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• What is the need of functional programming?

  - by Lazer

  I have read about functional programming which is stateless, gives the same result invocation after invocation, about closures and other related concepts. I still feel that I have very little idea what these things are about. Thinking about this, right now, I feel complete in C, C++, and Java. Any programming problem and I start thinking in one of these languages. So, I never feel and understand the need for functional languages. A good starting point therefore would be to try to understand some things that are not possible in imperative languages but possible in functional languages. I feel unless I understand where exactly functional languages fit inside my already complete world of C, C++ and Java, I would never be able to appreciate and understand them. So, can somebody help me understand the real need for functional programming? Where exactly do they fit in?

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• Hyper-V 2008 R2 synthetic networking stops working with linux 2.6.32.15

  - by luxifer

  Hi there, so I thought I'd give Hyper-V on Windows Server 2008 R2 Enterprise a try on my Homeserver (yes, it's legit... got it from msdnaa). First thing to throw at it was my firewall which runs IPFire. This distribution currently uses the kernel version 2.6.32.15 and comes with the Hyper-V drivers. So I enabled them and at first they work just fine but after a few minutes they just fail. There are no packages going in or out anymore until I reboot the VM but sometimes even that won't work so the VM just keeps "Stopping" like forever. Emulated networking works fine but it slow and uses more CPU. That way my firewall routes slower than when running under virtualbox on an atom N270. My server has an E6750; VM is limited to 25%, but that should still outperform this atom CPU especially since it's never going anywhere near 100% CPU load, so give me a break! A quick google search led me to people having the same problem (even with other distributions and kernel versions that include those drivers) but no solution yet... I already found this but I can't quite follow the author on the part where he solved the issue - especially since I need two virtual nics for my firewall distro to work (obviously one internal and one external) What am I missing here?

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• Centos 6.2 Fresh 'Basic Server' install networking issues

  - by RWC

  I've had a /29 provisioned on a network port for a server and am trying to at least configure the machine so I can ssh into it. It's Centos 6.2 x64 with the Basic Server install. Currently not able to ping gateway or any address for that matter. For reference: Default Interface: em2 Network ID: 66.*.*.0/29 Gateway: 66.*.*.1 Broadcast: 66.*.*.7 Please see my following configs: /etc/sysconfig/network-scripts/ifcfg-em2 DEVICE=em2 NM_CONTROLLED=yes ONBOOT=yes HWADDR=Not Important TYPE=Ethernet BOOTPROTO=none IPADDR=66.*.*.2 PREFIX=29 DNS1=8.8.8.8 DNS2=8.8.4.4 DEFROUTE=yes IPV4_FAILURE_FATAL=yes IPV6INIT=no NAME="System em2" NETMASK=255.255.255.248 USERCTL=no $: route -n Destination // Gateway // Genmask // Flags // Metric // Ref // Use // Iface 66.*.*.0 0.0.0.0 255.255.255.248 U 0 0 0 em2 169.254.0.0 0.0.0.0 255.255.0.0 U 0 1003 0 em2 0.0.0.0 66.*.*.1 0.0.0.0 UG 0 0 0 em2 $: route Destination // Gateway // Genmask // Flags // Metric // Ref // Use // Iface 66.*.*.0 * 255.255.255.248 U 0 0 0 em2 link-local * 255.255.0.0 U 0 1003 0 em2 default 66.*.*.1 0.0.0.0 UG 0 0 0 em2 $: cat /etc/sysconfig/network NETWORKING=yes HOSTNAME=excalibur.domain.com GATEWAY=66.*.*.1 Keep in mind that I cannot even currently ping the gateway which is quite confusing for me. My /etc/hosts are configured correctly with the *.2 address. I'm not concerned with getting all of the addresses on the /29 up and running yet, just one so I can at least ssh in. Thanks! Edit: Adding in ifconfig. $: ifconfig em2 Link encap:Ethernet HWaddr XX:XX:XX:XX:XX:XX inet addr:66.*.*.2 Bcat:66.*.*.7 Mask:255.255.255.248 inet6 addr: UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5536 errors:0 dropped:0 overruns:0 frame:0 TX packets:10 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2599469 (2.4 MiB) TX bytes: 748 (748.0 b) Interrupt:48 Memory:dc000000-dc012800 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:34 errors:0 etc etc

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• Networking - intermittent, slow speeds

  - by jack

  Hi all I'm a novice when it comes to networking. I live in a large two storey building that used to be a school and we have an internet connection with BT (british telecoms provider), the connection speed is 12Mb.. Basically our connection is slow and very intermittent and I was wondering if anybody here could provide some help or ideas. There are about 11 people in the building who could be online at any time. We have a router on the ground floor which is bog standard supplied by BT. To provide Broadband access to the 1st and 2nd floors, we used an old switch that the school left, we have a cable running from the router on the first floor to the switch which connects to a wireless router which is configured as a bridge on the 2nd floor supplying broadband access to the 1st and 2nd floors. Additionally we have 3 computers that are connected via the switch through the ethernet sockets left by the school on the ground floor. The router we use on the 2nd floor came in a pack of 2 and cost about £15 (bought by another person). Sometimes the connection is perfectly fine, i.e. early hours of the morning or when everybody is out, we have rang BT who say that the connection cannot cope with the numbers of people online, plus I'm not sure whether each person is streaming etc. Can anybody offer any advice?

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• CentOS networking BNX2

  - by james moore

  Having some trouble with my NICs. The server starts fine and I can wget/ping etc. However, when I /etc/init.d/networking restart I then receive the following error: Bringing up interface eth0: bnx2: fw sync timeout, reset code = 1030009 SIOCSIFFLAGS: Device or resource busy Consequently, the task fails. I have searched around on google users suggesting to disable PNP in the BIOS but I see no option. Here is some system information: $ ethtool -i eth0 driver: bnx2 version: 2.0.8-rh firmware-version: bc 2.9.1 $ uname -a Linux host 2.6.18-238.9.1.el5 #1 SMP Tue Apr 12 18:10:13 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux $/sbin/lspci | grep Broadcom 04:00.0 PCI brodge: Broadcom EPB PCI-Express to PCI-X Bridge (rev c3) 05:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5700 Gigabit Ethernet (rev 12) 08:00.0 PCI brodge: Broadcom EPB PCI-Express to PCI-X Bridge (rev c3) 09:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5700 Gigabit Ethernet (rev 12) $ lsmod | grep bnx2 bnx2i 81704 0 cnic 109512 1 bnx2i libiscsi2 77765 6 be2iscsi,ib_iser,iscsi_tcp,bnx2i,cxgb3i,libiscsi_tcp scsi_transport_iscsi2 73945 8 be2iscsi,ib_iser,iscsi_tcp,bnx2i,cxgb3i,libiscsi2 bnx2 224780 0 scsi_mod 199001 15 mpt2sas,scsi_transport_sas,mptctl,be2iscsi,ib_iser,iscsi_tcp,bnx2i,cxgb3i,libiscsi2,scsi_transport_iscsi2,scsi_dh,sg,libata,megaraid_sas,sd_mod $ rmmod bnx2; modprobe bnx2 PCI: Enabling device 0000:05:00.0 (0158 -> 015a) PCI: Enabling device 0000:09:00.0 (0158 -> 015a) bnx2: fw sync timeout, reset code = 10300003 Any help would be appreciated as I am at a loss.

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• Java Port Socket Programming Error

  - by atrus-darkstone

  Hi- I have been working on a java client-server program using port sockets. The goal of this program is for the client to take a screenshot of the machine it is running on, break the RGB info of this image down into integers and arrays, then send this info over to the server, where it is reconstructed into a new image file. However, when I run the program I am experiencing the following two bugs: The first number recieved by the server, no matter what its value is according to the client, is always 49. The client only sends(or the server only receives?) the first value, then the program hangs forever. Any ideas as to why this is happening, and what I can do to fix it? The code for both client and server is below. Thanks! CLIENT: import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.image.BufferedImage; import java.io.*; import java.net.Socket; import java.text.SimpleDateFormat; import java.util.*; import javax.swing.*; import javax.swing.Timer; public class ViewerClient implements ActionListener{ private Socket vSocket; private BufferedReader in; private PrintWriter out; private Robot robot; // static BufferedReader orders = null; public ViewerClient() throws Exception{ vSocket = null; in = null; out = null; robot = null; } public void setVSocket(Socket vs) { vSocket = vs; } public void setInput(BufferedReader i) { in = i; } public void setOutput(PrintWriter o) { out = o; } public void setRobot(Robot r) { robot = r; } /*************************************************/ public Socket getVSocket() { return vSocket; } public BufferedReader getInput() { return in; } public PrintWriter getOutput() { return out; } public Robot getRobot() { return robot; } public void run() throws Exception{ int speed = 2500; int pause = 5000; Timer timer = new Timer(speed, this); timer.setInitialDelay(pause); // System.out.println("CLIENT: Set up timer."); try { setVSocket(new Socket("Alex-PC", 4444)); setInput(new BufferedReader(new InputStreamReader(getVSocket().getInputStream()))); setOutput(new PrintWriter(getVSocket().getOutputStream(), true)); setRobot(new Robot()); // System.out.println("CLIENT: Established connection and IO ports."); // timer.start(); captureScreen(nameImage()); }catch(Exception e) { System.err.println(e); } } public void captureScreen(String fileName) throws Exception{ Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); Rectangle screenRectangle = new Rectangle(screenSize); BufferedImage image = getRobot().createScreenCapture(screenRectangle); int width = image.getWidth(); int height = image.getHeight(); int[] pixelData = new int[(width * height)]; image.getRGB(0,0, width, height, pixelData, width, height); byte[] imageData = new byte[(width * height)]; String fromServer = null; if((fromServer = getInput().readLine()).equals("READY")) { sendWidth(width); sendHeight(height); sendArrayLength((width * height)); sendImageInfo(fileName); sendImageData(imageData); } /* System.out.println(imageData.length); String fromServer = null; for(int i = 0; i < pixelData.length; i++) { imageData[i] = ((byte)pixelData[i]); } System.out.println("CLIENT: Pixel data successfully converted to byte data."); System.out.println("CLIENT: Waiting for ready message..."); if((fromServer = getInput().readLine()).equals("READY")) { System.out.println("CLIENT: Ready message recieved."); getOutput().println("SENDING ARRAY LENGTH..."); System.out.println("CLIENT: Sending array length..."); System.out.println("CLIENT: " + imageData.length); getOutput().println(imageData.length); System.out.println("CLIENT: Array length sent."); getOutput().println("SENDING IMAGE..."); System.out.println("CLIENT: Sending image data..."); for(int i = 0; i < imageData.length; i++) { getOutput().println(imageData[i]); } System.out.println("CLIENT: Image data sent."); getOutput().println("SENDING IMAGE WIDTH..."); System.out.println("CLIENT: Sending image width..."); getOutput().println(width); System.out.println("CLIENT: Image width sent."); getOutput().println("SENDING IMAGE HEIGHT..."); System.out.println("CLIENT: Sending image height..."); getOutput().println(height); System.out.println("CLIENT: Image height sent..."); getOutput().println("SENDING IMAGE INFO..."); System.out.println("CLIENT: Sending image info..."); getOutput().println(fileName); System.out.println("CLIENT: Image info sent."); getOutput().println("FINISHED."); System.out.println("Image data sent successfully."); } if((fromServer = getInput().readLine()).equals("CLOSE DOWN")) { getOutput().close(); getInput().close(); getVSocket().close(); } */ } public String nameImage() throws Exception { String dateFormat = "yyyy-MM-dd HH-mm-ss"; Calendar cal = Calendar.getInstance(); SimpleDateFormat sdf = new SimpleDateFormat(dateFormat); String fileName = sdf.format(cal.getTime()); return fileName; } public void sendArrayLength(int length) throws Exception { getOutput().println("SENDING ARRAY LENGTH..."); getOutput().println(length); } public void sendWidth(int width) throws Exception { getOutput().println("SENDING IMAGE WIDTH..."); getOutput().println(width); } public void sendHeight(int height) throws Exception { getOutput().println("SENDING IMAGE HEIGHT..."); getOutput().println(height); } public void sendImageData(byte[] imageData) throws Exception { getOutput().println("SENDING IMAGE..."); for(int i = 0; i < imageData.length; i++) { getOutput().println(imageData[i]); } } public void sendImageInfo(String info) throws Exception { getOutput().println("SENDING IMAGE INFO..."); getOutput().println(info); } public void actionPerformed(ActionEvent a){ String message = null; try { if((message = getInput().readLine()).equals("PROCESSING...")) { if((message = getInput().readLine()).equals("IMAGE RECIEVED SUCCESSFULLY.")) { captureScreen(nameImage()); } } }catch(Exception e) { JOptionPane.showMessageDialog(null, "Problem: " + e); } } } SERVER: import java.awt.image.BufferedImage; import java.io.*; import java.net.*; import javax.imageio.ImageIO; /*IMPORTANT TODO: * 1. CLOSE ALL STREAMS AND SOCKETS WITHIN CLIENT AND SERVER! * 2. PLACE MAIN EXEC CODE IN A TIMED WHILE LOOP TO SEND FILE EVERY X SECONDS * */ public class ViewerServer { private ServerSocket vServer; private Socket vClient; private PrintWriter out; private BufferedReader in; private byte[] imageData; private int width; private int height; private String imageInfo; private int[] rgbData; private boolean active; public ViewerServer() throws Exception{ vServer = null; vClient = null; out = null; in = null; imageData = null; width = 0; height = 0; imageInfo = null; rgbData = null; active = true; } public void setVServer(ServerSocket vs) { vServer = vs; } public void setVClient(Socket vc) { vClient = vc; } public void setOutput(PrintWriter o) { out = o; } public void setInput(BufferedReader i) { in = i; } public void setImageData(byte[] imDat) { imageData = imDat; } public void setWidth(int w) { width = w; } public void setHeight(int h) { height = h; } public void setImageInfo(String im) { imageInfo = im; } public void setRGBData(int[] rd) { rgbData = rd; } public void setActive(boolean a) { active = a; } /***********************************************/ public ServerSocket getVServer() { return vServer; } public Socket getVClient() { return vClient; } public PrintWriter getOutput() { return out; } public BufferedReader getInput() { return in; } public byte[] getImageData() { return imageData; } public int getWidth() { return width; } public int getHeight() { return height; } public String getImageInfo() { return imageInfo; } public int[] getRGBData() { return rgbData; } public boolean getActive() { return active; } public void run() throws Exception{ connect(); setActive(true); while(getActive()) { recieve(); } close(); } public void recieve() throws Exception{ String clientStatus = null; int clientData = 0; // System.out.println("SERVER: Sending ready message..."); getOutput().println("READY"); // System.out.println("SERVER: Ready message sent."); if((clientStatus = getInput().readLine()).equals("SENDING IMAGE WIDTH...")) { setWidth(getInput().read()); System.out.println("Width: " + getWidth()); } if((clientStatus = getInput().readLine()).equals("SENDING IMAGE HEIGHT...")) { setHeight(getInput().read()); System.out.println("Height: " + getHeight()); } if((clientStatus = getInput().readLine()).equals("SENDING ARRAY LENGTH...")) { clientData = getInput().read(); setImageData(new byte[clientData]); System.out.println("Array length: " + clientData); } if((clientStatus = getInput().readLine()).equals("SENDING IMAGE INFO...")) { setImageInfo(getInput().readLine()); System.out.println("Image Info: " + getImageInfo()); } if((clientStatus = getInput().readLine()).equals("SENDING IMAGE...")) { for(int i = 0; i < getImageData().length; i++) { getImageData()[i] = ((byte)getInput().read()); } } if((clientStatus = getInput().readLine()).equals("FINISHED.")) { getOutput().println("PROCESSING..."); setRGBData(new int[getImageData().length]); for(int i = 0; i < getRGBData().length; i++) { getRGBData()[i] = getImageData()[i]; } BufferedImage image = null; image.setRGB(0, 0, getWidth(), getHeight(), getRGBData(), getWidth(), getHeight()); ImageIO.write(image, "png", new File(imageInfo + ".png")); //create an image file out of the screenshot getOutput().println("IMAGE RECIEVED SUCCESSFULLY."); } } public void connect() throws Exception { setVServer(new ServerSocket(4444)); //establish server connection // System.out.println("SERVER: Connection established."); setVClient(getVServer().accept()); //accept client connection request // System.out.println("SERVER: Accepted connection request."); setOutput(new PrintWriter(vClient.getOutputStream(), true)); //set up an output channel setInput(new BufferedReader(new InputStreamReader(vClient.getInputStream()))); //set up an input channel // System.out.println("SERVER: Created IO ports."); } public void close() throws Exception { getOutput().close(); getInput().close(); getVClient().close(); getVServer().close(); } }

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• How to test my programming experience

  - by Oden

  Hey guys, I'm very excited about how experienced I am in programming. The first, working program that I have written, was in 2004 with C. Since this I have tried many programming languages, now got stuck with php. Currently I'm working as a web-developer, and everyones pleased with the work I do. Except me :) Thats the reason why i want to know, how high my experience and my knowledge is. Could you tell me, some tips, tricks, test, or anything, on what I can see how much I need to learn and practice to get a mastermind in programming? (at first place in php)

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• git networking for small team

  - by takeshin

  I'm trying to set up git for my programming team. My setup is: 1. example.com (Ubuntu server) IP: 192.168.1.2 (public: xxx.yyy.yyy.zzz) main git repository in /var/www/testgit user: mot (root) 2. host2, Ubuntu IP: 192.168.1.101 git clone of main repo in ~/public_html/testgit1 user: nairda 3. host3, Ubuntu IP: 192.168.1.102 git clone of main repo in ~/www/testgit2 user: mot 4. host4, Windows Vista, Samba, msysgit IP: 192.168.1.103 git clone of main repo in c:\shared\testgit3 user: ataga I start a new main repo: cd /var/www/testgit1 git init Now, a lot of questions: Which groups and users do I have to create? How to set up required ssh keys? (I'm playing with gitosis, but with no success by now.) How to make the main repo visible to other hosts? How to clone this repo on the hosts? How to pull changes from others to main repo?

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• KISS principle applied to programming language design?

  - by Giorgio

  KISS ("keep it simple stupid", see e.g. here) is an important principle in software development, even though it apparently originated in engineering. Citing from the wikipedia article: The principle is best exemplified by the story of Johnson handing a team of design engineers a handful of tools, with the challenge that the jet aircraft they were designing must be repairable by an average mechanic in the field under combat conditions with only these tools. Hence, the 'stupid' refers to the relationship between the way things break and the sophistication available to fix them. If I wanted to apply this to the field of software development I would replace "jet aircraft" with "piece of software", "average mechanic" with "average developer" and "under combat conditions" with "under the expected software development / maintenance conditions" (deadlines, time constraints, meetings / interruptions, available tools, and so on). So it is a commonly accepted idea that one should try to keep a piece of software simple stupid so that it easy to work on it later. But can the KISS principle be applied also to programming language design? Do you know of any programming languages that have been designed specifically with this principle in mind, i.e. to "allow an average programmer under average working conditions to write and maintain as much code as possible with the least cognitive effort"? If you cite any specific language it would be great if you could add a link to some document in which this intent is clearly expressed by the language designers. In any case, I would be interested to learn about the designers' (documented) intentions rather than your personal opinion about a particular programming language.

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• Functional programming compared to OOP with classes

  - by luckysmack

  I have been interested in some of the concepts of functional programming lately. I have used OOP for some time now. I can see how I would build a fairly complex app in OOP. Each object would know how to do things that object does. Or anything it's parents class does as well. So I can simply tell Person().speak() to make the person talk. But how do I do similar things in functional programming? I see how functions are first class items. But that function only does one specific thing. Would I simply have a say() method floating around and call it with an equivalent of Person() argument so I know what kind of thing is saying something? So I can see the simple things, just how would I do the comparable of OOP and objects in functional programming, so I can modularize and organize my code base? For reference, my primary experience with OOP is Python, PHP, and some C#. The languages that I am looking at that have functional features are Scala and Haskell. Though I am leaning towards Scala. Basic Example (Python): Animal(object): def say(self, what): print(what) Dog(Animal): def say(self, what): super().say('dog barks: {0}'.format(what)) Cat(Animal): def say(self, what): super().say('cat meows: {0}'.format(what)) dog = Dog() cat = Cat() dog.say('ruff') cat.say('purr')

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• First ATMs programming language

  - by revo

  First ATMs performed tasks like a cash dispenser, they were offline machines which worked with punch cards impregnated with Carbon and a 6-digit PIN code. Maximum withdrawal with a card was 10 pounds and each one was a one-time use card - ATM swallowed cards! The first ATM was installed in London in the year 1967, as I looked at time line of programming languages, there were many programming languages made before that decade. I don't know about the hardware neither, but in which programming language it was written? *I didn't find a detailed biography of John Shepherd-Barron (ATM inventor at 70s) Update I found this picture, which is taken from a newspaper back to the year 1972 in Iran. Translated PS : Shows Mr. Rad-lon (if spelled correctly), The manager of Barros (if spelled correctly) International Educational Institute in United Kingdom at the right, and Mr. Jim Sutherland - Expert of Computer Kiosks. In the rest of the text I found on this paper, these kind of ATMs which called "Automated Computer Kiosk" were advertised with this: Mr. Rad-lon (if spelled correctly) puts his card to one specific location of Automated Computer Kiosk and after 10 seconds he withdraws his cash. Two more questions are: 1- How those ATMs were so fast? (withdrawal in 10 seconds in that year) 2- I didn't find any text on Internet which state about "Automated Computer Kiosk", Is it valid or were they being called Computer in that time?

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• Pair Programming, for or against? [on hold]

  - by user1037729

  I believe it has many advantages over individual programming: Pros By pairing senior with relatively junior staff, the more junior can get up to speed with both project and computing experience, and the senior will re-think the problem in order to communicate with the junior, thus re-checking his own thinking (rubber duck principle!). At least 2 people will know about any single piece of work, if one person is away the other can cover, or if some one leaves a project knowledge transfer is easier. Two brains on a complex task is more effective, communication keeps the work free flowing and provides redundancy in decision making. Code is effectively reviewed as its being written, no need for a separate reviewing phase which requires a context switch as someone who has not been working on the piece in question would be required to understand and review the related code. Reviewing code on your own which you haven't written or architected is not fun, hence counter productive. Cons Less bandwith for performing tasks, lets say we have 4 devs, pair programming requires 2 devs per task, so we would be doing 2 tasks concurrently as a posed to 4. I believe this "Con" does not stand up as the pair programmed task would complete sooner and comes with a review built in for free! Ie the pair programming task would be more efficient and thus free up resources earlier. Less flexibility to chop and change tasks as two developers are tied into a task, when flexibility is required this could be a problem.

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• Networking issues with Linux server (CentOS 5.3)

  - by sxanness

  I have a Linux server hosting our bug tracking software (CentOS 5.2 Kernel 2.6.18-128.4.1.el5) that I have having some strange network problems with. The machine is configured with two NICS, one for the public interface and the other for our server back end network. The problem is that after doing a service network restart I can ping the public interface and it sends anywhere from 200-500 ICMP packets and then all of a sudden I start getting a request timed out error. Strange but as soon as I connect to the private interface the ping starts working again to the public interface. I clearly have a routing issue somewhere. I have a Juniper Router with the following configuration. Interface 0/0 -- Connect subnet to the ISP at our co-location Interface 0/2 -- For our DRAC network Interface 0/3 -- The Server-backend network (plugs directly into a switch that feeds to all the NICs that are on the 10.3.20.x network. Interface 0/4 -- Plugs directly into another switch that feeds our public interfaces, that interface as all the gateways from our public ip rangs as secondary IP addresses. I hope that someone can ask the right questions that can lead me to check things and figure out what is going on. Has anyone had similar problems and what kind of things should I be checking? Routing issue or something even more complicated? [root@fogbugz ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 # Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ DEVICE=eth0 BOOTPROTO=static IPADDR=72.249.134.98 NETMASK=255.255.255.248 BROADCAST=72.249.134.103 HWADDR=00:16:3E:AA:BB:EE ONBOOT=yes [root@fogbugz ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth1 # Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ DEVICE=eth1 BOOTPROTO=static BROADCAST=10.3.20.255 HWADDR=00:17:3E:AA:BB:EE IPADDR=10.3.20.25 NETMASK=255.255.255.0 NETWORK=10.3.20.0 ONBOOT=yes [root@fogbugz ~]# cat /etc/sysconfig/network NETWORKING=yes NETWORKING_IPV6=no HOSTNAME=fogbugz.dfw.hisg-it.net GATEWAY=72.249.134.97 [root@fogbugz ~]# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 72.249.134.96 0.0.0.0 255.255.255.248 U 0 0 0 eth0 10.3.20.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 10.0.0.0 10.3.20.1 255.0.0.0 UG 0 0 0 eth1 0.0.0.0 72.249.134.97 0.0.0.0 UG 0 0 0 eth0

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• Networking issues with Linux server (CentOS 5.3)

  - by sxanness

  I have a Linux server hosting our bug tracking software (CentOS 5.2 Kernel 2.6.18-128.4.1.el5) that I have having some strange network problems with. The machine is configured with two NICS, one for the public interface and the other for our server back end network. The problem is that after doing a service network restart I can ping the public interface and it sends anywhere from 200-500 ICMP packets and then all of a sudden I start getting a request timed out error. Strange but as soon as I connect to the private interface the ping starts working again to the public interface. I clearly have a routing issue somewhere. I have a Juniper Router with the following configuration. Interface 0/0 -- Connect subnet to the ISP at our co-location Interface 0/2 -- For our DRAC network Interface 0/3 -- The Server-backend network (plugs directly into a switch that feeds to all the NICs that are on the 10.3.20.x network. Interface 0/4 -- Plugs directly into another switch that feeds our public interfaces, that interface as all the gateways from our public ip rangs as secondary IP addresses. I hope that someone can ask the right questions that can lead me to check things and figure out what is going on. Has anyone had similar problems and what kind of things should I be checking? Routing issue or something even more complicated? [root@fogbugz ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 # Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ DEVICE=eth0 BOOTPROTO=static IPADDR=72.249.134.98 NETMASK=255.255.255.248 BROADCAST=72.249.134.103 HWADDR=00:16:3E:AA:BB:EE ONBOOT=yes [root@fogbugz ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth1 # Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ DEVICE=eth1 BOOTPROTO=static BROADCAST=10.3.20.255 HWADDR=00:17:3E:AA:BB:EE IPADDR=10.3.20.25 NETMASK=255.255.255.0 NETWORK=10.3.20.0 ONBOOT=yes [root@fogbugz ~]# cat /etc/sysconfig/network NETWORKING=yes NETWORKING_IPV6=no HOSTNAME=fogbugz.dfw.hisg-it.net GATEWAY=72.249.134.97 [root@fogbugz ~]# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 72.249.134.96 0.0.0.0 255.255.255.248 U 0 0 0 eth0 10.3.20.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 10.0.0.0 10.3.20.1 255.0.0.0 UG 0 0 0 eth1 0.0.0.0 72.249.134.97 0.0.0.0 UG 0 0 0 eth0

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• Wireless disabled after connecting ethernet cable

  - by user1716672

  Im using Linux Mint 13. Wireless has always worked fine but stopped yesterday after I connected to the internet via an ethernet cable. I ran: sudo rfkill list gives me: 0: phy0: Wireless LAN Soft blocked: yes Hard blocked: no sudo rfkill unblock 0 sudo rfkill list gives me 0: phy0: Wireless LAN Soft blocked: no Hard blocked: no sudo service networking start results in: networking stop/waiting The contents of /etc/network/interfaces is auto lo iface lo inet loopback Any ideas what I can do?

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• What resources do you recommend for learning more about TCP/IP, networking, and related areas?

  - by mkelley33

  As a relatively-new Python programmer, I'm finding more and more that networking as it relates to the web and web development is becoming increasingly important to understand. When I was an active C# ASP.NET programmer making smaller websites with less responsibility this knowledge seemed less important, since there was often a "networking" guy performing any tasks beyond acquiring a domain name for a client. Which books, websites, presentations, articles, or other resources would you recommend so that I best understand what's happening between the time a user types a URL and receives the rendered HTML? Thanks!

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• Tips on setting up a virtual lab for self-learning networking topics

  - by Harry

  I'm trying to self-learn the following topics on Linux (preferably Fedora): Network programming (using sockets API), especially across proxies and firewalls Proxies (of various kinds like transparent, http, socks...), Firewalls (iptables) and 'basic' Linux security SNAT, DNAT Network admininstration power tools: nc, socat (with all its options), ssh, openssl, etc etc. Now, I know that, ideally, it would be best if I had 'enough' number of physical nodes and physical network equipment (routers, switches, etc) for this self-learning exercise. But, obviously, don't have the budget or the physical space, nor want to be wasteful -- especially, when things could perhaps be simulated/emulated in a Linux environment. I have got one personal workstation, which is a single-homed Fedora desktop with 4GB memory, 200+ GB disk, and a 4-core CPU. I may be able to get 3 to 4 additional low-end Fedora workstations. But all of these -- including mine -- will always remain strictly behind our corporate firewall :-( Now, I know I could use VirtualBox-based virtual nodes, but don't know if there are any better alternatives disk- and memory- footprint-wise. Would you be able to give me some tips or suggestions on how to get started setting up this little budget- and space-constrained 'virtual lab' of mine? For example, how would I create virtual routers? Has someone attempted this sort of thing before: namely, creating a virtual network lab behind a corporate firewall for learning/development/testing purposes? I hope my question is not vague or too open-ended. Basically, right now, I don't know how to best leverage the Linux environment and the various 'goodies' it comes with, and buying physical devices only when it is absolutely necessary.

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• Parallel programming patterns for C#?

  - by VoidDweller

  With Intel's launch of a Hexa-Core processor for the desktop, it looks like we can no longer wait for Microsoft to make many-core programming "easy". I just order a copy of Joe Duffy's book Concurrent Programming on Windows. This looks like a great place to start, though, I am hoping some of you who have been targeting multi/many core systems would point me to some good resources that have or would have helped on your projects?

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• debian lenny xen bridge networking problem

  - by Sasha

  DomU isn't talking to the world, but it talks to Dom0. Here are the tests that I made: Dom0 (external networking is working): ping 188.40.96.238 #Which is Domu's ip PING 188.40.96.238 (188.40.96.238) 56(84) bytes of data. 64 bytes from 188.40.96.238: icmp_seq=1 ttl=64 time=0.092 ms DomU: ping 188.40.96.215 #Which is Dom0's ip PING 188.40.96.215 (188.40.96.215) 56(84) bytes of data. 64 bytes from 188.40.96.215: icmp_seq=1 ttl=64 time=0.045 ms ping 188.40.96.193 #Which is the gateway - fail PING 188.40.96.193 (188.40.96.193) 56(84) bytes of data. ^C --- 188.40.96.193 ping statistics --- 2 packets transmitted, 0 received, 100% packet loss, time 1013ms The system is debian lenny with a normal setup. Here is my configs: uname -a Linux green0 2.6.26-2-xen-686 #1 SMP Wed Aug 19 08:47:57 UTC 2009 i686 GNU/Linux cat /etc/xen/green1.cfg |grep -v '#' kernel = '/boot/vmlinuz-2.6.26-2-xen-686' ramdisk = '/boot/initrd.img-2.6.26-2-xen-686' memory = '2000' root = '/dev/xvda2 ro' disk = [ 'file:/home/xen/domains/green1/swap.img,xvda1,w', 'file:/home/xen/domains/green1/disk.img,xvda2,w', ] name = 'green1' vif = [ 'ip=188.40.96.238,mac=00:16:3E:1F:C4:CC' ] on_poweroff = 'destroy' on_reboot = 'restart' on_crash = 'restart' ifconfig eth0 Link encap:Ethernet HWaddr 00:24:21:ef:2f:86 inet addr:188.40.96.215 Bcast:188.40.96.255 Mask:255.255.255.192 inet6 addr: fe80::224:21ff:feef:2f86/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:3296 errors:0 dropped:0 overruns:0 frame:0 TX packets:2204 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:262717 (256.5 KiB) TX bytes:330465 (322.7 KiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) peth0 Link encap:Ethernet HWaddr 00:24:21:ef:2f:86 inet6 addr: fe80::224:21ff:feef:2f86/64 Scope:Link UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1 RX packets:3407 errors:0 dropped:657431448 overruns:0 frame:0 TX packets:2291 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:319941 (312.4 KiB) TX bytes:338423 (330.4 KiB) Interrupt:16 Base address:0x8000 vif2.0 Link encap:Ethernet HWaddr fe:ff:ff:ff:ff:ff inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1 RX packets:27 errors:0 dropped:0 overruns:0 frame:0 TX packets:151 errors:0 dropped:33 overruns:0 carrier:0 collisions:0 txqueuelen:32 RX bytes:1164 (1.1 KiB) TX bytes:20974 (20.4 KiB) ip a s 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: peth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000 link/ether 00:24:21:ef:2f:86 brd ff:ff:ff:ff:ff:ff inet6 fe80::224:21ff:feef:2f86/64 scope link valid_lft forever preferred_lft forever 4: vif0.0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff 5: veth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff 6: vif0.1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff 7: veth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff 8: vif0.2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff 9: veth2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff 10: vif0.3: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff 11: veth3: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff 12: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN link/ether 00:24:21:ef:2f:86 brd ff:ff:ff:ff:ff:ff inet 188.40.96.215/26 brd 188.40.96.255 scope global eth0 inet6 fe80::224:21ff:feef:2f86/64 scope link valid_lft forever preferred_lft forever 14: vif2.0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 32 link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff inet6 fe80::fcff:ffff:feff:ffff/64 scope link valid_lft forever preferred_lft forever brctl show bridge name bridge id STP enabled interfaces eth0 8000.002421ef2f86 no peth0 vif2.0 ip r l Dom0: 188.40.96.192/26 dev eth0 proto kernel scope link src 188.40.96.215 default via 188.40.96.193 dev eth0 DomU: 188.40.96.192/26 dev eth0 proto kernel scope link src 188.40.96.238 default via 188.40.96.193 dev eth0

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• Can aptitude for learning Programming paradigms be influenced by culture or native language's gramma

  - by DVK

  It is well known that different people have different aptitudes regarding various programming paradigms (e.g. some people have trouble learning non-procedural, especially functional languages. Some people have trouble understanding pointers - see Joel Spolsky's blog for musings on that. Some people have trouble grasping recursion). I was recently reading about a study that looked at how the grammar of someone's native language affected their speed of learning math. Can't find that article now but a quick googling found this reference. That led me to wondering whether someone's native culture or first language might affect their aptitude towards various programming paradigms. I'm more curious about positive influences - e.g. some trait that make it easier/faster for someone to learn a particular paradigm, for example native language grammar being very recursion-oriented. To be clear, I'm looking for how culture/language grammare may affect the difference between aptitude of the same person towards various paradigms as opposed to how it affects overall aptitude towards programming between different persons. Important: the only answers I'm interested in are either references to scientific studies, or personal observations from someone intimately familiar with a particular culture/language, including from their own experience. E.g. I'm not interested in your opinion of how Chinese being your first language affects anything unless you speak Chinese or worked with extremely large set of Chinese-native programmers extensively. I'm OK with your guesstimates not based on scientific studies, but please be sure to supply your reasoning about plausible causes of your observation. I'm not interested in culture-bashing (any such commends will be deleted or flagged for deletion). I'm also not particularly interested in culture-building - we all know Linus is from Finland and Tetris was written in Russia and Larry Wall is an American. Any culture/nation can produce a brilliant mind in any discipline. I'm interested in averages.

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• Programming languages, positional languages and natural languages

  - by Vitalij Zadneprovskij

  Some programming languages are modeled on machine code, like assembly languages. Other languages are modeled on a natural language, the English language. Others are not modeled on either machine code or natural language. Languages such as PROLOG, for example, don't follow either model. I came across this Perl module Lingua::Romana::Perligata, that allows to write programs using a syntax that is very similar to Latin. Are there programming languages that have less positional syntax? Are there other languages or modules that allow you to write in syntaxes inspired by other natural languages, like French, Hebrew or Farsi? There is a very long list on Wikipedia, but most of those projects are dead. There is a related question on StackOverflow. The answer that was accepted is "Use Google".

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• Confusion on networking service start/stop in Ubuntu

  - by Daniel Ball

  I'm preparing to move and took down two of my servers, leaving only one with some essential services running. What I neglected to consider was that one was the DHCP server(which I realized when somebody contacted me saying they couldn't connect. Whups). So because I only have a few hosts on this small network, I opted to just statically configure them for now. One of these is a new Ubuntu 11.04 server, where I have very little experience. I edited /etc/network/interfaces and /etc/hosts to reflect my changes. I ran $sudo /etc/init.d/networking stop *deconfiguring network interfaces ... So yay. Then I try to start, it gives me the mumbo jumbo about using services (why didn't it do that for the stop?) So instead I run ... $sudo service networking start networking stop/waiting Now, to me that says the status of the service is stopped. But when I ping another computer, I get a successful reply. So is it not actually stopped? More importantly, am I doing something wrong? Edit daniel@FOOBAR:~$ sudo service networking status networking stop/waiting daniel@FOOBAR:~$ sudo service networking stop stop: Unknown instance: daniel@FOOBAR:~$ sudo service networking status networking stop/waiting daniel@FOOBAR:~$ sudo service networking start networking stop/waiting daniel@FOOBAR:~$ sudo service networking status networking stop/waiting So you can see why I ran /etc/init.d/networking stop instead. For some reason upstart (that is what "services" is, right?) isn't working with stop. cat /etc/hosts 127.0.0.1 localhost 127.0.1.1 FOOBAR 198.3.9.2 FOOBAR #Added entry July 19 2011 # The following lines are desirable for IPv6 capable hosts ::1 ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters cat /etc/network/interfaces # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface #auto eth0 #iface eth0 inet dhcp # hostname FOOBAR auto eth0 iface eth0 inet static address 198.3.9.2 netmask 255.255.255.0 network 198.3.9.0 broadcast 198.3.9.255 gateway 198.3.9.15 No I didn't save backups, it was just a minor change so I just commented out the old DHCP setting. Edit I set everything back to original settings and set up a DHCP server. "starting" networking does the same thing. I can only assume this is normal, I just don't know WHY. It can't be anything to do with the configuration files, since they've been restored.

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• Visual Programming paradigms

  - by Rego

  As the number of "visual" OS's such as Android, iOS and the promised Windows 8 are becoming more popular, it does not seem to me that we programmers have new ways to code using these new technologies, due to a possible lack in new visual programming languages paradigms. I've seen several discussions about incompatibilities between the current coding development environment, and the new OS approaches from Windows 8, Android and other tablets OS's. I mean, today if we have a new tablet, it's almost a requirement for coding, to have, for instance, an external keyboard (due it seems to me it's very difficult to program using the touch screen), exactly because the coding assistance is not conceived to "write" thousands of lines of code. So, how advanced should be the "new" visual programming languages paradigms? Which characteristics these new paradigms would be required?

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• To maximize chances of functional programming employment

  - by Rob Agar

  Given that the future of programming is functional, at some point in the nearish future I want to be paid to code in a functional language, preferably Haskell. Assuming I have a firm grasp of the language, plus all the basic programmer attributes (good communication skills/sense of humour/hygiene etc), what should I concentrate on learning to maximize my chances? Are there any particularly sought after libraries I should know? Alternatively, would another language be a better bet, say F#? (I'm not too fussed about the kind of programming work, so long as it's reasonably interesting and reasonably well paid, and with nice people)

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• Design patterns and multiple programming language

  - by Eduard Florinescu

  I am referring here to the design patterns found in the GOF book. First how I see it, there are a few peculiarities to design pattern and knowing multiple language knowledge, for example in Java you really need a singleton but in Python you can do without it you write a module, I saw somewhere a wiki trying to write all GOF patterns for JavaScript and the entries where empty, I guess because it might be a daunting task. If there is someone who is using design patterns and is programming in multiple programming languages supporting the OOP paradigm and can give me a hint on how should I approach design patterns that might help me in all languages I use(Java, JavaScript, Python, Ruby): Can I write good application without knowing exactly the GOF design patterns or I might need some of them which might be crucial and if yes which one, are they alternatives to GOF for specific languages, and should a programmer or a team make its own design patterns set?

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