and maps each of the POST values to the properties of the Album object in the method's parameter. Although the client code is different the server can both handle the JSON object, or the UrlEncoded POST values. Dynamic Access to POST Data There are also a few options available to dynamically access POST data, if you know what type of data you're dealing with. If you have POST UrlEncoded values, you can dynamically using a FormsDataCollection:[HttpPost] public string PostAlbum(FormDataCollection form) { return string.Format("{0} - released {1}", form.Get("AlbumName"),form.Get("RearReleased")); } The FormDataCollection is a very simple object, that essentially provides the same functionality as Request.Form[] in ASP.NET. Request.Form[] still works if you're running hosted in an ASP.NET application. However as a general rule, while ASP.NET's functionality is always available when running Web API hosted inside of an  ASP.NET application, using the built in classes specific to Web API makes it possible to run Web API applications in a self hosted environment outside of ASP.NET. If your client is sending JSON to your server, and you don't want to map the JSON to a strongly typed object because you only want to retrieve a few simple values, you can also accept a JObject parameter in your API methods:[HttpPost] public string PostAlbum(JObject jsonData) { dynamic json = jsonData; JObject jalbum = json.Album; JObject juser = json.User; string token = json.UserToken; var album = jalbum.ToObject<Album>(); var user = juser.ToObject<User>(); return String.Format("{0} {1} {2}", album.AlbumName, user.Name, token); } There quite a few options available to you to receive data with Web API, which gives you more choices for the right tool for the job. Unfortunately one shortcoming of Web API is that POST data is always mapped to a single parameter. This means you can't pass multiple POST parameters to methods that receive POST data. It's possible to accept multiple parameters, but only one can map to the POST content - the others have to come from the query string or route values. I have a couple of Blog POSTs that explain what works and what doesn't here: Passing multiple POST parameters to Web API Controller Methods Mapping UrlEncoded POST Values in ASP.NET Web API   Handling Delete Operations Finally, to round out the server API code of the album example we've been discussin, here’s the DELETE verb controller method that allows removal of an album by its title:public HttpResponseMessage DeleteAlbum(string title) { var matchedAlbum = AlbumData.Current.Where(alb => alb.AlbumName == title) .SingleOrDefault(); if (matchedAlbum == null) return new HttpResponseMessage(HttpStatusCode.NotFound); AlbumData.Current.Remove(matchedAlbum); return new HttpResponseMessage(HttpStatusCode.NoContent); } To call this action method using jQuery, you can use:$(".removeimage").live("click", function () { var $el = $(this).parent(".album"); var txt = $el.find("a").text(); $.ajax({ url: "albums/" + encodeURIComponent(txt), type: "Delete", success: function (result) { $el.fadeOut().remove(); }, error: jqError }); }   Note the use of the DELETE verb in the $.ajax() call, which routes to DeleteAlbum on the server. DELETE is a non-content operation, so you supply a resource ID (the title) via route value or the querystring. Routing Conflicts In all requests with the exception of the AlbumArt image example shown so far, I used HTTP Verb routing that I set up in Listing 1. HTTP Verb Routing is a recommendation that is in line with typical REST access to HTTP resources. However, it takes quite a bit of effort to create REST-compliant API implementations based only on HTTP Verb routing only. You saw one example that didn’t really fit – the return of an image where I created a custom route albums/{title}/image that required creation of a second controller and a custom route to work. HTTP Verb routing to a controller does not mix with custom or action routing to the same controller because of the limited mapping of HTTP verbs imposed by HTTP Verb routing. To understand some of the problems with verb routing, let’s look at another example. Let’s say you create a GetSortableAlbums() method like this and add it to the original AlbumApiController accessed via HTTP Verb routing:[HttpGet] public IQueryable<Album> SortableAlbums() { var albums = AlbumData.Current; // generally should be done only on actual queryable results (EF etc.) // Done here because we're running with a static list but otherwise might be slow return albums.AsQueryable(); } If you compile this code and try to now access the /albums/ link, you get an error: Multiple Actions were found that match the request. HTTP Verb routing only allows access to one GET operation per parameter/route value match. If more than one method exists with the same parameter signature, it doesn’t work. As I mentioned earlier for the image display, the only solution to get this method to work is to throw it into another controller. Because I already set up the AlbumRpcApiController I can add the method there. First, I should rename the method to SortableAlbums() so I’m not using a Get prefix for the method. This also makes the action parameter look cleaner in the URL - it looks less like a method and more like a noun. I can then create a new route that handles direct-action mapping:RouteTable.Routes.MapHttpRoute( name: "AlbumRpcApiAction", routeTemplate: "albums/rpc/{action}/{title}", defaults: new { title = RouteParameter.Optional, controller = "AlbumRpcApi", action = "GetAblums" } ); As I am explicitly adding a route segment – rpc – into the route template, I can now reference explicit methods in the Web API controller using URLs like this: http://localhost/AspNetWebApi/rpc/SortableAlbums Error Handling I’ve already done some minimal error handling in the examples. For example in Listing 6, I detected some known-error scenarios like model validation failing or a resource not being found and returning an appropriate HttpResponseMessage result. But what happens if your code just blows up or causes an exception? If you have a controller method, like this:[HttpGet] public void ThrowException() { throw new UnauthorizedAccessException("Unauthorized Access Sucka"); } You can call it with this: http://localhost/AspNetWebApi/albums/rpc/ThrowException The default exception handling displays a 500-status response with the serialized exception on the local computer only. When you connect from a remote computer, Web API throws back a 500  HTTP Error with no data returned (IIS then adds its HTML error page). The behavior is configurable in the GlobalConfiguration:GlobalConfiguration .Configuration .IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Never; If you want more control over your error responses sent from code, you can throw explicit error responses yourself using HttpResponseException. When you throw an HttpResponseException the response parameter is used to generate the output for the Controller action. [HttpGet] public void ThrowError() { var resp = Request.CreateResponse<ApiMessageError>( HttpStatusCode.BadRequest, new ApiMessageError("Your code stinks!")); throw new HttpResponseException(resp); } Throwing an HttpResponseException stops the processing of the controller method and immediately returns the response you passed to the exception. Unlike other Exceptions fired inside of WebAPI, HttpResponseException bypasses the Exception Filters installed and instead just outputs the response you provide. In this case, the serialized ApiMessageError result string is returned in the default serialization format – XML or JSON. You can pass any content to HttpResponseMessage, which includes creating your own exception objects and consistently returning error messages to the client. Here’s a small helper method on the controller that you might use to send exception info back to the client consistently:private void ThrowSafeException(string message, HttpStatusCode statusCode = HttpStatusCode.BadRequest) { var errResponse = Request.CreateResponse<ApiMessageError>(statusCode, new ApiMessageError() { message = message }); throw new HttpResponseException(errResponse); } You can then use it to output any captured errors from code:[HttpGet] public void ThrowErrorSafe() { try { List<string> list = null; list.Add("Rick"); } catch (Exception ex) { ThrowSafeException(ex.Message); } }   Exception Filters Another more global solution is to create an Exception Filter. Filters in Web API provide the ability to pre- and post-process controller method operations. An exception filter looks at all exceptions fired and then optionally creates an HttpResponseMessage result. Listing 8 shows an example of a basic Exception filter implementation.public class UnhandledExceptionFilter : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { HttpStatusCode status = HttpStatusCode.InternalServerError; var exType = context.Exception.GetType(); if (exType == typeof(UnauthorizedAccessException)) status = HttpStatusCode.Unauthorized; else if (exType == typeof(ArgumentException)) status = HttpStatusCode.NotFound; var apiError = new ApiMessageError() { message = context.Exception.Message }; // create a new response and attach our ApiError object // which now gets returned on ANY exception result var errorResponse = context.Request.CreateResponse<ApiMessageError>(status, apiError); context.Response = errorResponse; base.OnException(context); } } Exception Filter Attributes can be assigned to an ApiController class like this:[UnhandledExceptionFilter] public class AlbumRpcApiController : ApiController or you can globally assign it to all controllers by adding it to the HTTP Configuration's Filters collection:GlobalConfiguration.Configuration.Filters.Add(new UnhandledExceptionFilter()); The latter is a great way to get global error trapping so that all errors (short of hard IIS errors and explicit HttpResponseException errors) return a valid error response that includes error information in the form of a known-error object. Using a filter like this allows you to throw an exception as you normally would and have your filter create a response in the appropriate output format that the client expects. For example, an AJAX application can on failure expect to see a JSON error result that corresponds to the real error that occurred rather than a 500 error along with HTML error page that IIS throws up. You can even create some custom exceptions so you can differentiate your own exceptions from unhandled system exceptions - you often don't want to display error information from 'unknown' exceptions as they may contain sensitive system information or info that's not generally useful to users of your application/site. This is just one example of how ASP.NET Web API is configurable and extensible. Exception filters are just one example of how you can plug-in into the Web API request flow to modify output. Many more hooks exist and I’ll take a closer look at extensibility in Part 2 of this article in the future. Summary Web API is a big improvement over previous Microsoft REST and AJAX toolkits. The key features to its usefulness are its ease of use with simple controller based logic, familiar MVC-style routing, low configuration impact, extensibility at all levels and tight attention to exposing and making HTTP semantics easily discoverable and easy to use. Although none of the concepts used in Web API are new or radical, Web API combines the best of previous platforms into a single framework that’s highly functional, easy to work with, and extensible to boot. I think that Microsoft has hit a home run with Web API. Related Resources Where does ASP.NET Web API fit? Sample Source Code on GitHub Passing multiple POST parameters to Web API Controller Methods Mapping UrlEncoded POST Values in ASP.NET Web API Creating a JSONP Formatter for ASP.NET Web API Removing the XML Formatter from ASP.NET Web API Applications© Rick Strahl, West Wind Technologies, 2005-2012Posted in Web Api   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Customer site is out of IP addresses, they want to go from /24 to /12 netmask... Bad idea?

  - by ewwhite

  One of my client sites called to ask me to change the subnet masks of the Linux servers I manage there while they re-IP/change the netmask of their network based on a 10.0.0.x scheme. "Can you change the server netmasks from 255.255.255.0 to 255.240.0.0?" You mean, 255.255.240.0? "No, 255.240.0.0." Are you sure you need that many IP addresses? "Yeah, we never want to run out of IP addresses." A quick check against the Subnet Cheat Sheet shows: a 255.255.255.0 netmask, a /24 provides 256 hosts. It's clear to see that an organization can exhaust that number of IP addresses. a 255.240.0.0 netmask, a /12 provides 1,048,576 hosts. This is a small < 200-user site. I doubt that they'd allocate more than 400 IP addresses. I suggested something that provides fewer hosts, like a /22 or /21 (1024 and 2048 hosts, respectively), but was unable to give a specific reason against using the /12 subnet. Is there anything this customer should be concerned about? Are there any specific reasons they shouldn't use such an incredibly large mask in their environment?

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• char array split ip with strtok

  - by user1480139

  I'm trying to split a IP address like 127.0.0.1 from a file: using following C code: pch2 = strtok (ip,"."); printf("\npart 1 ip: %s",pch2); pch2 = strtok (NULL,"."); printf("\npart 2 ip: %s",pch2); And IP is a char ip[500], that containt an ip. When printing it prints 127 as part 1 but as part 2 it prints NULL? Can someone help me? EDIT: Whole function: FILE *file = fopen ("host.txt", "r"); char * pch; char * pch2; char ip[BUFFSIZE]; IPPart result; if (file != NULL) { char line [BUFFSIZE]; while(fgets(line,sizeof line,file) != NULL) { if(line[0] != '#') { //fputs(line,stdout); pch = strtok (line," "); printf ("%s\n",pch); strncpy(ip, pch, sizeof(pch)-1); ip[sizeof(pch)-1] = '\0'; //pch = strtok (line, " "); pch = strtok (NULL," "); printf("%s",pch); pch2 = strtok (ip,"."); printf("\nDeel 1 ip: %s",pch2); pch2 = strtok (NULL,"."); printf("\nDeel 2 ip: %s",pch2); //if(strcmp(pch,url) == 0) //{ // result.part1 = //} } } fclose(file); }

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• TCP packets larger than 4 KB don't get a reply from Linux

  - by pts

  I'm running Linux 3.2.51 in a virtual machine (192.168.33.15). I'm sending Ethernet frames to it. I'm writing custom software trying to emulate a TCP peer, the other peer is Linux running in the virtual machine guest. I've noticed that TCP packets larger than about 4 KB are ignored (i.e. dropped without an ACK) by the Linux guest. If I decrease the packet size by 50 bytes, I get an ACK. I'm not sending new payload data until the Linux guest fully ACKs the previous one. I've increased ifconfig eth0 mtu 51000, and ping -c 1 -s 50000 goes through (from guest to my emulator) and the Linux guest gets a reply of the same size. I've also increased sysctl -w net.ipv4.tcp_rmem='70000 87380 87380 and tried with sysctl -w net.ipv4.tcp_mtu_probing=1 (and also =0). There is no IPv3 packet fragmentation, all packets have the DF flag set. It works the other way round: the Linux guest can send TCP packets of 6900 bytes of payload and my emulator understands them. This is very strange to me, because only TCP packets seem to be affected (large ICMP packets go through). Any idea what can be imposing this limit? Any idea how to do debug it in the Linux kernel? See the tcpdump -n -vv output below. tcpdump was run on the Linux guest. The last line is interesting: 4060 bytes of TCP payload is sent to the guest, and it doesn't get any reply packet from the Linux guest for half a minute. 14:59:32.000057 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [S], cksum 0x8da0 (correct), seq 10000000, win 14600, length 0 14:59:32.000086 IP (tos 0x10, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 44) 192.168.33.15.22 > 192.168.33.1.36522: Flags [S.], cksum 0xc37f (incorrect -> 0x5999), seq 1415680476, ack 10000001, win 19920, options [mss 9960], length 0 14:59:32.000218 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0xa752 (correct), ack 1, win 14600, length 0 14:59:32.000948 IP (tos 0x10, ttl 64, id 53777, offset 0, flags [DF], proto TCP (6), length 66) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], cksum 0xc395 (incorrect -> 0xfa01), seq 1:27, ack 1, win 19920, length 26 14:59:32.001575 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0xa738 (correct), ack 27, win 14600, length 0 14:59:32.001585 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 65) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], cksum 0x48d6 (correct), seq 1:26, ack 27, win 14600, length 25 14:59:32.001589 IP (tos 0x10, ttl 64, id 53778, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.15.22 > 192.168.33.1.36522: Flags [.], cksum 0xc37b (incorrect -> 0x9257), ack 26, win 19920, length 0 14:59:32.001680 IP (tos 0x10, ttl 64, id 53779, offset 0, flags [DF], proto TCP (6), length 496) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], seq 27:483, ack 26, win 19920, length 456 14:59:32.001784 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0xa557 (correct), ack 483, win 14600, length 0 14:59:32.006367 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 1136) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 26:1122, ack 483, win 14600, length 1096 14:59:32.044150 IP (tos 0x10, ttl 64, id 53780, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.15.22 > 192.168.33.1.36522: Flags [.], cksum 0xc37b (incorrect -> 0x8c47), ack 1122, win 19920, length 0 14:59:32.045310 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 312) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 1122:1394, ack 483, win 14600, length 272 14:59:32.045322 IP (tos 0x10, ttl 64, id 53781, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.15.22 > 192.168.33.1.36522: Flags [.], cksum 0xc37b (incorrect -> 0x8b37), ack 1394, win 19920, length 0 14:59:32.925726 IP (tos 0x10, ttl 64, id 53782, offset 0, flags [DF], proto TCP (6), length 1112) 192.168.33.15.22 > 192.168.33.1.36522: Flags [.], seq 483:1555, ack 1394, win 19920, length 1072 14:59:32.925750 IP (tos 0x10, ttl 64, id 53784, offset 0, flags [DF], proto TCP (6), length 312) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], seq 1555:1827, ack 1394, win 19920, length 272 14:59:32.927131 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x9bcf (correct), ack 1555, win 14600, length 0 14:59:32.927148 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x9abf (correct), ack 1827, win 14600, length 0 14:59:32.932248 IP (tos 0x10, ttl 64, id 53785, offset 0, flags [DF], proto TCP (6), length 56) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], cksum 0xc38b (incorrect -> 0xd247), seq 1827:1843, ack 1394, win 19920, length 16 14:59:32.932366 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x9aaf (correct), ack 1843, win 14600, length 0 14:59:32.964295 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 104) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 1394:1458, ack 1843, win 14600, length 64 14:59:32.964310 IP (tos 0x10, ttl 64, id 53786, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.15.22 > 192.168.33.1.36522: Flags [.], cksum 0xc37b (incorrect -> 0x85a7), ack 1458, win 19920, length 0 14:59:32.964561 IP (tos 0x10, ttl 64, id 53787, offset 0, flags [DF], proto TCP (6), length 88) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], seq 1843:1891, ack 1458, win 19920, length 48 14:59:32.965185 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x9a3f (correct), ack 1891, win 14600, length 0 14:59:32.965196 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 104) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 1458:1522, ack 1891, win 14600, length 64 14:59:32.965233 IP (tos 0x10, ttl 64, id 53788, offset 0, flags [DF], proto TCP (6), length 88) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], seq 1891:1939, ack 1522, win 19920, length 48 14:59:32.965970 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x99cf (correct), ack 1939, win 14600, length 0 14:59:32.965979 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 568) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 1522:2050, ack 1939, win 14600, length 528 14:59:32.966112 IP (tos 0x10, ttl 64, id 53789, offset 0, flags [DF], proto TCP (6), length 520) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], seq 1939:2419, ack 2050, win 19920, length 480 14:59:32.970059 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x95df (correct), ack 2419, win 14600, length 0 14:59:32.970089 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 616) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 2050:2626, ack 2419, win 14600, length 576 14:59:32.981159 IP (tos 0x10, ttl 64, id 53790, offset 0, flags [DF], proto TCP (6), length 72) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], cksum 0xc39b (incorrect -> 0xa84f), seq 2419:2451, ack 2626, win 19920, length 32 14:59:32.982347 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x937f (correct), ack 2451, win 14600, length 0 14:59:32.982357 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 104) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 2626:2690, ack 2451, win 14600, length 64 14:59:32.982401 IP (tos 0x10, ttl 64, id 53791, offset 0, flags [DF], proto TCP (6), length 88) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], seq 2451:2499, ack 2690, win 19920, length 48 14:59:32.982570 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x930f (correct), ack 2499, win 14600, length 0 14:59:32.982702 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 104) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 2690:2754, ack 2499, win 14600, length 64 14:59:33.020066 IP (tos 0x10, ttl 64, id 53792, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.15.22 > 192.168.33.1.36522: Flags [.], cksum 0xc37b (incorrect -> 0x7e07), ack 2754, win 19920, length 0 14:59:33.983503 IP (tos 0x10, ttl 64, id 53793, offset 0, flags [DF], proto TCP (6), length 72) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], cksum 0xc39b (incorrect -> 0x2aa7), seq 2499:2531, ack 2754, win 19920, length 32 14:59:33.983810 IP (tos 0x10, ttl 64, id 53794, offset 0, flags [DF], proto TCP (6), length 88) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], seq 2531:2579, ack 2754, win 19920, length 48 14:59:33.984100 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x92af (correct), ack 2531, win 14600, length 0 14:59:33.984139 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x927f (correct), ack 2579, win 14600, length 0 14:59:34.022914 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 104) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 2754:2818, ack 2579, win 14600, length 64 14:59:34.022939 IP (tos 0x10, ttl 64, id 53795, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.15.22 > 192.168.33.1.36522: Flags [.], cksum 0xc37b (incorrect -> 0x7d77), ack 2818, win 19920, length 0 14:59:34.023554 IP (tos 0x10, ttl 64, id 53796, offset 0, flags [DF], proto TCP (6), length 88) 192.168.33.15.22 > 192.168.33.1.36522: Flags [P.], seq 2579:2627, ack 2818, win 19920, length 48 14:59:34.027571 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40) 192.168.33.1.36522 > 192.168.33.15.22: Flags [.], cksum 0x920f (correct), ack 2627, win 14600, length 0 14:59:34.027603 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 4100) 192.168.33.1.36522 > 192.168.33.15.22: Flags [P.], seq 2818:6878, ack 2627, win 14600, length 4060

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• Joining two routers together, but I have no access to the second router, although I know it's IP address and Gateway

  - by JohnnyVegas

  I have temporarily moved into a rented apartment for 4 months, which has wireless. The trouble I am having is that the access points here are wifi only and no RJ45 and I need to use RJ45 to connect some equipment that I am working with. I have purchased an RT-N66U and installed Tomato (shibby ver. 1.28) and successfully replaced the existing access point, but now I want to enable the access point that I have replaced as it links wirelessly to 3 others. Can I plug in a cable from the access point to my RT-N66U and get it to access the internet via my router? I have no access to the existing wireless access point, and don't want to reset it as it's not mine. There is another router situated in the roof somewhere which I also have no access to, but it's supplying my RT-N66U internet and I most definitely have a double-nat, which although isn't the best way of doing things I am limited with what I can do. Any suggestions on routing tables, vlans etc would be helpful, but I have no experience in these fields before - but I know the tomato firmware can cater for this. My router is set to IP 10.0.1.1 and dhcp is 10.0.1.100-200 The wireless access point address was 192.168.1.2 but this was assigned by the router in the roof which has the address 192.168.1.1. There is a cable from this router going to a wall socket which I now have my RT-N66u attached to via the WAN port. I understand it's scruffy and it isn't the way to do things but I have tried to ask for the admin details but as the wireless network is looked after by a third party and nobody knows their details I am stuck with this dilemma. I could buy three wireless access points and replace the existing but this isn't what I want to do, and although I have installed plenty of DD-WRT wireless repeater bridges they simply don't work here for some unknown reason. The phone line here is very noisy too and I don't have the rights to install ADSL in a building that isn't mine, and 3G coverage isn't good enough either. Thanks for your time

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• New router messed up server 2003 setup...

  - by Aceth

  Hey, We were sent a new 2wire router today configured it as best we can to match the old bt voyager. We've also got X static IP's. We've manage to get our webserver on one of the new IP's public facing. then we use a hardware firewall which is in a DMZ again with a different static IP. This firewall then is our gateway for our internal LAN. with a few servers etc. The problem we're having is only our PDC (primary Domain controller which has exchange 2003 on) can't ping externally even an external IP. We've connected laptops to the 2wire router and obtain a private ip 192.168.1.X and it works fine can ping etc. our other servers with an internal ip behind the firewall can ping out fine. We've connected to the firewalls logging console and the pings from the server are allowed through so its fine there. The server in question is a Windows server 2003 R2 Enterprise SP2 + Exchange 2003 Server doesn't have firewall turned on. it has static private IP .. gateway is pointing to the right one External Static IP is routing fine inwards We've ran out of ideas .. help??

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• pfSense router on a LAN with two gateways

  - by JohnCC

  I have a LAN with an ADSL modem/router on it. We have just gained an alternative high-speed internet connection at our location, and I want to connect the LAN to it, eventually dropping the ADSL. I've chosen to use a small PFSense box to connect the LAN to the new WAN connection. Two servers on the LAN run services accessible to the outside via NAT using the single ADSL WAN IP. We have DNS records which point to this IP. I want to do the same via the new connection, using the WAN IP there. That connection permits multiple IPs, so I have configured pfSense using virtual IP's, 1:1 NAT and appropriate firewall rules. When I change the servers' default gateway settings to the pfSense box, I can access the services via the new WAN IPs without a problem. However, I can no longer access them via the old WAN IP. If I set the servers' default gateway back to the ADSL router, then the opposite is true - I can access the services via the ADSL IP, but not via the new one. In the first case, I believe this is because an incoming SYN packet arrives at the ADSL WAN IP, and is NAT'd and sent to the internal IP of the server. The server responds with a SYN/ACK which it sends via its default gateway, the pfSense box. The pfSense box sees a SYN/ACK that it saw no SYN for and drops the packet. Is there any sensible way around this? I would like the services to be accessible via both IPs for a short period at least, since once I change the DNS it will take a while before everyone picks up the new address.

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• Route all wlan0 traffic over tun0

  - by Tuinslak

  I'm looking for a way to route all wlan0 traffic (tcp and udp) over tun0 (openvpn). However, all other traffic originating from the device itself should not be routed through tun0. I'm guessing this could be realized using iptables or route, but none of my options seem to work. # route add -net 0.0.0.0 gw 172.27.0.1 dev wlan0 SIOCADDRT: No such process Info: This is because the VPN server is not redundant, and wlan users are not really important. However, all services running on the device are fairly important and having a VPN virtual machine with no SLA on it is just a bad idea. Trying to minimize the odds of something going wrong. So setting the VPN server as default gateway is not really an option. I also want all wlan0 user to use the VPN server's IP address as external IP. Edit with the script provided: root@ft-genesi-xxx ~ # route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 172.27.0.17 0.0.0.0 255.255.255.255 UH 0 0 0 tun0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.13.37.0 0.0.0.0 255.255.255.0 U 0 0 0 wlan0 172.27.0.0 172.27.0.17 255.255.192.0 UG 0 0 0 tun0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0 root@ft-genesi-xxx ~ # ./test.sh RTNETLINK answers: No such process root@ft-genesi-xxx ~ # cat test.sh #!/bin/sh IP=/sbin/ip # replace with the range of your wlan network, or use fwmark instead ${IP} rule add from 10.13.37.0/24 table from-wlan ${IP} route add default dev tun0 via 127.72.0.1 table from-wlan ${IP} route add 10.13.37.0/24 dev wlan0 table from-wlan

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• How to lookup an IP address in an Excel spreadsheet?

  - by Kevin Williams

  I am working with a decent sized spreadsheet of domains and server names. Another user of the spreadsheet needs the IP address for each of the DNS entries on the worksheet. Instead of manually adding and then having to maintain this list I was hoping there was an easy way to do an IPAddress lookup to display the IP address in a cell. I've seen some VBScripts that call gethostbyname, e.g.: Declare Function GetHostByName Lib "wsock32.dll" Alias "gethostbyname" (ByVal Host As String) As Long But I'm not a VB expert so I'm not sure if this is the right way to go. Any advice/links would be appreciated! also if this is a question better suited for Stack Overflow - let me know, I'm new here.

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• Using IP Restrictions with URL Rewrite-Week 25

  - by OWScott

  URL Rewrite offers tremendous flexibility for customizing rules to your environment. One area of functionality that is often desired for URL Rewrite is to allow a large list of approved or denied IP addresses and subnet ranges. IIS’s original IP Restrictions is helpful for fully blocking an IP address, but it doesn’t offer the flexibility that URL Rewrite does. An example where URL Rewrite is helpful is where you want to allow only authorized IPs to access staging.yoursite.com, but where staging.yoursite.com is part of the same site as www.yoursite.com. This requires conditional logic for the user’s IP. This lesson covers this unique situation while also introducing Rewrite Maps, server variables, and pairing rules to add more flexibility. This is week 25 of a 52 week series for the Web Pro. Past and future videos can be found here: http://dotnetslackers.com/projects/LearnIIS7/ You can find this week’s video here.

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• google.com different IP in different countries. How?

  - by HeavyWave

  If you ping google.com from different countries you will get replies from local google servers. How does that work? Can a DNS record have multiple A addresses? Could someone point me to the technology they use to do that? Update. OK, so Google's DNS server gives out a different IP based on the location. But, as Alexandre Jasmin pointed out, how do they track the location? Surely their DNS won't ever see your IP address. Is the server querying Google's DNS guaranteed to be from the location it represents?

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• Are there any negative impact running all services on a single static IP?

  - by Jake

  I need to setup a VPN trunk (with remote branch office location), Video Conference and Web Server on-premise in the office. I am used to ISP providing blocks of 8 or 16 IPs. But I have a new ISP which says they only can provide a single IP. Are there any issues with running all services on a single IP? I don't think this has any thing to do with bandwidth..? I'm not using SSL certificates... I can do port forwarding to different machines... What else...? Disclaimer: I am a programmer by training. Sorry for noob question.

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• Two different sites, same IP, same top-level domain, on IIS 7.5 -- one works and the other displays HTTP 404 error

  - by user717236

  I'm running a Windows 2008 R2 box with IIS 7.5 as the web server. On IIS, I have two websites: mysubsite1.mysite.com and mysubsite2.mysite.com. There is only one IP on the server and both sites share this IP. Here is how I have the bindings configured: mysubsite1.mysite.com works fine. However, mysubsite2.mysite.com gives me the following error: Not Found HTTP Error 404. The requested resource is not found. Now, if I change the Host name field for mysubsite1.mysite.com to blank and restart the web server, both sites work! The question is why is the host name field for the first site causing an HTTP 404 error for the second site when both sites' Host name fields are filled? I would appreciate any insight. Thank you.

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• Is your IP address neighborhood important for SEO?

  - by Evgeny

  Can other websites on your shared host affect the rank of your website in the Google index? (same IP address as yours, potentially malicious/low-trust content) Can other websites on your IP class affect the rank of your website in the Google index? (different actual IP, malicious/low-trust content) Clarification: Domain class, is what you get when you run a whois query on an IP address. Example: NetRange: 69.163.128.0 - 69.163.255.255 CIDR: 69.163.128.0/17 PS: Prefer answers with experience or links to trustworthy material, over speculations, assumptions and gut feelings.

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• how to get IP adress of google search/crawler bot to add to our white list of ip address

  - by Jayapal Chandran

  Hi, Google webmaster tools says network unreachable. When i contacted my hosting provider they said that they have installed firewall which could block frequent incoming ip addresses and they dont know the google's ip adress to unblock. so they requested me to find google search/crawler bot's ip adress so that they can add it to their whitelist. How to find the ip address of google search bot or crawler bot? My site stopped appearing in google search. My hits had gone too low. What should i do? any kind of reply would he helpful.

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• How to get two seperate remote domain controllers with same IP to work?

  - by Mr. Mister

  Hi, I have a VPN setup between multiple locations. Between each location and the central point (me), is a trust between our domain controllers. It all works great.. A new location wants to join, but their AD controller is using an IP address that is already in use by another AD in a separate location. Neither locations can change their IP addresses, but apparently there is a NAT rule that could be used to allow communication between each AD controller? The central site has a Cisco 5510 firewall which could perform the NAT, but I am unsure of the logic behind the NAT rule. Is anyone able to explain or help out? Thanks.

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• How to get all rapidshare and their sub domain ip-address?

  - by tacoen

  How to get all rapidshare and their sub domain ip-address?

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• Changing internal home network ip address for connected devices

  - by oshirowanen

  I have a few computers at home. For each of the computers, I can see the internal home network ip address on any given device by typing in ifconfig in the terminal. If the device is connected to the home network via ethernet connection or via the built-in wireless connections in laptops, the internal ip address for each of the devices seems to be 192.168.0.X. However, when I connect one of the devices using an external usb modem wireless adapter, which connects to the home network through wireless, when I check the ip address via ifconfig, for some reason it gets assigned 192.168.42.X instead. Why are the ethernet and build in wireless connections getting 192.168.0.X, but the external usb wireless adapter gets 192.168.42.X? Most importantly, is it possible to force it to get an internal ip address of 192.168.0.X?

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• How do you have one IP address and many websites?

  - by johnny

  Hi, How can I have it where I have one IP address that sits on the Internet but many web names? For example, when a hosting company has a shared IP but I get unlimited domain names (along with everyone else on that box). I have a box on the Internet but I want to point to another machine that holds a different website when someone types in the different www...(it's sitting right next to it in just a different box). Is that all subdomaining? Thank you. EDIT: I am the hosting company.

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• WIth more mobile users, my geo ip database is becoming useless.

  - by Marius

  Hello there, I've been enjoying the benefits of Geo IP lookup from database for some time. Its great. People are increasingly trying to access my site from a mobile phones or 3G modems, and their physical location seems to have little relation to whereabouts my IP lookup tells me they are. A user who is on the east cost of my country, may be looked up as being in the far inland, or up north. And one user may be reported as being in one location in one moment, and seconds later, be 100s of kilometers away. This is becoming a problem, and I need to find a solution. I am already updating my database monthly, but it has little effect. What can be done? Thank you for your time. Kind regardsMarius

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• Fixing IP Renewal After Laptop Suspend

  - by Cerin

  I have a laptop running Ubuntu 10.04, and I've noticed that with some wifi networks, but not all, I'm unable to reconnect after coming out of suspension. I've tried both Network Manager and Wicd management daemons, and both get through validation, but get hung up on "Acquiring IP address...". The only solution I've found is to reboot the machine, after which it acquires an IP address very quickly. What's the underlying issue here? What would be a more efficient way to resolve the problem? EDIT: I've noticed that if I open Wicd and manually press "Connect", it fails to acquire an IP. However, if I do nothing and let it automatically try and connect, it acquires an IP and connects just fine...

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• How to change the IP address on my Ubuntu virtual NIC

  - by DextrousDave

  I have a physical windows system, on which I run Vmware Workstation. Now on VMware I run Ubuntu 12.10. I am running a webserver on Ubuntu via LAMP, inside VMware. Problem: Now my local IP address for my virtual NIC (the one Ubuntu is using) has an address of 192.168.159.7, and my home router only issues IP addresses of the range 10.0.0.x. So if I want to port forward to the virtual NIC, which has a 192.168 address, I cannot, so my LAMP webserver cannot be accessed externally since the router does not know to send the packets on port 80 to the virtual NIC... How do I fix that? The only way I guess is to assign a 10.0.0.x ip address to the virtual NIC?? But how do I do that? I tried to do it on the host Windows machine with 'Get my IP address automatically' but it issues a 192.168 address every time... Thank you

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