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  • mySQL Efficiency Issue - How to find the right balance of normalization...?

    - by Foo
    I'm fairly new to working with relational databases, but have read a few books and know the basics of good design. I'm facing a design decision, and I'm not sure how to continue. Here's a very over simplified version of what I'm building: People can rate photos 1-5, and I need to display the average votes on the picture while keeping track of the individual votes. For example, 12 people voted 1, 7 people voted 2, etc. etc. The normalization freak of me initially designed the table structure like this: Table pictures id* | picture | userID | Table ratings id* | pictureID | userID | rating With all the foreign key constraints and everything set as they shoudl be. Every time someone rates a picture, I just insert a new record into ratings and be done with it. To find the average rating of a picture, I'd just run something like this: SELECT AVG(rating) FROM ratings WHERE pictureID = '5' GROUP by pictureID Having it setup this way lets me run my fancy statistics to. I can easily find who rated a certain picture a 3, and what not. Now I'm thinking if there's a crapload of ratings (which is very possible in what I'm really designing), finding the average will became very expensive and painful. Using a non-normalized version would seem to be more efficient. e.g.: Table picture id | picture | userID | ratingOne | ratingTwo | ratingThree | ratingFour | ratingFive To calculate the average, I'd just have to select a single row. It seems so much more efficient, but so much more uglier. Can someone point me in the right direction of what to do? My initial research shows that I have to "find the right balance", but how do I go about finding that balance? Any articles or additional reading information would be appreciated as well. Thanks.

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  • Modeling software for network serialization protocol design

    - by Aurélien Vallée
    Hello, I am currently designing a low level network serialization protocol (in fact, a refinement of an existing protocol). As the work progress, pen and paper documents start to show their limits: i have tons of papers, new and outdated merged together, etc... And i can't show anything to anyone since i describe the protocol using my own notation (a mix of flow chart & C structures). I need a software that would help me to design a network protocol. I should be able to create structures, fields, their sizes, their layout, etc... and the software would generate some nice UMLish diagrams.

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  • How do I improve the efficiency of the queries executed by this generic Linq-to-SQL data access clas

    - by Lee D
    Hi all, I have a class which provides generic access to LINQ to SQL entities, for example: class LinqProvider<T> //where T is a L2S entity class { DataContext context; public virtual IEnumerable<T> GetAll() { return context.GetTable<T>(); } public virtual T Single(Func<T, bool> condition) { return context.GetTable<T>().SingleOrDefault(condition); } } From the front end, both of these methods appear to work as you would expect. However, when I run a trace in SQL profiler, the Single method is executing what amounts to a SELECT * FROM [Table], and then returning the single entity that meets the given condition. Obviously this is inefficient, and is being caused by GetTable() returning all rows. My question is, how do I get the query executed by the Single() method to take the form SELECT * FROM [Table] WHERE [condition], rather than selecting all rows then filtering out all but one? Is it possible in this context? Any help appreciated, Lee

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  • How to acces File over the Network

    - by Polo
    Hi! I am having a hard time on this one, I have à folder over the network wit public accès (no credential restriction). I am trying to do à File.Exist or Directory.Exist and I keep on having a exception. Can somewone tell me the good way to do IO over the network. EDIT 1 FOR DETAILS: if i do execture = \agoodip\Public\test.txt I get the file etc etc In my code it look like a basic Directory.Exist(@"\agoodip\Public") or File.exist(@"\agoodip\Public\test.txt") The exception I get is Path not found. Thanks!

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  • Creating a local CDMA or GSM network?

    - by Jeffrey Sambells
    I am developing a number of different mobile applications for a number of different mobile devices and I want to quickly test in a local development environment. I was wondering if it is possible (with some sort of hardware) to set up a local desktop CDMA / GSM base station for testing devices over a local personal cellular network. The range does not have to be very far. The alternative is purchasing a SIM card and plans for various carriers but not all carriers/network types are available in our area. I'm sure I had seen some sort of desktop device that would let you setup local networks for development/testing purposes but can't seem to find it. Thanks.

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  • C# Network Printing

    - by tanthiamhuat
    I am able to get the list of network printers via this code: private void Form1_Load(object sender, EventArgs e) { foreach (String printer in PrinterSettings.InstalledPrinters) { listBox1.Items.Add(printer.ToString()); } } For each network printer, I want to extract out more information like: (a) get document information, like number of pages printed, filename, file-size, etc. (b) get computer IP address from which document was printed. (c) get username of who printed the document. How do I achieve the above? any code samples would be appreciated. Do I have to look into Windows Management Instrumentation(WMI) stuffs?

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  • streaming to correct network interface

    - by robin hood
    I have IP cam that supports RTSP streaming. It's connected to router with 2 network cards with IP1 and IP2 addresses. I make 2 connections to IP cam by IP1 and IP2 addresses from the same IP and I need to receive corresponding streams thru correct network card, but both streams (RTP over UDP) go thru IP1. How this can be resolved? I don't know if RTSP server binds UDP sockets to corresponding IP and I don't know what IP stack is in IP cam (weak end system or strong end system). I haven't found anything interesting in router configuration. As I understand, routing table cannot help me cos I'm connected from the same IP, is it right? Also Sorry for incomplete info but it's all I have at the moment. Thanks for your time.

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  • Network Communication program in python

    - by lamnep
    Hi all, Basically what I'm trying to achieve is a program which allow users to connect to a each other over a network in, essentially, a chat room. What I'm currently struggling with is writing the code so that the users can connect to each other without knowing the IP-address of the computer that the other users are using or knowing the IP-address of a server. Does anyone know of a way in which I could simply have all of the users scan the IP range of my network in order to find any active 'room' and then give the user a chance to connect to it? Also, the hope is that there will be no need for a central server to run this from, rather every user will simply be connected to all other user, essentially being the server and client at the same time.

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  • Game network physics collision

    - by Jonas Byström
    How to simulating two client-controlled vehicles colliding (sensibly) in a typical client/server setup for a network game? I did read this eminent blog post on how to do distributed network physics in general (without traditional client prediction), but this question is specifically on how to handle collisions of owned objects. Example Say client A is 20 ms ahead of server, client B 300 ms ahead of server (counting both latency and maximum jitter). This means that when the two vehicles collide, both clients will see the other as 320 ms behind - in the opposite direction of the velocity of the other vehicle. Head-to-head on a Swedish highway means a difference of 16 meters/17.5 yards! What not to try It is virtually impossible to extrapolate the positions, since I also have very complex vehicles with joints and bodies all over, which in turn have linear and angular positions, velocities and accelerations, not to mention states from user input.

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  • Make network changes permanent - C++

    - by pparescasellas
    I need to allow an external client to change the IP of the Linux machine where the program is running (C++). I already know how to list all the local interfaces and the current IPs assigned to them. I also know how to programatically change said IPs. What I need to know is how to make this change permanent so, if the machine reboots, it keeps the same network configuration. What's the best way to do this? Manually parsing /etc/network/interfaces? Calling some linux command? Edit: I'm using Debian. Thanks!

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  • How to make sysctl network bridge settings persist after a reboot?

    - by Zack Perry
    I am setting up a notebook for software demo purpose. The machine has 8GB RAM, a Core i7 Intel CPU, a 128GB SSD, and runs Ubuntu 12.04 LTS 64bit. The notebook is used as a KVM host and runs a few KVM guests. All such guests use the virbr0 default bridge. To enable them to communicate with each other using multicast, I added the following to the host's /etc/sysctl.conf, as shown below net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 Afterwards, following man sysctl(8), I issued the following: sudo /sbin/sysctl -p /etc/sysctl.conf My understanding is that this should make these settings persist over reboots. I tested it, and was surprised to find out the following: root@sdn1 :/proc/sys/net/bridge# more *tables :::::::::::::: bridge-nf-call-arptables :::::::::::::: 1 :::::::::::::: bridge-nf-call-ip6tables :::::::::::::: 1 :::::::::::::: bridge-nf-call-iptables :::::::::::::: 1 All defaults are coming back! Yes. I can use some kludgy "get arounds" such as putting a /sbin/sysctl -p /etc/sysctl.conf into the host's /etc/rc.local but I would rather "do it right". Did I misunderstand the man page or is there something that I missed? Thanks for any hints. -- Zack

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  • Network Access: I can't access 192.168.1.101 from 192.168.1.102.

    - by takpar
    Hi, I'm running Ubuntu 10.04 on my PC with IP 192.168.1.101. every thing work fine, e.g. my web server is running and I can see http://localhost/ or http://192.168.1.101 properly. But the problem is that I cannot see my PC from my laptop at 192.168.1.102 e.g. at my laptop http://192.168.1.101 gives Connection timed out in browser. or trying to telnet on any port leads to: telnet: Unable to connect to remote host: Connection timed out laptop is running a fresh install of Ubuntu as well and there is no setup for firewall stuff in both computers. PS: Both computers can ping each other well. The router is a cicso linksys wireless ADSL modem. Currently, I can connect to FTP server on the Windows running on 192.168.1.102 from 192.168.1.101 without problem. Theses are commands ran on my PC, 192.168.1.101: ifconfig: adp@adp-desktop:~$ ifconfig eth0 Link encap:Ethernet HWaddr 00:26:18:e1:8e:cf inet addr:192.168.1.101 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe70::226:18ff:fee1:8ecf/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1831935 errors:0 dropped:0 overruns:0 frame:0 TX packets:1493786 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1996855925 (1.9 GB) TX bytes:215288238 (215.2 MB) Interrupt:27 Base address:0xa000 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:951742 errors:0 dropped:0 overruns:0 frame:0 TX packets:951742 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:494351095 (494.3 MB) TX bytes:494351095 (494.3 MB) vmnet1 Link encap:Ethernet HWaddr 00:50:46:c0:00:01 inet addr:192.168.91.1 Bcast:192.168.91.255 Mask:255.255.255.0 inet6 addr: fe70::250:56ff:fec0:1/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:50 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) vmnet8 Link encap:Ethernet HWaddr 00:50:46:c0:00:08 inet addr:192.168.156.1 Bcast:192.168.156.255 Mask:255.255.255.0 inet6 addr: fe70::250:56ff:fec0:8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:51 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) port 80 is set to 0.0.0.0 well: adp@adp-desktop:~$ netstat -ln | grep 'LISTEN ' tcp 0 0 127.0.0.1:52815 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4559 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4369 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:7634 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5269 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5280 0.0.0.0:* LISTEN tcp 0 0 127.0.1.1:7777 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:33601 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5222 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN tcp6 0 0 :::139 :::* LISTEN tcp6 0 0 ::1:631 :::* LISTEN tcp6 0 0 :::445 :::* LISTEN /etc/hosts.deny is empty: adp@adp-desktop:~$ cat /etc/hosts.deny # /etc/hosts.deny: list of hosts that are _not_ allowed to access the system. # See the manual pages hosts_access(5) and hosts_options(5). # # Example: ALL: some.host.name, .some.domain # ALL EXCEPT in.fingerd: other.host.name, .other.domain # # If you're going to protect the portmapper use the name "portmap" for the # daemon name. Remember that you can only use the keyword "ALL" and IP # addresses (NOT host or domain names) for the portmapper, as well as for # rpc.mountd (the NFS mount daemon). See portmap(8) and rpc.mountd(8) # for further information. # # The PARANOID wildcard matches any host whose name does not match its # address. # # You may wish to enable this to ensure any programs that don't # validate looked up hostnames still leave understandable logs. In past # versions of Debian this has been the default. # ALL: PARANOID netstat -l: adp@adp-desktop:~$ netstat -l Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 localhost:52815 *:* LISTEN tcp 0 0 *:hylafax *:* LISTEN tcp 0 0 *:www *:* LISTEN tcp 0 0 *:4369 *:* LISTEN tcp 0 0 localhost:7634 *:* LISTEN tcp 0 0 *:ftp *:* LISTEN tcp 0 0 *:xmpp-server *:* LISTEN tcp 0 0 localhost:ipp *:* LISTEN tcp 0 0 *:smtp *:* LISTEN tcp 0 0 *:5280 *:* LISTEN tcp 0 0 adp-desktop:7777 *:* LISTEN tcp 0 0 *:33601 *:* LISTEN tcp 0 0 *:xmpp-client *:* LISTEN tcp 0 0 localhost:mysql *:* LISTEN tcp6 0 0 [::]:netbios-ssn [::]:* LISTEN tcp6 0 0 localhost:ipp [::]:* LISTEN tcp6 0 0 [::]:microsoft-ds [::]:* LISTEN udp 0 0 *:bootpc *:* udp 0 0 *:mdns *:* udp 0 0 *:47467 *:* udp 0 0 192.168.1.10:netbios-ns *:* udp 0 0 192.168.91.1:netbios-ns *:* udp 0 0 192.168.156.:netbios-ns *:* udp 0 0 *:netbios-ns *:* udp 0 0 192.168.1.1:netbios-dgm *:* udp 0 0 192.168.91.:netbios-dgm *:* udp 0 0 192.168.156:netbios-dgm *:* udp 0 0 *:netbios-dgm *:* raw 0 0 *:icmp *:* 7 netstat -rn: adp@adp-desktop:~$ netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.91.0 0.0.0.0 255.255.255.0 U 0 0 0 vmnet1 192.168.156.0 0.0.0.0 255.255.255.0 U 0 0 0 vmnet8 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0 commands on the laptop, 192.168.1.102: ifconfig: root@fakeuser-laptop:~# ifconfig eth0 Link encap:Ethernet HWaddr 00:1c:33:a2:31:15 UP BROADCAST RUNNING MULTICAST MTU:1500 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:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:21 eth1 Link encap:Ethernet HWaddr 00:2d:d9:3e:1f:6c inet addr:192.168.1.102 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe70::21d:d9ff:fe3e:1f6c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5681 errors:0 dropped:0 overruns:0 frame:10313 TX packets:6717 errors:6 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:4055251 (4.0 MB) TX bytes:779308 (779.3 KB) Interrupt:18 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:206 errors:0 dropped:0 overruns:0 frame:0 TX packets:206 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:15172 (15.1 KB) TX bytes:15172 (15.1 KB) netstat -rn: root@fakeuser-laptop:~# netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 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 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth1

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  • How do I get wireless to work on a Dell Mini 1018 with Realtek RTL 8188CE Network Adapter?

    - by Laurence Nagel
    My Dell Mini 1018 used to work fine with Ubuntu 12.04 with no problems connecting with the wireless card. Then I made the big mistake of attempting to disable WiFi by right-clicking on the wireless applet and un-checking "Enable Wireless." Since then, I cannot get wireless working again. The wireless applet reports that "wireless is disabled by hardware switch" but there is no hardware switch on this computer. Issuing a rfkill list yields the following: 0: dell-wifi: Wireless LAN Soft blocked: yes Hard block: yes 1: phy0: Wireless LAN Soft blocked: no Hard blocked: yes I'm in way over my head, and my computer is now useless. Help!!!

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  • How migrate my keyring (containing ssh passprases, nautilus remote filesystem, pgp passwords) and network manager connections?

    - by con-f-use
    I changed the disk on my laptop and installed Ubuntu on the new disk. Old disk had 12.04 upgraded to 12.10 on it. Now I want to copy my old keyring with WiFi passwords, ftp passwords for nautilus and ssh key passphrases. I have the whole data from the old disk available (is now a USB disk and I did not delete the old data yet or do anything with it - I could still put it in the laptop and boot from it like nothing happened). On the new disc that is now in my laptop, I have installed 12.10 with the same password, user-id and username as on the old disk. Then I copied a few important config files from the old disk (e.g. ~/.firefox/, ~/.mozilla, ~/.skype and so on, which all worked fine... except for the key ring: The old methods of just copying ~/.gconf/... and ~/.gnome2/keyrings won't work. Did I miss something? 1. Edit: I figure one needs to copy files not located in the users home directory as well. I copied the whole old /home/confus (which is my home directory) to the fresh install to no effect. That whole copy is now reverted to the fresh install's home directory, so my /home/confus is as it was the after fresh install. 2. Edit: The folder /etc/NetworkManager/system-connections seems to be the place for WiFi passwords. Could be that /usr/share/keyrings is important as well for ssh keys - that's the only sensible thing that a search came up with: find /usr/ -name "*keyring* 3. Edit: Still no ssh and ftp passwords from the keyring. What I did: Convert old hard drive to usb drive Put new drive in the laptop and installed fresh version of 12.10 there (same uid, username and passwort) Booted from old hdd via USB and copied its /etc/NetwrokManager/system-connections, ~/.gconf/ and ~/.gnome2/keyrings, ~/.ssh over to the new disk. Confirmed that all keys on the old install work Booted from new disk Result: No passphrase for ssh keys, no ftp passwords in keyring. At least the WiFi passwords are migrated. 4. Edit: Boutny! Ending soon... 5. Edit: Keyring's now in ./local/share/keyrings/. Also interesting .gnupg

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  • Network connection fails when downloading data

    - by Guus
    In the past few weeks, I've noticed my network connection becoming unstable while downloading files. I'm not sure how to diagnose this issue. I've found that my network connections appear to be temporarily unresponsive (for periods up to a minute or so) while I'm downloading a file (that's large enough to not be downloaded instantly). The problem occurs when downloading data through a webbrowser, but also when using SCP to download data from a remote location. During the period in which network connections are unresponsive, every resource that I try to access over the network is unavailable. This includes: The download itself (SCP reports a 'stalled' download) Web pages (won't load - browsers report 'resource unavailable') SSH sessions (CLI freezes) VPN connections (connections terminate) IM client connections (client starts reconnection attempts) ... (everything is pretty much dead) I've noticed that during such a period, I cannot even access the (web-based) administrative console of the router on my LAN at home (although it remains reachable for other devices). The problem occurs when connected to my home network, but also when I'm in the office. Other devices than my laptop are not affected. Given the above two characteristics I assume the problem cause lies within my laptop, not the network infrastructure. I'm running Ubuntu 11.10. Apart from applying automatic updates from Ubuntu, I can't think of a change that I applied to the OS that could have started the problems. I'm absolutely positive that this issue did not occur up to a few weeks ago (as it's very noticeable, and only started to annoy me in the last few days). When the problem occurs, applications that make use of a network connection fail visibly (I get popups telling me that a VPN connection is broken, for instance). The network manager does not report any issues related to my wifi-connection though. Help?

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  • NetworkManager detects no networks with a RTL8188CE

    - by Cormac O'Brien
    I'm on a 2011 Lenovo Thinkpad T420i with a Realtek RTL8188CE WiFi adapter. Here's the scenario: I pop in the Ubuntu LiveCD to install. Laptop detects all networks in range, I connect to my home network, internet working great. Once Ubuntu finishes installing, the home network I am connected to is the only one which appears in the applet list. Upon restarting or waking from suspend, NetworkManager does not detect any networks – it simply displays "Disconnected" under the Wireless Network section of the menu. I am able to connect to my home network by using the "Connect to Hidden Wireless Network" option and it works immediately. I have yet to test if this works with other SSIDs. I have tried reinstalling the entire OS as well as NetworkManager and my wireless drivers. For hardware info, I ran: cormac@cormac-T420:~$ sudo lshw -c network Here is the output for my wireless card: *-network description: Wireless interface product: RTL8188CE 802.11b/g/n WiFi Adapter vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:03:00.0 logical name: wlan0 version: 01 serial: d0:df:9a:08:73:50 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=rtl8192ce driverversion=3.2.0-26-generic firmware=N/A ip=192.168.1.138 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn resources: irq:17 ioport:5000(size=256) memory:f2500000-f2503fff I can provide more information if required. This was not a problem in Natty or Oneiric. I hope this can be fixed, I don't want to have to ask for an SSID wherever I need to connect.

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  • Artificially create a connection timeout error

    - by Mark Ingram
    I've had a bug in our software that occurs when I receive a connection timeout. These errors are very rare (usually when my connection gets dropped by our internal network). How can I generate this kind of effect artificially so I can test our software? If it matters the app is written in C++/MFC using CAsyncSocket classes. Edit: I've tried using a non-existant host, and I get the socket error: WSAEINVAL (10022) Invalid argument My next attempt was to use Alexander's suggestion of connecting to a different port, e.g. 81 (on my own server though). That worked great. Exactly the same as a dropped connection (60 second wait, then error). Thank you!

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  • Capture IP packets on Dialup connection - Windows 7

    - by Assaf Levy
    Our product utilizes (the wonderful) Winpcap to capture ip packets from all devices with an IP address and analyze them in real time. Unfortunately, we discovered that it does NOT capture any packets on dialup (e.g. PPP) connections on Windows 7, and that there are no near-term plans for enabling this (1). So we need something else. Microsoft Network Monitor and Windows Packet Filter are two options that surfaced during a bit of googling, but before delving into research I wanted to ask the experienced: what are out options, given the following requirements: Capture all in/outbound IP packets on the machine. Complete background processing - no UI should be involved. Support Windows Vista / 7. Performance (user should not feel the difference). Thanks in advance.

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  • how to detect datacard connect and disconnect event on win32

    - by Vinayaka Karjigi
    Hi All, I have a data card, as soon as i insert the data card, i am getting the events by using wm_device_change event. But I also want to get event, when my data connect actually connects to out side world. I mean to say, as soon as we click on connect/disconnect button of data card,i want to get the event. exactly speaking wanted to know, when connection is established and disconnected. data card is vodaphone data card and i am trying to browse using that data card. what ever is the SDK, somewhere the OS should get the event of connection and disconnection to network is there any way to access that event which OS is getting. as i can see in notificaiton the changes of vodaphone connection and LAN connection data card is a USB device having SIM within it, and can be used to access internet through GPRS. can i know how to do this in win32 c/c++ programe. with regards Vinayaka Karjigi

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  • Performance considerations for common SQL queries

    - by Jim Giercyk
    Originally posted on: http://geekswithblogs.net/NibblesAndBits/archive/2013/10/16/performance-considerations-for-common-sql-queries.aspxSQL offers many different methods to produce the same results.  There is a never-ending debate between SQL developers as to the “best way” or the “most efficient way” to render a result set.  Sometimes these disputes even come to blows….well, I am a lover, not a fighter, so I decided to collect some data that will prove which way is the best and most efficient.  For the queries below, I downloaded the test database from SQLSkills:  http://www.sqlskills.com/sql-server-resources/sql-server-demos/.  There isn’t a lot of data, but enough to prove my point: dbo.member has 10,000 records, and dbo.payment has 15,554.  Our result set contains 6,706 records. The following queries produce an identical result set; the result set contains aggregate payment information for each member who has made more than 1 payment from the dbo.payment table and the first and last name of the member from the dbo.member table.   /*************/ /* Sub Query  */ /*************/ SELECT  a.[Member Number] ,         m.lastname ,         m.firstname ,         a.[Number Of Payments] ,         a.[Average Payment] ,         a.[Total Paid] FROM    ( SELECT    member_no 'Member Number' ,                     AVG(payment_amt) 'Average Payment' ,                     SUM(payment_amt) 'Total Paid' ,                     COUNT(Payment_No) 'Number Of Payments'           FROM      dbo.payment           GROUP BY  member_no           HAVING    COUNT(Payment_No) > 1         ) a         JOIN dbo.member m ON a.[Member Number] = m.member_no         /***************/ /* Cross Apply  */ /***************/ SELECT  ca.[Member Number] ,         m.lastname ,         m.firstname ,         ca.[Number Of Payments] ,         ca.[Average Payment] ,         ca.[Total Paid] FROM    dbo.member m         CROSS APPLY ( SELECT    member_no 'Member Number' ,                                 AVG(payment_amt) 'Average Payment' ,                                 SUM(payment_amt) 'Total Paid' ,                                 COUNT(Payment_No) 'Number Of Payments'                       FROM      dbo.payment                       WHERE     member_no = m.member_no                       GROUP BY  member_no                       HAVING    COUNT(Payment_No) > 1                     ) ca /********/                    /* CTEs  */ /********/ ; WITH    Payments           AS ( SELECT   member_no 'Member Number' ,                         AVG(payment_amt) 'Average Payment' ,                         SUM(payment_amt) 'Total Paid' ,                         COUNT(Payment_No) 'Number Of Payments'                FROM     dbo.payment                GROUP BY member_no                HAVING   COUNT(Payment_No) > 1              ),         MemberInfo           AS ( SELECT   p.[Member Number] ,                         m.lastname ,                         m.firstname ,                         p.[Number Of Payments] ,                         p.[Average Payment] ,                         p.[Total Paid]                FROM     dbo.member m                         JOIN Payments p ON m.member_no = p.[Member Number]              )     SELECT  *     FROM    MemberInfo /************************/ /* SELECT with Grouping   */ /************************/ SELECT  p.member_no 'Member Number' ,         m.lastname ,         m.firstname ,         COUNT(Payment_No) 'Number Of Payments' ,         AVG(payment_amt) 'Average Payment' ,         SUM(payment_amt) 'Total Paid' FROM    dbo.payment p         JOIN dbo.member m ON m.member_no = p.member_no GROUP BY p.member_no ,         m.lastname ,         m.firstname HAVING  COUNT(Payment_No) > 1   We can see what is going on in SQL’s brain by looking at the execution plan.  The Execution Plan will demonstrate which steps and in what order SQL executes those steps, and what percentage of batch time each query takes.  SO….if I execute all 4 of these queries in a single batch, I will get an idea of the relative time SQL takes to execute them, and how it renders the Execution Plan.  We can settle this once and for all.  Here is what SQL did with these queries:   Not only did the queries take the same amount of time to execute, SQL generated the same Execution Plan for each of them.  Everybody is right…..I guess we can all finally go to lunch together!  But wait a second, I may not be a fighter, but I AM an instigator.     Let’s see how a table variable stacks up.  Here is the code I executed: /********************/ /*  Table Variable  */ /********************/ DECLARE @AggregateTable TABLE     (       member_no INT ,       AveragePayment MONEY ,       TotalPaid MONEY ,       NumberOfPayments MONEY     ) INSERT  @AggregateTable         SELECT  member_no 'Member Number' ,                 AVG(payment_amt) 'Average Payment' ,                 SUM(payment_amt) 'Total Paid' ,                 COUNT(Payment_No) 'Number Of Payments'         FROM    dbo.payment         GROUP BY member_no         HAVING  COUNT(Payment_No) > 1   SELECT  at.member_no 'Member Number' ,         m.lastname ,         m.firstname ,         at.NumberOfPayments 'Number Of Payments' ,         at.AveragePayment 'Average Payment' ,         at.TotalPaid 'Total Paid' FROM    @AggregateTable at         JOIN dbo.member m ON m.member_no = at.member_no In the interest of keeping things in groupings of 4, I removed the last query from the previous batch and added the table variable query.  Here’s what I got:     Since we first insert into the table variable, then we read from it, the Execution Plan renders 2 steps.  BUT, the combination of the 2 steps is only 22% of the batch.  It is actually faster than the other methods even though it is treated as 2 separate queries in the Execution Plan.  The argument I often hear against Table Variables is that SQL only estimates 1 row for the table size in the Execution Plan.  While this is true, the estimate does not come in to play until you read from the table variable.  In this case, the table variable had 6,706 rows, but it still outperformed the other queries.  People argue that table variables should only be used for hash or lookup tables.  The fact is, you have control of what you put IN to the variable, so as long as you keep it within reason, these results suggest that a table variable is a viable alternative to sub-queries. If anyone does volume testing on this theory, I would be interested in the results.  My suspicion is that there is a breaking point where efficiency goes down the tubes immediately, and it would be interesting to see where the threshold is. Coding SQL is a matter of style.  If you’ve been around since they introduced DB2, you were probably taught a little differently than a recent computer science graduate.  If you have a company standard, I strongly recommend you follow it.    If you do not have a standard, generally speaking, there is no right or wrong answer when talking about the efficiency of these types of queries, and certainly no hard-and-fast rule.  Volume and infrastructure will dictate a lot when it comes to performance, so your results may vary in your environment.  Download the database and try it!

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  • Is case after case in a switch efficient?

    - by RandomGuy
    Just a random question regarding switch case efficiency in case after case; is the following code (assume pseudo code): function bool isValid(String myString){ switch(myString){ case "stringA": case "stringB": case "stringC": return true; default: return false; } more efficient than this: function bool isValid(String myString){ switch(myString){ case "stringA": return true; case "stringB": return true; case "stringC": return true; default: return false; } Or is the performance equal? I'm not thinking in a specific language but if needed let's assume it's Java or C (for this case would be needed to use chars instead of strings).

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