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  • Unable to mount Amazon Public Dataset using ec2-create-volume

    - by the0ther
    I am trying to use a Public Dataset with the snapshot id of snap-­e1608d88. I am looking at these instructions, but they do not seem to help. The first suggestion there says I should click on Volumes and create a new volume, set it's size and availability zone, as well as specifying the snapshot id. The problem is, snapshot id is a dropdown, not a text field, and there are over 100 options in the dropdown. Next I installed the ec2 command line tools and tried to run the ec2-create-volume command. For my first attempt I tried ec2-create-volume --snapshot snap-­e1608d88 --availability-zone us-east-1 but that gave output indicating I need to provide a certificate with the --cert switch. Which certficate exactly? I tried my SSH cert at ~/.ssh/id_rsa. No dice. I got the following Java error: "org.codehaus.xfire.fault.XFireFault: General security error;"

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  • Nginx redirect all request that does not match a file to a php file

    - by cyrbil
    I'm trying to get all request to: http://mydomain.com/downloads/* redirect to http://mydomain.com/downloads/index.php except if the requested file exist in /downloads/ ex: http://mydomain.com/downloads = /downloads/index.php http://mydomain.com/downloads/unknowfile = /downloads/index.php http://mydomain.com/downloads/existingfile = /downloads/existingfile My current problem is I have either the redirection to php working but static files not served or the opposite. Here is my current vhost conf: (which redirect fine but static files are send to php and fail) server { listen 80; ## listen for ipv4; this line is default and implied server_name domain.com; root /data/www; index index.php index.html; location / { try_files $uri $uri/ /index.html; } error_page 404 /404.html; # redirect server error pages to the static page /50x.html error_page 500 502 503 504 /50x.html; location = /50x.html { root /usr/share/nginx/www; } location ^~ /downloads { fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_split_path_info ^(.+\.php)(/.+)$; fastcgi_index index.php; include fastcgi_params; try_files $uri @downloads; } location @downloads { rewrite ^ /downloads/index.php; } # pass the PHP scripts to FastCGI server # location ~ \.php$ { try_files $uri =404; fastcgi_split_path_info ^(.+\.php)(/.+)$; fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_index index.php; include fastcgi_params; } } Precision: static files are symlinks created by /downloads/index.php Thank you for your help.

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  • Forward public port to localhost

    - by Dan
    I have a process running on my Ubuntu 12.04 server that insists on binding to a public IP address. I only want it accessible from localhost, and NOT the outside world. I've been trying to work out a way to forward 1.2.3.4:8888 to 127.0.0.1:8888. I saw something about iptables not wanting to forward connections to loopback, and I haven't been able to make it work with xinetd either. It's also important that the connection not only be available on localhost, but be inaccessible on the interface it's trying to run on. Is this even possible?

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  • Cisco ASA 5505 network route for static IP hosts

    - by TheCapn
    I've configured my internal VLAN using the most basic settings where ports 1-7 are assigned from a pool of addresses in the range 192.168.15.5 - 192.168.15.36. These hosts are given access to the internet and it works great. What I'm trying to set up now is allowing users who are connected to the device and specify their IP (say I connect and request 192.168.15.45) are given internet access and can still work alongside DHCP hosts. Those with a DHCP assigned address are blocked from the internet. Mostly the issue resides in that I am very new to working with the device. I feel that the solution is easy but I'm not looking in the right spots and don't have the correct terminology down to google it. Do I need to define access control lists? Group policies? a new VLAN? The rules that are set up seem to be specific to the entire /24 subnet but when I request a static IP outside of the DHCP range I get blocked from other hosts and the internet.

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  • Accessing Application Server directly by public IP in citrix Farm

    - by EmilioG
    I have an citrix application server in SiteB and I have a Farm in SiteA. We want to add this server into that Farm in SiteB, and access it from the internet via web interface. SiteA and SiteB are connected via VPN. But we would like to do that in a way the ICA traffic goes directly to the application server public IP (behind NAT) in siteB without using siteA and the VPN to route this traffic. Do you know if this is posible? Maybe there is a way to change the host in the ica file for this server in the webinterface (without editing manually each time)? We are using Citrix 4.5. Thanks in advance.

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  • Controlling access to my API using SSH public key (not SSL)

    - by tharrison
    I have the challenge of implementing an API to be consumed by relatively non-technical clients -- pasting some sample code into their WordPress or homegrown PHP site is probably as much as we can ask. Asking them to install SSL on their servers ain't happening. So I am seeking a simple yet secure way to authenticate API clients. OAuth is the obvious solution, but I don't think it passes the "simple" test. Adding a client id and hashed secret as a parameter to the requests is closer -- it's not hard to do md5($secret . $client_id) or whatever the php would be. It seems to me that if client requests could use the same approach as SSH public keys (client gives us a key from their server(s) there should be some existing magic to make all of the subsequent transactions transparently work just as regular HTTP API requests. I am still working this out (obviously :-), so if I am being an idiot, it would be nice to know why. Thanks!

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  • Key-Based SSH Permission denied (publickey) Ubuntu 12-04

    - by user125176
    I have configured sshd to accept key-based ssh logins with LogLevel on DEBUG, and uploaded my public key to ~/.ssh.authorized_keys, where permissions are set as: 700 ~/.ssh 600 ~/.ssh/authorized_keys From root, I can su - USERNAME. From the client I get Permission denied (publicly). From the server Here's how it is telling me that it "Could not open authorized keys '/home/USERNAME/.ssh/authorized_keys': Permission denied". Client protocol version 2.0; client software version OpenSSH_5.2 match: OpenSSH_5.2 pat OpenSSH* Enabling compatibility mode for protocol 2.0 Local version string SSH-2.0-OpenSSH_5.9p1 Debian-5ubuntu1 permanently_set_uid: 105/65534 [preauth] list_hostkey_types: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256 [preauth] SSH2_MSG_KEXINIT sent [preauth] SSH2_MSG_KEXINIT received [preauth] kex: client->server aes128-ctr hmac-md5 none [preauth] kex: server->client aes128-ctr hmac-md5 none [preauth] SSH2_MSG_KEX_DH_GEX_REQUEST received [preauth] SSH2_MSG_KEX_DH_GEX_GROUP sent [preauth] expecting SSH2_MSG_KEX_DH_GEX_INIT [preauth] SSH2_MSG_KEX_DH_GEX_REPLY sent [preauth] SSH2_MSG_NEWKEYS sent [preauth] expecting SSH2_MSG_NEWKEYS [preauth] SSH2_MSG_NEWKEYS received [preauth] KEX done [preauth] userauth-request for user USERNAME service ssh-connection method none [preauth] attempt 0 failures 0 [preauth] PAM: initializing for "USERNAME" PAM: setting PAM_RHOST to "USERHOSTNAME" PAM: setting PAM_TTY to "ssh" userauth_send_banner: sent [preauth] userauth-request for user USERNAME service ssh-connection method publickey [preauth] attempt 1 failures 0 [preauth] test whether pkalg/pkblob are acceptable [preauth] Checking blacklist file /usr/share/ssh/blacklist.RSA-4096 Checking blacklist file /etc/ssh/blacklist.RSA-4096 temporarily_use_uid: 1001/1002 (e=0/0) trying public key file /home/USERNAME/.ssh/authorized_keys Could not open authorized keys '/home/USERNAME/.ssh/authorized_keys': Permission denied restore_uid: 0/0 temporarily_use_uid: 1001/1002 (e=0/0) trying public key file /home/USERNAME/.ssh/authorized_keys2 Could not open authorized keys '/home/USERNAME/.ssh/authorized_keys2': Permission denied restore_uid: 0/0 Failed publickey for USERNAME from IPADDRESS port 57523 ssh2 Connection closed by IPADDRESS [preauth] do_cleanup [preauth] monitor_read_log: child log fd closed do_cleanup PAM: cleanup

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  • RPM issues after signing JDK 1.6 64-bit

    - by organicveggie
    I'm trying to sign the Java JDK 1.6u21 64-bit RPM on CentOS 5.5 for use with Spacewalk and I'm running into problems. It seems to sign okay, but then when I check the signature it seems to be missing the key I just used to sign it. Yet RPM shows the key in it's list... # rpm --addsign jdk-6u21-linux-amd64.rpm Enter pass phrase: Pass phrase is good. jdk-6u21-linux-amd64.rpm: gpg: WARNING: standard input reopened gpg: WARNING: standard input reopened # rpm --checksig -v jdk-6u21-linux-amd64.rpm jdk-6u21-linux-amd64.rpm: Header V3 DSA signature: NOKEY, key ID ecfd98a5 MD5 digest: OK (650e0961e20d4a44169b68e8f4a1691b) V3 DSA signature: OK, key ID ecfd98a5 Yet I have the key imported (edited for privacy): # rpm -qa gpg-pubkey* |grep ecfd98a5 gpg-pubkey-ecfd98a5-4caa4a4c # rpm -qi gpg-pubkey-ecfd98a5-4caa4a4c Name : gpg-pubkey Relocations: (not relocatable) Version : ecfd98a5 Vendor: (none) Release : 4caa4a4c Build Date: Mon 04 Oct 2010 10:20:49 PM CDT Install Date: Mon 04 Oct 2010 10:20:49 PM CDT Build Host: localhost Group : Public Keys Source RPM: (none) Size : 0 License: pubkey Signature : (none) Summary : gpg(FirstName LastName <[email protected]>) Description : -----BEGIN PGP PUBLIC KEY BLOCK----- Version: rpm-4.4.2.3 (NSS-3) ...key goes here... =gKjN-----END PGP PUBLIC KEY BLOCK----- And I'm definitely running a 64-bit version of CentOS: # uname -a Linux spacewalk.mycompany.corp 2.6.18-194.11.4.el5 #1 SMP Tue Sep 21 05:04:09 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux Without a valid signature, Spacewalk refuses to install the RPM unless I completely disable signature checking. I have tried this with two different keys and two different users on the same machine without any success. Any bright ideas?

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  • Is it ok to share private key file between multiple computers/services?

    - by Behrang
    So we all know how to use public key/private keys using SSH, etc. But what's the best way to use/reuse them? Should I keep them in a safe place forever? I mean, I needed a pair of keys for accessing GitHub. I created a pair from scratch and used that for some time to access GitHub. Then I formatted my HDD and lost that pair. Big deal, I created a new pair and configured GitHub to use my new pair. Or is it something that I don't want to lose? I also needed a pair of public key/private keys to access our company systems. Our admin asked me for my public key and I generated a new pair and gave it to him. Is it generally better to create a new pair for access to different systems or is it better to have one pair and reuse it to access different systems? Similarly, is it better to create two different pairs and use one to access our companies systems from home and the other one to access the systems from work, or is it better to just have one pair and use it from both places?

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  • Using TaskDialogIndirect in C#

    - by Dennis Delimarsky
    I've been working for a while with the regular Windows Vista/7 TaskDialog for a while, and I wanted to add some additional functionality (like custom buttons and a footer), so I need to use TaskDialogIndirect. Following the MSDN documentation for TaskDialogIndirect, I got this signature: [DllImport("comctl32.dll",CharSet = CharSet.Unicode,EntryPoint="TaskDialogIndirect")] static extern int TaskDialogIndirect (TASKDIALOGCONFIG pTaskConfig, out int pnButton, out int pnRadioButton, out bool pfVerificationFlagChecked); The TASKDIALOGCONFIG class is shown below: public class TASKDIALOGCONFIG { public UInt16 cbSize; public IntPtr hwndParent; public IntPtr hInstance; public String dwFlags; public String dwCommonButtons; public IntPtr hMainIcon; public String pszMainIcon; public String pszMainInstruction; public String pszContent; public UInt16 cButtons; public TASKDIALOG_BUTTON pButtons; public int nDefaultButton; public UInt16 cRadioButtons; public TASKDIALOG_BUTTON pRadioButtons; public int nDefaultRadioButton; public String pszVerificationText; public String pszExpandedInformation; public String pszExpandedControlText; public String pszCollapsedControlText; public IntPtr hFooterIcon; public IntPtr pszFooterText; public String pszFooter; // pfCallback; // lpCallbackData; public UInt16 cxWidth; } The TASKDIALOG_BUTTON implementation: public class TASKDIALOG_BUTTON { public int nButtonID; public String pszButtonText; } I am not entirely sure if I am on the right track here. Did anyone use TaskDialogIndirect from managed code directly through WinAPI (without VistaBridge or Windows API Code Pack)? I am curious about the possible implementations, as well as the callback declarations (I am not entirely sure how to implement TaskDialogCallbackProc). PS: I am looking for a direct WinAPI implementation, not one through a wrapper.

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  • Converting 2D Physics to 3D.

    - by static void main
    I'm new to game physics and I am trying to adapt a simple 2D ball simulation for a 3D simulation with the Java3D library. I have this problem: Two things: 1) I noted down the values generated by the engine: X/Y are too high and minX/minY/maxY/maxX values are causing trouble. Sometimes the balls are drawing but not moving Sometimes they are going out of the panel Sometimes they're moving on little area Sometimes they just stick at one place... 2) I'm unable to select/define/set the default correct/suitable values considering the 3D graphics scaling/resolution while they are set with respect to 2D screen coordinates, that is my only problem. Please help. This is the code: public class Ball extends GameObject { private float x, y; // Ball's center (x, y) private float speedX, speedY; // Ball's speed per step in x and y private float radius; // Ball's radius // Collision detected by collision detection and response algorithm? boolean collisionDetected = false; // If collision detected, the next state of the ball. // Otherwise, meaningless. private float nextX, nextY; private float nextSpeedX, nextSpeedY; private static final float BOX_WIDTH = 640; private static final float BOX_HEIGHT = 480; /** * Constructor The velocity is specified in polar coordinates of speed and * moveAngle (for user friendliness), in Graphics coordinates with an * inverted y-axis. */ public Ball(String name1,float x, float y, float radius, float speed, float angleInDegree, Color color) { this.x = x; this.y = y; // Convert velocity from polar to rectangular x and y. this.speedX = speed * (float) Math.cos(Math.toRadians(angleInDegree)); this.speedY = speed * (float) Math.sin(Math.toRadians(angleInDegree)); this.radius = radius; } public void move() { if (collisionDetected) { // Collision detected, use the values computed. x = nextX; y = nextY; speedX = nextSpeedX; speedY = nextSpeedY; } else { // No collision, move one step and no change in speed. x += speedX; y += speedY; } collisionDetected = false; // Clear the flag for the next step } public void collideWith() { // Get the ball's bounds, offset by the radius of the ball float minX = 0.0f + radius; float minY = 0.0f + radius; float maxX = 0.0f + BOX_WIDTH - 1.0f - radius; float maxY = 0.0f + BOX_HEIGHT - 1.0f - radius; double gravAmount = 0.9811111f; double gravDir = (90 / 57.2960285258); // Try moving one full step nextX = x + speedX; nextY = y + speedY; System.out.println("In serializedBall in collision."); // If collision detected. Reflect on the x or/and y axis // and place the ball at the point of impact. if (speedX != 0) { if (nextX > maxX) { // Check maximum-X bound collisionDetected = true; nextSpeedX = -speedX; // Reflect nextSpeedY = speedY; // Same nextX = maxX; nextY = (maxX - x) * speedY / speedX + y; // speedX non-zero } else if (nextX < minX) { // Check minimum-X bound collisionDetected = true; nextSpeedX = -speedX; // Reflect nextSpeedY = speedY; // Same nextX = minX; nextY = (minX - x) * speedY / speedX + y; // speedX non-zero } } // In case the ball runs over both the borders. if (speedY != 0) { if (nextY > maxY) { // Check maximum-Y bound collisionDetected = true; nextSpeedX = speedX; // Same nextSpeedY = -speedY; // Reflect nextY = maxY; nextX = (maxY - y) * speedX / speedY + x; // speedY non-zero } else if (nextY < minY) { // Check minimum-Y bound collisionDetected = true; nextSpeedX = speedX; // Same nextSpeedY = -speedY; // Reflect nextY = minY; nextX = (minY - y) * speedX / speedY + x; // speedY non-zero } } speedX += Math.cos(gravDir) * gravAmount; speedY += Math.sin(gravDir) * gravAmount; } public float getSpeed() { return (float) Math.sqrt(speedX * speedX + speedY * speedY); } public float getMoveAngle() { return (float) Math.toDegrees(Math.atan2(speedY, speedX)); } public float getRadius() { return radius; } public float getX() { return x; } public float getY() { return y; } public void setX(float f) { x = f; } public void setY(float f) { y = f; } } Here's how I'm drawing the balls: public class 3DMovingBodies extends Applet implements Runnable { private static final int BOX_WIDTH = 800; private static final int BOX_HEIGHT = 600; private int currentNumBalls = 1; // number currently active private volatile boolean playing; private long mFrameDelay; private JFrame frame; private int currentFrameRate; private Ball[] ball = new Ball[currentNumBalls]; private Random rand; private Sphere[] sphere = new Sphere[currentNumBalls]; private Transform3D[] trans = new Transform3D[currentNumBalls]; private TransformGroup[] objTrans = new TransformGroup[currentNumBalls]; public 3DMovingBodies() { rand = new Random(); float angleInDegree = rand.nextInt(360); setLayout(new BorderLayout()); GraphicsConfiguration config = SimpleUniverse .getPreferredConfiguration(); Canvas3D c = new Canvas3D(config); add("Center", c); ball[0] = new Ball(0.5f, 0.0f, 0.5f, 0.4f, angleInDegree, Color.yellow); // ball[1] = new Ball(1.0f, 0.0f, 0.25f, 0.8f, angleInDegree, // Color.yellow); // ball[2] = new Ball(0.0f, 1.0f, 0.15f, 0.11f, angleInDegree, // Color.yellow); trans[0] = new Transform3D(); // trans[1] = new Transform3D(); // trans[2] = new Transform3D(); sphere[0] = new Sphere(0.5f); // sphere[1] = new Sphere(0.25f); // sphere[2] = new Sphere(0.15f); // Create a simple scene and attach it to the virtual universe BranchGroup scene = createSceneGraph(); SimpleUniverse u = new SimpleUniverse(c); u.getViewingPlatform().setNominalViewingTransform(); u.addBranchGraph(scene); startSimulation(); } public BranchGroup createSceneGraph() { // Create the root of the branch graph BranchGroup objRoot = new BranchGroup(); for (int i = 0; i < currentNumBalls; i++) { // Create a simple shape leaf node, add it to the scene graph. objTrans[i] = new TransformGroup(); objTrans[i].setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE); Transform3D pos1 = new Transform3D(); pos1.setTranslation(randomPos()); objTrans[i].setTransform(pos1); objTrans[i].addChild(sphere[i]); objRoot.addChild(objTrans[i]); } BoundingSphere bounds = new BoundingSphere(new Point3d(0.0, 0.0, 0.0), 100.0); Color3f light1Color = new Color3f(1.0f, 0.0f, 0.2f); Vector3f light1Direction = new Vector3f(4.0f, -7.0f, -12.0f); DirectionalLight light1 = new DirectionalLight(light1Color, light1Direction); light1.setInfluencingBounds(bounds); objRoot.addChild(light1); // Set up the ambient light Color3f ambientColor = new Color3f(1.0f, 1.0f, 1.0f); AmbientLight ambientLightNode = new AmbientLight(ambientColor); ambientLightNode.setInfluencingBounds(bounds); objRoot.addChild(ambientLightNode); return objRoot; } public void startSimulation() { playing = true; Thread t = new Thread(this); t.start(); } public void stop() { playing = false; } public void run() { long previousTime = System.currentTimeMillis(); long currentTime = previousTime; long elapsedTime; long totalElapsedTime = 0; int frameCount = 0; while (true) { currentTime = System.currentTimeMillis(); elapsedTime = (currentTime - previousTime); // elapsed time in // seconds totalElapsedTime += elapsedTime; if (totalElapsedTime > 1000) { currentFrameRate = frameCount; frameCount = 0; totalElapsedTime = 0; } for (int i = 0; i < currentNumBalls; i++) { ball[i].move(); ball[i].collideWith(); drawworld(); } try { Thread.sleep(88); } catch (Exception e) { e.printStackTrace(); } previousTime = currentTime; frameCount++; } } public void drawworld() { for (int i = 0; i < currentNumBalls; i++) { printTG(objTrans[i], "SteerTG"); trans[i].setTranslation(new Vector3f(ball[i].getX(), ball[i].getY(), 0.0f)); objTrans[i].setTransform(trans[i]); } } private Vector3f randomPos() /* * Return a random position vector. The numbers are hardwired to be within * the confines of the box. */ { Vector3f pos = new Vector3f(); pos.x = rand.nextFloat() * 5.0f - 2.5f; // -2.5 to 2.5 pos.y = rand.nextFloat() * 2.0f + 0.5f; // 0.5 to 2.5 pos.z = rand.nextFloat() * 5.0f - 2.5f; // -2.5 to 2.5 return pos; } // end of randomPos() public static void main(String[] args) { System.out.println("Program Started"); 3DMovingBodiesbb = new 3DMovingBodies(); bb.addKeyListener(bb); MainFrame mf = new MainFrame(bb, 600, 400); } }

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  • LibGDX onTouch() method Array and flip method

    - by johnny-b
    How can I add this on my application. i want to use the onTouch() method from the implementation of the InputProcessor to kill the enemies on screen. how do i do that? do i have to do anything to the enemy class? also i am trying to add a Array of enemies and it keeps throwing exceptions or the bullet now is facing LEFT <--- again after I used the flip method in the bullet class. All the code is below so please anyone feel free to have a look thanks. please help Thank you M // This is the bullet class. public class Bullet extends Sprite { public static final float BULLET_HOMING = 6000; public static final float BULLET_SPEED = 300; private Vector2 velocity; private float lifetime; private Rectangle bul; public Bullet(float x, float y) { velocity = new Vector2(0, 0); setPosition(x, y); AssetLoader.bullet1.flip(true, false); AssetLoader.bullet2.flip(true, false); setSize(AssetLoader.bullet1.getWidth(), AssetLoader.bullet1.getHeight()); bul = new Rectangle(); } public void update(float delta) { float targetX = GameWorld.getBall().getX(); float targetY = GameWorld.getBall().getY(); float dx = targetX - getX(); float dy = targetY - getY(); float distToTarget = (float) Math.sqrt(dx * dx + dy * dy); dx /= distToTarget; dy /= distToTarget; dx *= BULLET_HOMING; dy *= BULLET_HOMING; velocity.x += dx * delta; velocity.y += dy * delta; float vMag = (float) Math.sqrt(velocity.x * velocity.x + velocity.y * velocity.y); velocity.x /= vMag; velocity.y /= vMag; velocity.x *= BULLET_SPEED; velocity.y *= BULLET_SPEED; bul.set(getX(), getY(), getOriginX(), getOriginY()); Vector2 v = velocity.cpy().scl(delta); setPosition(getX() + v.x, getY() + v.y); setOriginCenter(); setRotation(velocity.angle()); } public Rectangle getBounds() { return bul; } public Rectangle getBounds1() { return this.getBoundingRectangle(); } } // This is the class where i load all the images from public class AssetLoader { public static Texture texture; public static TextureRegion bg, ball1, ball2; public static Animation bulletAnimation, ballAnimation; public static Sprite bullet1, bullet2; public static void load() { texture = new Texture(Gdx.files.internal("SpriteN1.png")); texture.setFilter(TextureFilter.Nearest, TextureFilter.Nearest); bg = new TextureRegion(texture, 80, 421, 395, 30); bg.flip(false, true); ball1 = new TextureRegion(texture, 0, 321, 32, 32); ball1.flip(false, true); ball2 = new TextureRegion(texture, 32, 321, 32, 32); ball2.flip(false, true); bullet1 = new Sprite(texture, 380, 350, 45, 20); bullet1.flip(false, true); bullet2 = new Sprite(texture, 425, 350, 45, 20); bullet2.flip(false, true); TextureRegion[] balls = { ball1, ball2 }; ballAnimation = new Animation(0.16f, balls); ballAnimation.setPlayMode(Animation.PlayMode.LOOP); } Sprite[] bullets = { bullet1, bullet2 }; bulletAnimation = new Animation(0.06f, aims); bulletAnimation.setPlayMode(Animation.PlayMode.LOOP); } public static void dispose() { texture.dispose(); } // This is for the rendering or drawing onto the screen/canvas. public class GameRenderer { private Bullet bullet; private Ball ball; public GameRenderer(GameWorld world) { myWorld = world; cam = new OrthographicCamera(); cam.setToOrtho(true, 480, 320); batcher = new SpriteBatch(); // Attach batcher to camera batcher.setProjectionMatrix(cam.combined); shapeRenderer = new ShapeRenderer(); shapeRenderer.setProjectionMatrix(cam.combined); // Call helper methods to initialize instance variables initGameObjects(); initAssets(); } private void initGameObjects() { ball = GameWorld.getBall(); bullet = myWorld.getBullet(); scroller = myWorld.getScroller(); } private void initAssets() { ballAnimation = AssetLoader.ballAnimation; bulletAnimation = AssetLoader.bulletAnimation; } public void render(float runTime) { Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT); batcher.begin(); batcher.disableBlending(); batcher.enableBlending(); batcher.draw(AssetLoader.ballAnimation.getKeyFrame(runTime), ball.getX(), ball.getY(), ball.getWidth(), ball.getHeight()); batcher.draw(AssetLoader.bulletAnimation.getKeyFrame(runTime), bullet.getX(), bullet.getY(), bullet.getOriginX(), bullet.getOriginY(), bullet.getWidth(), bullet.getHeight(), 1.0f, 1.0f, bullet.getRotation()); // End SpriteBatch batcher.end(); } } // this is to load the image etc on the screen i guess public class GameWorld { public static Ball ball; private Bullet bullet; private ScrollHandler scroller; public GameWorld() { ball = new Ball(480, 273, 32, 32); bullet = new Bullet(10, 10); scroller = new ScrollHandler(0); } public void update(float delta) { ball.update(delta); bullet.update(delta); scroller.update(delta); } public static Ball getBall() { return ball; } public ScrollHandler getScroller() { return scroller; } public Bullet getBullet() { return bullet; } } //This is the input handler class public class InputHandler implements InputProcessor { private Ball myBall; private Bullet bullet; private GameRenderer aims; // Ask for a reference to the Soldier when InputHandler is created. public InputHandler(Ball ball) { myBall = ball; } @Override public boolean touchDown(int screenX, int screenY, int pointer, int button) { return false; } @Override public boolean keyDown(int keycode) { return false; } @Override public boolean keyUp(int keycode) { return false; } @Override public boolean keyTyped(char character) { return false; } @Override public boolean touchUp(int screenX, int screenY, int pointer, int button) { return false; } @Override public boolean touchDragged(int screenX, int screenY, int pointer) { return false; } @Override public boolean mouseMoved(int screenX, int screenY) { return false; } @Override public boolean scrolled(int amount) { return false; } } i am rendering all graphics in a GameRender class and a gameworld class if you need more info please let me know I am trying to make the array work but keep finding that when an array is initialized then the bullet fips back to the original and ends up being backwards???? and if I create an array I keep getting Exceptions throw??? Thank you for any help given.

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  • Pxe net install Centos with Static IP

    - by Stu2000
    I seem to be unable to perform a kickstart installation of centos5.8 with a netinstall. It correctly gets into the text installer, but keeps sending out a request for the dhcp server and failing. I have tried to manually set the IP everywhere. Here is my pxelinux.cfg file DEFAULT menu PROMPT 0 MENU TITLE Ubuntu MAAS TIMEOUT 200 TOTALTIMEOUT 6000 ONTIMEOUT local LABEL centos5.8-net kernel /images/centos5.8-net/vmlinuz MENU LABEL centos5.8-net append initrd=/images/centos5.8-net/initrd.img ip=192.168.1.163 netmask=255.255.255.0 hostname=client101 gateway=192.168.1.1 ksdevice=eth0 dns=8.8.8.8 ks=http://192.168.1.125/cblr/svc/op/ks/profile/centos5.8-net MENU end and here is my kickstart file: # Kickstart file for a very basic Centos 5.8 system # Assigns the server ip: 192.211.48.163 # DNS 8.8.8.8, 8.8.4.4 # London TZ install url --url http://mirror.centos.org/centos-5/5.8/os/i386 lang en_US.UTF-8 keyboard us network --device=eth0 --bootproto=static --ip=192.168.1.163 --netmask=255.255.255.0 --gateway=192.168.1.1 --nameserver=8.8.8.8,8.8.4.4 --hostname=client1-server --onboot=on rootpw --iscrypted $1$Snrd2bB6$CuD/07AX2r/lHgVTPZyAz/ firewall --enabled --port=22:tcp authconfig --enableshadow --enablemd5 selinux --enforcing timezone --utc Europe/London bootloader --location=mbr --driveorder=xvda --append="console=xvc0" # The following is the partition information you requested # Note that any partitions you deleted are not expressed # here so unless you clear all partitions first, this is # not guaranteed to work part /boot --fstype ext3 --size=100 --ondisk=xvda part pv.2 --size=0 --grow --ondisk=xvda volgroup VolGroup00 --pesize=32768 pv.2 logvol swap --fstype swap --name=LogVol01 --vgname=VolGroup00 --size=528 --grow --maxsize=1056 logvol / --fstype ext3 --name=LogVol00 --vgname=VolGroup00 --size=1024 --grow %packages @base @core @dialup @editors @text-internet keyutils iscsi-initiator-utils trousers bridge-utils fipscheck device-mapper-multipath sgpio emacs Here is my dhcp file: ddns-update-style interim; allow booting; allow bootp; ignore client-updates; set vendorclass = option vendor-class-identifier; subnet 192.168.1.0 netmask 255.255.255.0 { host tower { hardware ethernet 50:E5:49:18:D5:C6; fixed-address 192.168.1.163; option routers 192.168.1.1; option domain-name-servers 8.8.8.8,8.8.4.4; option subnet-mask 255.255.255.0; filename "/pxelinux.0"; default-lease-time 21600; max-lease-time 43200; next-server 192.168.1.125; } } Is it impossible to prevent it asking for a dynamic ip before trying to install from the net? Perhaps there is an error in of my files? My dhcp server is set to ignore client-updates, and is set to only works with one mac address whilst testing.

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  • Nginx + Wordpress Multisite 3.4.2 + subdirectories + static pages and permalinks

    - by UrkoM
    I am trying to setup Wordpress Multisite, using subdirectories, with Nginx, php5-fpm, APC, and Batcache. As many other people, I am getting stuck in the rewrite rules for permalinks. I have followed these two guides, which seem to be as official as you can get: http://evansolomon.me/notes/faster-wordpress-multisite-nginx-batcache/ http://codex.wordpress.org/Nginx#WordPress_Multisite_Subdirectory_rules It is partially working: http://blog.ssis.edu.vn works. http://blog.ssis.edu.vn/umasse/ works. But other permalinks, like these two to a post or to a static page, don't work: http://blog.ssis.edu.vn/umasse/2008/12/12/hello-world-2/ http://blog.ssis.edu.vn/umasse/sample-page/ They either take you to a 404 error, or to some other blog! Here is my configuration: server { listen 80 default_server; server_name blog.ssis.edu.vn; root /var/www; access_log /var/log/nginx/blog-access.log; error_log /var/log/nginx/blog-error.log; location / { index index.php; try_files $uri $uri/ /index.php?$args; } # Add trailing slash to */wp-admin requests. rewrite /wp-admin$ $scheme://$host$uri/ permanent; # Add trailing slash to */username requests rewrite ^/[_0-9a-zA-Z-]+$ $scheme://$host$uri/ permanent; # Directives to send expires headers and turn off 404 error logging. location ~* \.(js|css|png|jpg|jpeg|gif|ico)$ { expires 24h; log_not_found off; } # this prevents hidden files (beginning with a period) from being served location ~ /\. { access_log off; log_not_found off; deny all; } # Pass uploaded files to wp-includes/ms-files.php. rewrite /files/$ /index.php last; if ($uri !~ wp-content/plugins) { rewrite /files/(.+)$ /wp-includes/ms-files.php?file=$1 last; } # Rewrite multisite '.../wp-.*' and '.../*.php'. if (!-e $request_filename) { rewrite ^/[_0-9a-zA-Z-]+(/wp-.*) $1 last; rewrite ^/[_0-9a-zA-Z-]+.*(/wp-admin/.*\.php)$ $1 last; rewrite ^/[_0-9a-zA-Z-]+(/.*\.php)$ $1 last; } location ~ \.php$ { # Forbid PHP on upload dirs if ($uri ~ "uploads") { return 403; } client_max_body_size 25M; try_files $uri =404; fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; include /etc/nginx/fastcgi_params; } } Any ideas are welcome! Have I done something wrong? I have disabled Batcache to see if it makes any difference, but still no go.

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  • Nullpointerexcption & abrupt IOStream closure with inheritence and subclasses

    - by user1401652
    A brief background before so we can communicate on the same wave length. I've had about 8-10 university courses on programming from data structure, to one on all languages, to specific ones such as java & c++. I'm a bit rusty because i usually take 2-3 month breaks from coding. This is a personal project that I started thinking of two years back. Okay down to the details, and a specific question, I'm having problems with my mutator functions. It seems to be that I am trying to access a private variable incorrectly. The question is, am I nesting my classes too much and trying to mutate a base class variable the incorrect way. If so point me in the way of the correct literature, or confirm this is my problem so I can restudy this information. Thanks package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Date { private int hour, minute, day, month, year; Date() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What's the hour? (Use 1-24 military notation"); hour = Integer.parseInt(keyboard.readLine()); System.out.println("what's the minute? "); minute = Integer.parseInt(keyboard.readLine()); System.out.println("What's the day of the month?"); day = Integer.parseInt(keyboard.readLine()); System.out.println("Which month of the year is it, use an integer"); month = Integer.parseInt(keyboard.readLine()); System.out.println("What year is it?"); year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (IOException e) { System.out.println("Yo houston we have a problem"); } } public void setHour(int hour) { this.hour = hour; } public void setHour() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What hour, use military notation?"); this.hour = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getHour() { return hour; } public void setMinute(int minute) { this.minute = minute; } public void setMinute() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What minute?"); this.minute = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ": doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": minute shall not cooperate"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the setMinute function of the Date class"); } } public int getMinute() { return minute; } public void setDay(int day) { this.day = day; } public void setDay() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What day 0-6?"); this.day = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getDay() { return day; } public void setMonth(int month) { this.month = month; } public void setMonth() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What month 0-11?"); this.month = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getMonth() { return month; } public void setYear(int year) { this.year = year; } public void setYear() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What year?"); this.year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getYear() { return year; } public void set() { setMinute(); setHour(); setDay(); setMonth(); setYear(); } public Vector<Integer> get() { Vector<Integer> holder = new Vector<Integer>(5); holder.add(hour); holder.add(minute); holder.add(month); holder.add(day); holder.add(year); return holder; } }; That is the Date class obviously, next is the other base class Location. package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Location { String streetName, state, city, country; int zipCode, address; Location() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What is the street name"); streetName = keyboard.readLine(); System.out.println("Which state?"); state = keyboard.readLine(); System.out.println("Which city?"); city = keyboard.readLine(); System.out.println("Which country?"); country = keyboard.readLine(); System.out.println("Which zipcode?");//if not u.s. continue around this step zipCode = Integer.parseInt(keyboard.readLine()); System.out.println("What address?"); address = Integer.parseInt(keyboard.readLine()); } catch (IOException e) { System.out.println(e.toString()); } } public void setZipCode(int zipCode) { this.zipCode = zipCode; } public void setZipCode() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What zipCode?"); this.zipCode = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public void set() { setAddress(); setCity(); setCountry(); setState(); setStreetName(); setZipCode(); } public int getZipCode() { return zipCode; } public void setAddress(int address) { this.address = address; } public void setAddress() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.address = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getAddress() { return address; } public void setStreetName(String streetName) { this.streetName = streetName; } public void setStreetName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.streetName = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getStreetName() { return streetName; } public void setState(String state) { this.state = state; } public void setState() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.state = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getState() { return state; } public void setCity(String city) { this.city = city; } public void setCity() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.city = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCity() { return city; } public void setCountry(String country) { this.country = country; } public void setCountry() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.country = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCountry() { return country; } }; their parent(What is the proper name?) class package GroceryReceiptProgram; import java.io.*; public class FoodGroup { private int price, count; private Date purchaseDate, expirationDate; private Location location; private String name; public FoodGroup() { try { setPrice(); setCount(); expirationDate.set(); purchaseDate.set(); location.set(); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the constructor of the FoodGroup class"); } } public void setPrice(int price) { this.price = price; } public void setPrice() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What Price?"); price = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setPrice function"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class. SetPrice()"); } } public int getPrice() { return price; } public void setCount(int count) { this.count = count; } public void setCount() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What count?"); count = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setCount()"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class, setCount"); } } public int getCount() { return count; } public void setName(String name) { this.name = name; } public void setName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.name = keyboard.readLine(); } catch (IOException e) { System.out.println(e.toString()); } } public String getName() { return name; } public void setLocation(Location location) { this.location = location; } public Location getLocation() { return location; } public void setPurchaseDate(Date purchaseDate) { this.purchaseDate = purchaseDate; } public void setPurchaseDate() { this.purchaseDate.set(); } public Date getPurchaseDate() { return purchaseDate; } public void setExpirationDate(Date expirationDate) { this.expirationDate = expirationDate; } public void setExpirationDate() { this.expirationDate.set(); } public Date getExpirationDate() { return expirationDate; } } and finally the main class, so I can get access to all of this work. package GroceryReceiptProgram; public class NewMain { public static void main(String[] args) { FoodGroup test = new FoodGroup(); } } If anyone is further interested, here is a link the UML for this. https://www.dropbox.com/s/1weigjnxih70tbv/GRP.dia

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  • Can't get SSH public key authentication to work

    - by Trey Parkman
    My server is running CentOS 5.3. I'm on a Mac running Leopard. I don't know which is responsible for this: I can log on to my server just fine via password authentication. I've gone through all of the steps for setting up PKA (as described at http://www.centos.org/docs/5/html/Deployment_Guide-en-US/s1-ssh-beyondshell.html), but when I use SSH, it refuses to even attempt publickey verification. Using the command ssh -vvv user@host (where -vvv cranks up verbosity to the maximum level) I get the following relevant output: debug2: key: /Users/me/.ssh/id_dsa (0x123456) debug1: Authentications that can continue: publickey,gssapi-with-mic,password debug3: start over, passed a different list publickey,gssapi-with-mic,password debug3: preferred keyboard-interactive,password debug3: authmethod_lookup password debug3: remaining preferred: ,password debug3: authmethod_is_enabled password debug1: Next authentication method: password followed by a prompt for my password. If I try to force the issue with ssh -vvv -o PreferredAuthentications=publickey user@host I get debug2: key: /Users/me/.ssh/id_dsa (0x123456) debug1: Authentications that can continue: publickey,gssapi-with-mic,password debug3: start over, passed a different list publickey,gssapi-with-mic,password debug3: preferred publickey debug3: authmethod_lookup publickey debug3: No more authentication methods to try. So, even though the server says it accepts the publickey authentication method, and my SSH client insists on it, I'm rebutted. (Note the conspicuous absence of an "Offering public key:" line above.) Any suggestions?

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  • Cisco ASA and static IPv6 tunnel endpoint?

    - by Martijn Heemels
    I recently installed a Cisco ASA 5505 firewall on the edge of our LAN. The setup is simple: Internet <-- ASA <-- LAN I would like provide the hosts in the LAN with IPv6 connectivity by setting up a 6in4 tunnel to SixXS. It would be nice to have the ASA as tunnel endpoint so it can firewall both IPv4 and IPv6 traffic. Unfortunately the ASA apparently can't create a tunnel itself, and can't port-forward protocol 41 traffic, so I believe I would have to do one of the following instead: Set up a host with it's own IP outside the firewall, and have that function as tunnel-endpoint. The ASA can then firewall and route the v6 subnet to the LAN. Set up a host inside the firewall that functions as endpoint, separated via vlan or whatever, and loop the traffic back into the ASA where it can be firewalled and routed. This seems contrived, but would allow me to use a VM instead of a physical machine as endpoint. Any other way? What would you suggest is the optimal way to set this up? P.S. I do have a spare public IP address available if needed, and can spin up another VM in our VMware infrastructure.

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  • Using bind (named) as a public proxy server

    - by TrentDavis
    We have a Python DNS server that does a bunch of stuff to figure out values it should return for various DNS records. This works nicely, however as it is Python, the performance under high load won't be great. What I would like to do is have a "proxy" bind server sit in front of it to return results to the public internet. This will cache the results (typically 15 minutes, some records are a few seconds), so the load on the Python server will be greatly reduced as it will only see one look up per domain (only about 100 domains) every 15 minutes. The data in these domains changes a lot, so using a master won't work as it will constantly be changing. I have something setup that looked like it would work great (using a forwarder for the zone), and tested it with dig etc, all going great. However when we went to go live with it, things weren't working, and we figured out that named is not setting the "Authoritative" bit (fair enough, it is a forwarder). So my question is, can we tell bind to set the Authoritative bit for forwarded domains? I have looked at all the doco I can find, and can't find anything about doing things this way. Most of the doco about using it as a proxy if for a LAN to the internet. Ideally I would like to use bind as it is there and installed (CentOS 5 servers). But at a pinch we could look at a different name server to do the work if it just can't be done with bind. Thanks.

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  • Network config for KVM on physical machine with single NIC and single public IP

    - by neo0
    I have a physical machine running CentOS 6.4 and I will rent a place to run it in a data center. I want to install KVM on that machine to run some virtual machines. The problem is my physical machine have only one NIC and the data center give me a public IP for that interface. So how should I configure network on the physical machine to make it assign for each vm a private IP that can connect to Internet. If I create a br0 bridged with eth0 interface and create a vm with option --bridge=br0 then KVM could not assign an IP for the vm so setup can not be done. Should I use NAT mode? Does KVM have any host-only network like Virtualbox? But the vm still has to connect to outside? Thank you! Update I install the guest network using NAT (--network network:default) and then I only have to port-forwarding from the host. But if I config br0 bridged with physical eth0 then the guest can not get an IP from boot. So I removed the br0 and it worked.

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  • Rapidly changing public IP addresses on certain networks?

    - by zenblender
    I run/develop an online game where many of our users are in southeast asia. I recently went to southeast asia and made an alarming discovery. Anywhere I got internet access, whether it was via 3G, a LAN in a hotel, or wifi in a cafe, both in Singapore and the Philippines, I noticed that my IP address was changing CONSTANTLY. I mean the public IP address, not the private one. I could load a page like whatismyip.com and just hit reload and see a new IP address show up every 5-10 seconds! This has lots of consequences for my online game, as many things "break" if the IP address changes for a given user. Basically, I would like to know more about this. Is there a name for the kind of network or router or paradigm that causes this, so I can read up on it? I don't understand WHY a network would function this way. Does it do this on purpose? Is it for security reasons? Is it to anonymize and protect the identity of the users? Or is it just an "old" method that is mostly obsolete in the rest of the world? Thanks for any info that will help me to understand.

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  • What can Haskell's type system do that Java's can't?

    - by Matt Fenwick
    I was talking to a friend about the differences between the type systems of Haskell and Java. He asked me what Haskell's could do that Java's couldn't, and I realized that I didn't know. After thinking for a while, I came up with a very short list of minor differences. Not being heavy into type theory, I'm left wondering whether they're formally equivalent. To try and keep this from becoming a subjective question, I'm asking: what are the major, non-syntactical differences between their type systems? I realize some things are easier/harder in one than in the other, and I'm not interested in talking about those. And to make it more specific, let's ignore Haskell type extensions since there's so many out there that do all kinds of crazy/cool stuff.

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  • What can Haskell's type system do that Java's can't and vice versa?

    - by Matt Fenwick
    I was talking to a friend about the differences between the type systems of Haskell and Java. He asked me what Haskell's could do that Java's couldn't, and I realized that I didn't know. After thinking for a while, I came up with a very short list of minor differences. Not being heavy into type theory, I'm left wondering whether they're formally equivalent. To try and keep this from becoming a subjective question, I'm asking: what are the major, non-syntactical differences between their type systems? I realize some things are easier/harder in one than in the other, and I'm not interested in talking about those. And to make it more specific, let's ignore Haskell type extensions since there's so many out there that do all kinds of crazy/cool stuff.

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  • Type checking and recursive types (Writing the Y combinator in Haskell/Ocaml)

    - by beta
    When explaining the Y combinator in the context of Haskell, it's usually noted that the straight-forward implementation won't type-check in Haskell because of its recursive type. For example, from Rosettacode [1]: The obvious definition of the Y combinator in Haskell canot be used because it contains an infinite recursive type (a = a -> b). Defining a data type (Mu) allows this recursion to be broken. newtype Mu a = Roll { unroll :: Mu a -> a } fix :: (a -> a) -> a fix = \f -> (\x -> f (unroll x x)) $ Roll (\x -> f (unroll x x)) And indeed, the “obvious” definition does not type check: ?> let fix f g = (\x -> \a -> f (x x) a) (\x -> \a -> f (x x) a) g <interactive>:10:33: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 Expected type: t2 -> t0 -> t1 Actual type: (t2 -> t0 -> t1) -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a <interactive>:10:57: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a (0.01 secs, 1033328 bytes) The same limitation exists in Ocaml: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; Error: This expression has type 'a -> 'b but an expression was expected of type 'a The type variable 'a occurs inside 'a -> 'b However, in Ocaml, one can allow recursive types by passing in the -rectypes switch: -rectypes Allow arbitrary recursive types during type-checking. By default, only recursive types where the recursion goes through an object type are supported. By using -rectypes, everything works: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; val fix : (('a -> 'b) -> 'a -> 'b) -> 'a -> 'b = <fun> utop # let fact_improver partial n = if n = 0 then 1 else n*partial (n-1);; val fact_improver : (int -> int) -> int -> int = <fun> utop # (fix fact_improver) 5;; - : int = 120 Being curious about type systems and type inference, this raises some questions I'm still not able to answer. First, how does the type checker come up with the type t2 = t2 -> t0 -> t1? Having come up with that type, I guess the problem is that the type (t2) refers to itself on the right side? Second, and perhaps most interesting, what is the reason for the Haskell/Ocaml type systems to disallow this? I guess there is a good reason since Ocaml also will not allow it by default even if it can deal with recursive types if given the -rectypes switch. If these are really big topics, I'd appreciate pointers to relevant literature. [1] http://rosettacode.org/wiki/Y_combinator#Haskell

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  • How to solve 404 for static files with Django and Nginx?

    - by Lucio
    I setup a Trusty VM with Django + Nginx (other stuffs too). The server is working, I get the "Welcome to Django" page. But when I enter to servername/admin it loads the HTML page but fails to load the static content. And the admin page have this links to static content: <link rel="stylesheet" type="text/css" href="/static/admin/css/base.css" /> <link rel="stylesheet" type="text/css" href="/static/admin/css/login.css" /> Both of the CSS files give me 404, as the Nginx log shows: 192.168.56.1 - - [05/Jun/2014:12:04:09 -0300] "GET /admin HTTP/1.1" 301 5 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:29.0) Gecko/20100101 Firefox/29.0" 192.168.56.1 - - [05/Jun/2014:12:04:09 -0300] "GET /admin/ HTTP/1.1" 200 833 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:29.0) Gecko/20100101 Firefox/29.0" 192.168.56.1 - - [05/Jun/2014:12:04:10 -0300] "GET /static/admin/css/base.css HTTP/1.1" 404 142 "http://ubuntu-server/admin/" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:29.0) Gecko/20100101 Firefox/29.0" 192.168.56.1 - - [05/Jun/2014:12:04:10 -0300] "GET /static/admin/css/login.css HTTP/1.1" 404 142 "http://ubuntu-server/admin/" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:29.0) Gecko/20100101 Firefox/29.0" I think that the error is on my nginx.conf file, but do not know how to solve it.

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  • Types of semantic bugs, logic errors [closed]

    - by C-Otto
    I am a PhD student and currently focus on automatically finding instances of new types of bugs in (Java) programs that cannot be found by existing tools like FindBugs. The existing tool currently is used to prove/disprove termination of (Java) programs. I have some ideas (see below), but I could need more input from you (experienced programmers, potential users of my tool). What kind of bugs do you wish to find? What types of bugs exist and might be suitable for my analysis? One strength of the approach I use is detailled information about the heap. So in contrast to FindBugs, I can work with knowledge of the form "variable x and variable y are disjoint on the heap" or "variable z is not cyclic". It is also possible to see if a method might have side effects (and if so, which variables may/may not be affected by it). Example 1: Vacuous call: Graph graphOne = createGraph(); Graph graphTwo = createGraph(); Node source = graphTwo.getRootNode(); for (Node n : graphOne.getNodes()) { if (areConnected(source, n)) { graphTwo.addNode(n); } } Imagine createGraph() creates a fresh graph, so that graphOne and graphTwo are disjoint on the heap. Then, because source is taken from graphTwo instead of graphOne, the call to areConnected always returns false. In this situation I could find out that the call areConnected is useless (because it does not have any side effect and the return value always is false) which helps finding the real bug (taking source from the wrong graph). For this the information that x and y are disjoint (because graphOne and graphTwo are disjoint) is crucial. This bug is related to calling x.equals(y) where x and y are objects of different classes. In this scenario, most implementations of equals() always return false, which most likely is not the intended result. FindBugs already finds this bug (hardcoded to equals(), semantics of implementation is not checked). Example 2: Useless code: someCode(); while (something()) { yetMoreSomething(); } moreCode(); In the case that the loop (so the code in something() and yetMoreSomething()) does not modify anything visible outside the loop, it does not make sense to run this code - the program has the same behaviour as someCode(); moreCode() (i.e., without the loop). To find this out, one needs detailled information about the side effects of the (possibly useless) code. If I can prove that the code does not have any side effect that can be observed afterwards (in the example: in moreCode() or later), then the code indeed is useless. Of course, here Input/Output of any form must be seen as a side effect, so that a System.out.println(...) is not considered useless. Example 3: Ignored return value: Instead of x = foo(); and making use of x, the method is called without storing the result: foo();. If the method does not have any side effect, its invocation is useless and can be dropped. Most likely, the bug here is that the returned value should have been used. Here, too, detailled information about side effects are needed. Can you think of similar types of bugs that might be detected (only) with detailled information about the heap, side effects, semantics of called methods, ...? Did you encounter bugs related to the ones shown below in "real life"? By the way, the tool is AProVE and Java related publications can be found on my homepage. Thanks a lot, Carsten

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