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• UFW: force traffic thru OpenVPN tunnel / do not leak any traffic

  - by hotzen

  I have VPN access using OpenVPN and try to create a safe machine that does not leak traffic over non-VPN interfaces. Using the firewall UFW I try to achieve the following: Allow Access from LAN to the machine's web-interface Otherwise only allow Traffic on tun0 (OpenVPN-Tunnel interface when established) Reject (or forward?) any traffic over other interfaces Currently I am using the following rules (sudo ufw status): To Action From -- ------ ---- 192.168.42.11 9999/tcp ALLOW Anywhere # allow web-interface Anywhere on tun0 ALLOW Anywhere # out only thru tun0 Anywhere ALLOW OUT Anywhere on tun0 # in only thru tun0 My problem is that the machine is initially not able to establish the OpenVPN-connection since only tun0 is allowed, which is not yet established (chicken-egg-problem) How do I allow creating the OpenVPN connection and from this point onward force every single packet to go thru the VPN-tunnel?

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• Collision Detection for a 2D RPG

  - by PHMitrious

  First of all, I have done some research on this topic before asking, and I'm asking this question as a mean to get some opinions on this topic, so I don't make a decision only on my own, but taking into account other people's experience as well. I'm starting a 2D online RPG project. I am using SFML for graphics and input and I'm creating a basic game structure and all for the game, creating modules for each part of the game. Well, let me get to the point I just wanted to give you guys some context. I want to decide on how I'm going to work with collision detection. Well I'm kinda going to work on maps with a tile map divided in layers (as usual) and add an extra 2 layers - not exactly in the map - for objects. So I'll have collisions between objects and agents (players - npcs - monsters - spells etc) and agents and tiles. The seconds one can be easily solved the first one need a little bit of work. I considered both creating a basic collision test engine using polygons and a quadtree to diminish tests since I'm going to be working with big maps with lots of objects - creating both a physical and graphical world representation. And I also considered using a physics engine like Box2D for collision tests. I think the first approach would take more work on my part but the second one would have the overhead of using a whole physics engine for just collision detection and no physics. What do you guys think ?

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• Transform coordinates from 3d to 2d without matrix or built in methods

  - by Thomas

  Not to long ago i started to create a small 3D engine in javascript to combine this with an html5 canvas. One of the issues I run into is how can you transform 3d to 2d coords. Since I cannot use matrices or built in transformation methods I need another way. I've tried implementing the next explanation + pseudo code: http://freespace.virgin.net/hugo.elias/routines/3d_to_2d.htm Unfortunately no luck there. I've replace all the input variables with data from my own camera and object classes. I have the following data: An object with a rotation, position vector and an array of 4 3d coords (its just a plane) a camera with a position and rotation vector the viewport - a square 600 x 600 surface. The example uses a zoom factor which I've set as 1 Most hits on google use either matrix calculations or don't implement camera rotation. Basic transformation should be like this: screen.x = x / z * zoom screen.y = y / z * zoom Can anyone point me in the right direction or explain to me howto achieve this? edit: Thanks for all your posts, I haven't been able to apply all this to my project yet but I hope to do this soon.

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• What's a good entity hierarchy for a 2D game?

  - by futlib

  I'm in the process of building a new 2D game out of some code I wrote a while ago. The object hierarchy for entities is like this: Scene (e.g. MainMenu): Contains multiple entities and delegates update()/draw() to each Entity: Base class for all things in a scene (e.g. MenuItem or Alien) Sprite: Base class for all entities that just draw a texture, i.e. don't have their own drawing logic Does it make sense to split up entities and sprites up like that? I think in a 2D game, the terms entity and sprite are somewhat synonymous, right? But I do believe that I need some base class for entities that just draw a texture, as opposed to drawing themselves, to avoid duplication. Most entities are like that. One weird case is my Text class: It derives from Sprite, which accepts either the path of an image or an already loaded texture in its constructor. Text loads a texture in its constructor and passes that to Sprite. Can you outline a design that makes more sense? Or point me to a good object-oriented reference code base for a 2D game? I could only find 3D engine code bases of decent code quality, e.g. Doom 3 and HPL1Engine.

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• OOP oriented PHP app source code samples and advice

  - by abel

  The day I have been dreading has arrived. I never felt OOP or good software design was important(I knew they were important, but I thought I could manage without them.). However having read otherwise almost everywhere on the interwebs, I started dreading the day when my client would ask me for new features in an existing app. The day has come and the pain is unbearable! I have never coded my PHP websites "properly"(PHP is my primary language and the bulk of my work. I am learning Python (using web2py)) I take care that the website doesn't fall apart in a daily use scenario. I code pages like I was creating a list of static html files with bits of "magic code" in each of them(this bugs me a lot). How do I make the whole app more or less a single object? For eg. How do I design the object model for an invoicing app? I use a lot of functions for doing any particular thing in the same fashion throughout the app(for eg. validation, generating ids, calculating taxes etc.). I know the basics of OOP in general. Can anyone point me to source code samples of functional apps written in php? Or can someone provide pointers so I can recode my existing apps in a more modular way.

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• Using symbolic links with git

  - by Alfredo Palhares

  I used to have my system configuration files all in one directory for better management but now i need to use some version control on it. But the problem is that git doesn't understand symbolic links that point to outside of the repository, and i can't invert the role ( having the real files on the repository and the symbolic links on their proper path ) since some files are read before the kernel loads. I think that I can use unison to sync the files in the repo and and the their paths, but it's just not practical. And hard links will probably be broken. Any idea ?

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• Were the first assemblers written in machine code?

  - by The111

  I am reading the book The Elements of Computing Systems: Building a Modern Computer from First Principles, which contains projects encompassing the build of a computer from boolean gates all the way to high level applications (in that order). The current project I'm working on is writing an assembler using a high level language of my choice, to translate from Hack assembly code to Hack machine code (Hack is the name of the hardware platform built in the previous chapters). Although the hardware has all been built in a simulator, I have tried to pretend that I am really constructing each level using only the tools available to me at that point in the real process. That said, it got me thinking. Using a high level language to write my assembler is certainly convenient, but for the very first assembler ever written (i.e. in history), wouldn't it need to be written in machine code, since that's all that existed at the time? And a correlated question... how about today? If a brand new CPU architecture comes out, with a brand new instruction set, and a brand new assembly syntax, how would the assembler be constructed? I'm assuming you could still use an existing high level language to generate binaries for the assembler program, since if you know the syntax of both the assembly and machine languages for your new platform, then the task of writing the assembler is really just a text analysis task and is not inherently related to that platform (i.e. needing to be written in that platform's machine language)... which is the very reason I am able to "cheat" while writing my Hack assembler in 2012, and use some preexisting high level language to help me out.

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• Linux software RAID 10 implementation

  - by fabrik

  Hello there! I don't want to force anybody to make it on behalf of me but trust me: i've looked hundreds of sites and i can't find a good starting point for this. I have 4x500Gb HDD's which i want to set up in RAID 10. The most promising description is here, but it's a little old and unclear for me, above all i prefer Debian over Ubuntu (i know there are slight or no differences). Is it possible to build RAID 10 with Debian's installer or i need to build RAID 1 first in the installer then use mdadm later? What is the best practice for building software RAID 10 under Linux (Debian)? Thanks for your time, fabrik

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• Importing Delicious export into Firefox 3

  - by Jordan Reiter

  The HTML export file from Delicious creates an HTML file that, while importable into Firefox, loses all of the tags, which pretty much misses the point of delicious. Every link I've found to do the import doesn't work: The online converter Delicious-to-Firefox 3 keeps throwing a server error; the "better" version is down I tried using the trick of syncing Delicious bookmarks to Flock and then restoring that file to my Firefox browser. Although the bookmarks are in Firefox, they don't show up anywhere. I know they're in Firefox because when I create a backup file, they're in the JSON file but they refuse to show in the browser anywhere (clicking on any tag shows an empty list) Basically, I'm looking for someone who has successfully imported their delicious bookmarks, with tags, into Firefox 3.6.13 (Mac).

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• C# vector class - Interpolation design decision

  - by Benjamin

  Currently I'm working on a vector class in C# and now I'm coming to the point, where I've to figure out, how i want to implement the functions for interpolation between two vectors. At first I came up with implementing the functions directly into the vector class... public class Vector3D { public static Vector3D LinearInterpolate(Vector3D vector1, Vector3D vector2, double factor) { ... } public Vector3D LinearInterpolate(Vector3D other, double factor { ... } } (I always offer both: a static method with two vectors as parameters and one non-static, with only one vector as parameter) ...but then I got the idea to use extension methods (defined in a seperate class called "Interpolation" for example), since interpolation isn't really a thing only available for vectors. So this could be another solution: public class Vector3D { ... } public static class Interpolation { public static Vector3D LinearInterpolate(this Vector3D vector, Vector3D other, double factor) { ... } } So here an example how you'd use the different possibilities: { var vec1 = new Vector3D(5, 3, 1); var vec2 = new Vector3D(4, 2, 0); Vector3D vec3; vec3 = vec1.LinearInterpolate(vec2, 0.5); //1 vec3 = Vector3D.LinearInterpolate(vec1, vec2, 0.5); //2 //or with extension-methods vec3 = vec1.LinearInterpolate(vec2, 0.5); //3 (same as 1) vec3 = Interpolation.LinearInterpolation(vec1, vec2, 0.5); //4 } So I really don't know which design is better. Also I don't know if there's an ultimate rule for things like this or if it's just about what someone personally prefers. But I really would like to hear your opinions, what's better (and if possible why ).

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• How do you name/brand software?

  - by JasCav

  I am working on an application that is brand new. We have been using an internal name up to this point, but it's not very imaginative and is definitely not good from a branding standpoint. I have been tasked to come up with a name for the software. I am really struggling with this as every name I have thought about really doesn't seem to do the software justice. I have tried acronyms, mythology names, scientific names, etc. I may be being a bit picky, but I feel like the name should just hit me when its right. Here are my requirements: The name has to be easy to say (and hopefully catchy). The name has to relate back to what the software does. The name has to be able to be branded. (For example, vivid imagery, tagline, etc.) So, although I can't give the specifics of the software, I was hoping the brains here could provide some insight as to how I should go about naming/branding a piece of software?

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• Canon MG6100 series USB printer receives job but doesn't physically print

  - by Old-linux-fan

  Printer MP6150 driver installed itself upon plugging in the printer. Printer is recognized (lsusb shows it) but does not mount. If the printer is recognized, the driver must be working (or?), but something is blocking the system from mounting the printer. Tried the usual things: power of printer, restart Ubuntu etc. Listed below result of lsusb and fstab: hans@kontor-linux:~$ lsusb Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 004: ID 04a9:174a Canon, Inc. Bus 002 Device 002: ID 1058:1001 Western Digital Technologies, Inc. External Hard Disk [Elements] Bus 004 Device 002: ID 046d:c517 Logitech, Inc. LX710 Cordless Desktop Laser hans@kontor-linux:~$ sudo cat /etc/fstab [sudo] password for hans: # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/sda6 during installation UUID=eaf3b38d-1c81-4de9-98d4-3834d674ff6e / ext4 errors=remount-ro 0 1 # swap was on /dev/sda5 during installation UUID=93a667d3-6132-45b5-ad51-1f8a46c5b437 none swap sw 0 0

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• Is `break` and `continue` bad programming practice?

  - by Mikhail

  My boss keeps mentioning nonchalantly that bad programmers use break and continue in loops. I use them all the time because they make sense; let me show you the inspiration: function verify(object) { if (object->value < 0) return false; if (object->value > object->max_value) return false; if (object->name == "") return false; ... } The point here is that first the function checks that the conditions are correct, then executes the actual functionality. IMO same applies with loops: while (primary_condition) { if (loop_count > 1000) break; if (time_exect > 3600) break; if (this->data == "undefined") continue; if (this->skip == true) continue; ... } I think this makes it easier to read & debug; but I also don't see a downside. Please comment.

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• Routing different domains on a VPS

  - by Hans Wassink

  We just went from shared hosting to a VPS server. We have several domain names that we have pointing to our dns, but they all point to the root of the server. What I would like now is a setup where every domain name gets its own map so we can run different sites on the VPS server. Like: www.example.com points to: /var/www/example.com www.imapwnu.com points to: /var/www/imapwnu.com First of all, is this possible? Second, I have root SSH access and Webmin, on a LAMP server running on Ubuntu. Webmin doesnt have Bind9 (I dont know if I need that, some forums pointed me towards something called bind). Thanks in advance

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• Wireless DHCP doesn't work until wired Ethernet plugged in

  - by MT_Head

  A client of mine has an Asus R1F tablet running Windows XP Tablet SP3. It has an Intel 3945ABG wireless card; wired Ethernet is a Realtek something-or-other. In the past few days, it's developed an odd problem: WiFi authenticates, but can't get an address via DHCP. plug in wired Ethernet - both interfaces get good addresses unplug cable, WiFi continues to work until shutdown. Next morning, repeat process. I've tried: turning WiFi off/on (there's a slider switch) disabling/re-enabling via Device Mangler uninstalling and reinstalling the driver for the 3945ABG... changing from Intel Pro/SET to Windows Wireless Zero Config (and back) restarting the router changing the static DHCP assignments at the router upgrading the router firmware, just on general principles The router/access point is pfSense 1.2.3RC1 (was 1.2.2); wireless card is Atheros-based. None of the 12 other users (5 with tablets) are having problems.

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• When not to use Spring to instantiate a bean?

  - by Rishabh

  I am trying to understand what would be the correct usage of Spring. Not syntactically, but in term of its purpose. If one is using Spring, then should Spring code replace all bean instantiation code? When to use or when not to use Spring, to instantiate a bean? May be the following code sample will help in you understanding my dilemma: List<ClassA> caList = new ArrayList<ClassA>(); for (String name : nameList) { ClassA ca = new ClassA(); ca.setName(name); caList.add(ca); } If I configure Spring it becomes something like: List<ClassA> caList = new ArrayList<ClassA>(); for (String name : nameList) { ClassA ca = (ClassA)SomeContext.getBean(BeanLookupConstants.CLASS_A); ca.setName(name); caList.add(ca); } I personally think using Spring here is an unnecessary overhead, because The code the simpler to read/understand. It isn't really a good place for Dependency Injection as I am not expecting that there will be multiple/varied implementation of ClassA, that I would like freedom to replace using Spring configuration at a later point in time. Am I thinking correct? If not, where am I going wrong?

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• What could be causing frequent display freezes?

  - by austen

  I just installed Ubuntu 14.04 two days ago (coming from Win8) and in the two days that I've been using it, my display has frozen four or five times. The mouse won't move but the keyboard does respond so I can use the Ctrl+Alt+Bkspc command to fix it. It seems like it might just be the display freezing because one of the times I was watching a Youtube video and the audio continued playing. I have an Nvidia graphics card with the most recent Nvidia drivers for it enabled. I see that a lot of questions about Ubuntu freezing get marked as a duplicate and pretty much always linked back to a thread about what to do when it freezes. Clearly, I've got that bit figured out already and I did read that thread for further advice. What I'm looking for though is how to fix this permanently. output from lspci -nnk | grep -iA2 VGA: 00:02.0 VGA compatible controller [0300]: Intel Corporation 3rd Gen Core processor Graphics Controller [8086:0166] (rev 09) Subsystem: Lenovo Device [17aa:2200] Kernel driver in use: i915 Update: JohnnyEnglish pointed out that Ubuntu is using the integrated graphics, not my Nvidia card. It turns out my laptop uses Nvidia Optimus and I cannot enable only the graphics card through the BIOS. I found out about Nvidia Prime and got it set up using this article. The settings panel which allows you to select the graphics says that 'performance mode' is enabled but when I check which graphics controller is enabled through the terminal, it still says it's using the integrated graphics. I'm not sure if this could be causing the freezes but I guess it's a starting point. Any ideas on how to resolve this?

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• SharePoint 2010 Video Training

  - by Sahil Malik

  Ad:: SharePoint 2007 Training in .NET 3.5 technologies (more information). Yes, the DVD is finally available. This is an exhaustive 14 hour video course that Carl and I recorded back in April. It is an end-to-end overview of SharePoint 2010. You can view more details including ordering information about the DVD here. And if you’re interested, a SharePoint 2007 video training version is also available. Carl and I worked quite hard on putting these together, so we hope you enjoy these. Detailed Table of Contents: Introduction (13:49) 30,000 Foot Overview (42:07) Application Management (43:35) User Experience (16:00) Writing Code Part 1 (1:07:49) Writing Code Part 2 (34:41) Simple Web Parts (14:01) Visual Web Parts (6:35) Pages (35:02) Putting it All Together (29:13) Client Side Technology (49:19) ADO.NET Data Services (51:29) Custom Data Services (43:30) Managing Data (29:02) Managing Data: Content Types (17:11) Managing Data: Events (19:22) Managing Data: List Scalability (35:51) Managing Data: Querying (20:07) Enterprise Content Management: DocumentIDs and Document Sets (16:44) Enterprise Content Management: Metadata Infrastructure (22:13) Enterprise Content Management: Record Management (26:27) Enterprise Content Management: Content Organizer (7:21) Enterprise Content Management: Enterprise Content Types (11:21) Business Connectivity Services (BCS) in the SharePoint Designer (26:09) BCS in Visual Studio (9:57) Workflows in the SharePoint Designer (22:07) Workflows in Visual Studio (19:01) Business Intelligence (21:14) Excel (15:25) Performance Point (24:37) Security: Claims-Based Authentication (27:13) Security: Secure Store Service (11:04) Security: The SharePoint Object Model (11:16) Comment on the article ....

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• Working with Timelines with LINQ to Twitter

  - by Joe Mayo

  When first working with the Twitter API, I thought that using SinceID would be an effective way to page through timelines. In practice it doesn’t work well for various reasons. To explain why, Twitter published an excellent document that is a must-read for anyone working with timelines: Twitter Documentation: Working with Timelines This post shows how to implement the recommended strategies in that document by using LINQ to Twitter. You should read the document in it’s entirety before moving on because my explanation will start at the bottom and work back up to the top in relation to the Twitter document. What follows is an explanation of SinceID, MaxID, and how they come together to help you efficiently work with Twitter timelines. The Role of SinceID Specifying SinceID says to Twitter, “Don’t return tweets earlier than this”. What you want to do is store this value after every timeline query set so that it can be reused on the next set of queries.  The next section will explain what I mean by query set, but a quick explanation is that it’s a loop that gets all new tweets. The SinceID is a backstop to avoid retrieving tweets that you already have. Here’s some initialization code that includes a variable named sinceID that will be used to populate the SinceID property in subsequent queries: // last tweet processed on previous query set ulong sinceID = 210024053698867204; ulong maxID; const int Count = 10; var statusList = new List<status>(); Here, I’ve hard-coded the sinceID variable, but this is where you would initialize sinceID from whatever storage you choose (i.e. a database). The first time you ever run this code, you won’t have a value from a previous query set. Initially setting it to 0 might sound like a good idea, but what if you’re querying a timeline with lots of tweets? Because of the number of tweets and rate limits, your query set might take a very long time to run. A caveat might be that Twitter won’t return an entire timeline back to Tweet #0, but rather only go back a certain period of time, the limits of which are documented for individual Twitter timeline API resources. So, to initialize SinceID at too low of a number can result in a lot of initial tweets, yet there is a limit to how far you can go back. What you’re trying to accomplish in your application should guide you in how to initially set SinceID. I have more to say about SinceID later in this post. The other variables initialized above include the declaration for MaxID, Count, and statusList. The statusList variable is a holder for all the timeline tweets collected during this query set. You can set Count to any value you want as the largest number of tweets to retrieve, as defined by individual Twitter timeline API resources. To effectively page results, you’ll use the maxID variable to set the MaxID property in queries, which I’ll discuss next. Initializing MaxID On your first query of a query set, MaxID will be whatever the most recent tweet is that you get back. Further, you don’t know what MaxID is until after the initial query. The technique used in this post is to do an initial query and then use the results to figure out what the next MaxID will be.  Here’s the code for the initial query: var userStatusResponse = (from tweet in twitterCtx.Status where tweet.Type == StatusType.User && tweet.ScreenName == "JoeMayo" && tweet.SinceID == sinceID && tweet.Count == Count select tweet) .ToList(); statusList.AddRange(userStatusResponse); // first tweet processed on current query maxID = userStatusResponse.Min( status => ulong.Parse(status.StatusID)) - 1; The query above sets both SinceID and Count properties. As explained earlier, Count is the largest number of tweets to return, but the number can be less. A couple reasons why the number of tweets that are returned could be less than Count include the fact that the user, specified by ScreenName, might not have tweeted Count times yet or might not have tweeted at least Count times within the maximum number of tweets that can be returned by the Twitter timeline API resource. Another reason could be because there aren’t Count tweets between now and the tweet ID specified by sinceID. Setting SinceID constrains the results to only those tweets that occurred after the specified Tweet ID, assigned via the sinceID variable in the query above. The statusList is an accumulator of all tweets receive during this query set. To simplify the code, I left out some logic to check whether there were no tweets returned. If  the query above doesn’t return any tweets, you’ll receive an exception when trying to perform operations on an empty list. Yeah, I cheated again. Besides querying initial tweets, what’s important about this code is the final line that sets maxID. It retrieves the lowest numbered status ID in the results. Since the lowest numbered status ID is for a tweet we already have, the code decrements the result by one to keep from asking for that tweet again. Remember, SinceID is not inclusive, but MaxID is. The maxID variable is now set to the highest possible tweet ID that can be returned in the next query. The next section explains how to use MaxID to help get the remaining tweets in the query set. Retrieving Remaining Tweets Earlier in this post, I defined a term that I called a query set. Essentially, this is a group of requests to Twitter that you perform to get all new tweets. A single query might not be enough to get all new tweets, so you’ll have to start at the top of the list that Twitter returns and keep making requests until you have all new tweets. The previous section showed the first query of the query set. The code below is a loop that completes the query set: do { // now add sinceID and maxID userStatusResponse = (from tweet in twitterCtx.Status where tweet.Type == StatusType.User && tweet.ScreenName == "JoeMayo" && tweet.Count == Count && tweet.SinceID == sinceID && tweet.MaxID == maxID select tweet) .ToList(); if (userStatusResponse.Count > 0) { // first tweet processed on current query maxID = userStatusResponse.Min( status => ulong.Parse(status.StatusID)) - 1; statusList.AddRange(userStatusResponse); } } while (userStatusResponse.Count != 0 && statusList.Count < 30); Here we have another query, but this time it includes the MaxID property. The SinceID property prevents reading tweets that we’ve already read and Count specifies the largest number of tweets to return. Earlier, I mentioned how it was important to check how many tweets were returned because failing to do so will result in an exception when subsequent code runs on an empty list. The code above protects against this problem by only working with the results if Twitter actually returns tweets. Reasons why there wouldn’t be results include: if the first query got all the new tweets there wouldn’t be more to get and there might not have been any new tweets between the SinceID and MaxID settings of the most recent query. The code for loading the returned tweets into statusList and getting the maxID are the same as previously explained. The important point here is that MaxID is being reset, not SinceID. As explained in the Twitter documentation, paging occurs from the newest tweets to oldest, so setting MaxID lets us move from the most recent tweets down to the oldest as specified by SinceID. The two loop conditions cause the loop to continue as long as tweets are being read or a max number of tweets have been read.  Logically, you want to stop reading when you’ve read all the tweets and that’s indicated by the fact that the most recent query did not return results. I put the check to stop after 30 tweets are reached to keep the demo from running too long – in the console the response scrolls past available buffer and I wanted you to be able to see the complete output. Yet, there’s another point to be made about constraining the number of items you return at one time. The Twitter API has rate limits and making too many queries per minute will result in an error from twitter that LINQ to Twitter raises as an exception. To use the API properly, you’ll have to ensure you don’t exceed this threshold. Looking at the statusList.Count as done above is rather primitive, but you can implement your own logic to properly manage your rate limit. Yeah, I cheated again. Summary Now you know how to use LINQ to Twitter to work with Twitter timelines. After reading this post, you have a better idea of the role of SinceID - the oldest tweet already received. You also know that MaxID is the largest tweet ID to retrieve in a query. Together, these settings allow you to page through results via one or more queries. You also understand what factors affect the number of tweets returned and considerations for potential error handling logic. The full example of the code for this post is included in the downloadable source code for LINQ to Twitter.   @JoeMayo

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• Bad disks in ancient server

  - by Joel Coel

  I have a 1998-era Netware 3.12 server that runs everything on our campus: general ledger, purchasing, payroll, student information, grades, you name it. The server has an Adaptec RAID controller with two volumes: RAID 1, 2 17GB scsi disks, Seagate ST318417W RAID 5, 3 4GB scsi disks, 2 Seagate ST34573W and 1 ST34572W. We are currently in the early stages of a project to replace this system, but you don't just jump into a new system like that and so I need to keep this server running until at least November 2011. This week we had not one but two hard drives fail. Thankfully they are from different volumes and we're able to keep running for the moment, but given the close nature of these failures I have serious doubts that I'll be able to avoid catastrophic failure from this server through the November target as is without restoring the RAID redundancy — it'll only take one more drive failure anywhere and I'm completely hosed. We are fortunate enough to have exact match "spares" lying around for both drives, but the spares are in unknown condition. I tried swapping just them in, but the RAID controller isn't smart enough to handle this and it renders the system unbootable. As for the RAID controller itself, there is utility I can get into during POST via a Ctrl-A shortcut, but I can't do much useful from there. To actually manage volumes I must first boot in to Netware, at which point I can use CI/O Array Management Software Version 2.0 to actually look at volume information. I suspect that the normal way to manage things is to boot from a special floppy with the controller software on it, but that floppy is long gone. Going through the options in the RAID software, I think the only supported way to replace a disk in an existing RAID volume is to physically add the disk, boot up and configure it as a "spare" for a volume, force the volume to use the spare to replace an existing down disk (and at this point I'm only guessing) so that the down disk becomes the spare, repair the volume, remove the spare from the volume, and then shut down and remove the disk. Then start all over for the other failed disk. All this amounts to a lot of downtime, assuming I can even make it work and that my spares are any good. As for finding reliable spares, I have no clue where to even begin looking to find a new 4GB scsi drive, or even which exact scsi system I'm looking for, as it's gone through a few different iterations over time. Another option is to migrate this to a virtual machine (hyper-v), but all previous attempts we've made in this area have failed to get very far. When this machine was installed I was just graduating from high school, and so it requires lower level knowledge of netware and dos than I ever developed, or if I did have since forgotten (I'm not exactly a dos neophyte, either). Part of my problem is this is a high-use server, and taking it down for a few days to figure things out isn't gonna fly very well. As for the question, I'm looking for anything that might be helpful in this situation: a recommendation on a place to find good spares from this era, personal experience repairing RAID volumes using a similar controller or building a hyper-v vm from an old netware server, a line on a floppy with better software for the RAID controller, recommendation on a good Novell consultant in Nebraska that would be able to put things right, a whole other option I haven't considered yet, etc. Update: For backups, we have good (recently verified via restore) backups of the data only -- nothing for the software that actually runs things. Update 2: Just a progress report that I currently have a working Netware 3.12 install in VMWare Virtual Server 2.0, thanks largely to the guide I found here: http://cerbulescubogdan.blogspot.com/2010/11/novell-netware-312-on-vmware.html The next steps are preparing empty netware volumes to match the additional volumes on my existing server, taking a dump of everything on the C:\ drive and netware volumes on my existing server, and figuring out from that information what modules need added to netware, installing my licenses (we do still have that disk, if it's any good), and moving data over. I have approval to bring the server down for a week after the first of the year (sadly not before), so, aside from creating empty volumes, the rest of the work will have to wait until then. Final Update (Jan 5, 2011): I was able to get spares working in both raid arrays without data loss this week. Both are now listed by the controller as "FAULT TOLLERANT" (yay!). I was also able to build on the progress from my last update and now have a functional "spare" server in VMWare Server 2.0. The spare can run and use our erp software, but I can't put it into production because I can't (yet) print from that box (and I have no idea why). Even so, this VM will do in a pinch if I have no other choice, and between it and the repaired RAID arrays I'm comfortable pushing on until I can junk the machine in November.

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• Code Behaviour via Unit Tests

  - by Dewald Galjaard

  Normal 0 false false false EN-ZA X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Some four months ago my car started acting up. Symptoms included a sputtering as my car’s computer switched between gears intermittently. Imagine building up speed, then when you reach 80km/h the car magically and mysteriously decide to switch back to third or even second gear. Clearly it was confused! I managed to track down a technician, an expert in his field to help me out. As he fitted his handheld computer to some hidden port under the dash, he started to explain “These cars are quite intelligent, you know. When they sense something is wrong they run in a restrictive program which probably account for how you managed to drive here in the first place...”  I was surprised and thought this was certainly going to be an interesting test drive. The car ran smoothly down the first couple of stretches as the technician ran through routine checks. Then he said “Ok, all looking good. We need to start testing aspects of the gearbox. Inside the gearbox there are a couple of sensors. One of them is a speed sensor which talks to the computer, which in turn will decide which gear to switch to. The restrictive program avoid these sensors altogether and allow the computer to obtain its input from other [non-affected] sources”. Then, as soon as he forced the speed sensor to come back online the symptoms and ill behaviour re-emerged... What an incredible analogy for getting into a discussion on unit testing software? Besides I should probably put my ill fortune to some good use, right? This example provide a lot of insight into how and why we should conduct unit tests when writing code. More importantly, it captures what is easily and unfortunately often the most overlooked goal of writing unit tests by those new to the art and those who oppose it alike - The goal of writing unit tests is to test the behaviour of our code under predefined conditions. Although it is very possible to test the intrinsic workings of each and every component in your code, writing several tests for each method in practise will soon prove to be an exhausting and ultimately fruitless exercise given the certain and ever changing nature of business requirements. Consequently it is true and quite possible whilst conducting proper unit tests, to call any single method several times as you examine and contemplate different scenarios. Let’s write some code to demonstrate what I mean. In my example I make use of the Moq framework and NUnit to create my tests. Truly you can use whatever you’re comfortable with. First we’ll create an ISpeedSensor interface. This is to represent the speed sensor located in the gearbox.  Then we’ll create a Gearbox class which we’ll pass to a constructor when we instantiate an object of type Computer. All three are described below.   ISpeedSensor.cs namespace AutomaticVehicle {     public interface ISpeedSensor     {         int ReportCurrentSpeed();     } }   Gearbox.cs namespace AutomaticVehicle {      public class Gearbox     {         private ISpeedSensor _speedSensor;           public Gearbox( ISpeedSensor gearboxSpeedSensor )         {             _speedSensor = gearboxSpeedSensor;         }         /// <summary>         /// This method obtain it's reading from the speed sensor.         /// </summary>         /// <returns></returns>         public int ReportCurrentSpeed()         {             return _speedSensor.ReportCurrentSpeed();         }     } } Computer.cs namespace AutomaticVehicle {     public class Computer     {         private Gearbox _gearbox;         public Computer( Gearbox gearbox )         {                     }          public int GetCurrentSpeed()         {             return _gearbox.ReportCurrentSpeed( );         }     } } Since this post is about Unit testing, that is exactly what we’ll create next. Create a second project in your solution. I called mine AutomaticVehicleTests and I immediately referenced the respective nunit, moq and AutomaticVehicle dll’s. We’re going to write a test to examine what happens inside the Computer class. ComputerTests.cs namespace AutomaticVehicleTests {     [TestFixture]     public class ComputerTests     {         [Test]         public void Computer_Gearbox_SpeedSensor_DoesThrow()         {             // Mock ISpeedSensor in gearbox             Mock< ISpeedSensor > speedSensor = new Mock< ISpeedSensor >( );             speedSensor.Setup( n => n.ReportCurrentSpeed() ).Throws<Exception>();             Gearbox gearbox = new Gearbox( speedSensor.Object );               // Create Computer instance to test it's behaviour  towards an exception in gearbox             Computer carComputer = new Computer( gearbox );             // For simplicity let’s assume for now the car only travels at 60 km/h.             Assert.AreEqual( 60, carComputer.GetCurrentSpeed( ) );          }     } }   What is happening in this test? We have created a mocked object using the ISpeedsensor interface which we've passed to our Gearbox object. Notice that I created the mocked object using an interface, not the implementation. I’ll talk more about this in future posts but in short I do this to accentuate the fact that I'm not not really concerned with how SpeedSensor work internally at this particular point in time. Next I’ve gone ahead and created a scenario where I’ve declared the speed sensor in Gearbox to be faulty by forcing it to throw an exception should we ask Gearbox to report on its current speed. Sneaky, sneaky. This test is a simulation of how things may behave in the real world. Inevitability things break, whether it’s caused by mechanical failure, some logical error on your part or a fellow developer which didn’t consult the documentation (or the lack thereof ) - whether you’re calling a speed sensor, making a call to a database, calling a web service or just trying to write a file to disk. It’s a scenario I’ve created and this test is about how the code within the Computer instance will behave towards any such error as I’ve depicted. Now, if you’ve followed closely in my final assert method you would have noticed I did something quite unexpected. I might be getting ahead of myself now but I’m testing to see if the value returned is equal to what I expect it to be under perfect conditions – I’m not testing to see if an error has been thrown! Why is that? Well, in short this is TDD. Test Driven Development is about first writing your test to define the result we want, then to go back and change the implementation within your class to obtain the desired output (I need to make sure I can drive back to the repair shop. Remember? ) So let’s go ahead and run our test as is. It’s fails miserably... Good! Let’s go back to our Computer class and make a small change to the GetCurrentSpeed method.   Computer.cs public int GetCurrentSpeed() {   try   {     return _gearbox.ReportCurrentSpeed( );   }   catch   {     RunRestrictiveProgram( );   } }     This is a simple solution, I know, but it does provide a way to allow for different behaviour. You’re more than welcome to provide an implementation for RunRestrictiveProgram should you feel the need to. It's not within the scope of this post or related to the point I'm trying to make. What is important is to notice how the focus has shifted in our approach from how things can break - to how things behave when broken.   Happy coding!

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• Reinstall ruby (or just yaml lib)

  - by Christian Sciberras

  I've installed ruby 1.9 from source, and tried installing gem 'bundler': < gem install bundler > /usr/local/lib/ruby/1.9.1/yaml.rb:56:in `<top (required)>': > It seems your ruby installation is missing psych (for YAML output). > To eliminate this warning, please install libyaml and reinstall your ruby. > .... I've not been able to cleanly uninstall ruby (wtf?!), and installing libyaml at this point didn't help either. So it seems I've ended up with a fk-ed up server since I can't rollback nor fix the issue. Of course, I do have backups, but this situation is ridiculous nonetheless. Surely there must be a real fix?

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• What are the main differences between SRV records and TXT records?

  - by Chris Adams

  Hi there, I'm trying to consolidate domain names for the servers I look after to just use one panel instead of 3 or 4, and one thing stopping me is that the provider I originally wanted to move them to only lets me the following kinds of records: A MX NS CNAME TXT The first four I understand, but I'm not sure about the relationship (if any) between SRV records and TXT records. Can I use TXT records in the place of SRV records? They both seem to be general text records to just point at a particular server without needing to specify a particular protocol, so it doesn't sound like a totally unreasonable assumption, but I'd rather check here before I break something. If I can only set the above records, does that mean I'm essentially unable to so any SRC record redirecting? Thanks!

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• Do I need a ssl certificate if just pointing my domain to Cloudfront?

  - by hashpipe

  I have a website running on a domain (e.g site.com). I have an additional domain(e.g sitecdn.com) which basically points to Amazon Cloudfront for delivery. Amazon Cloudfront in turn basically fetches the data from the main domain (site.com). I use this setup primarily to have multiple subdomains of my sitecdn.com to point to assets via the cdn. The main website has a ssl certificate, and I intend to put all assets served from the cdn as https links only. Something like <img src="https://img.sitecdn.com/image.jpg" /> I'm a little confused whether I need a ssl for my cdn domain. In cloudfront I can set the setting to allow both https and http traffic. Do I need a ssl certificate for this ? If yes, then where do I install the ssl certificate, since I don't have a server for sitecdn.com.

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• Aironet 1200's Auto-Channel Feature: When should it be used?

  - by Josh Brower

  In our building we have around 25 1200 series Aironets, with a bit of overlap in some areas. Up until this point, we have had them deployed in alternating 1/6/11 channels, but we are wondering if we would get better performance if we used the auto-channel select feature. In looking around, I have seen comments that this feature should not be used as the WAP does a channel scan only on the radio startup, but I have not found this in any Cisco docs. Anybody have anymore information, or real-world experience with this feature? Thanks! -Josh

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