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• Quantifying the effects of partition mis-alignment

  - by Matt

  I'm experiencing some significant performance issues on an NFS server. I've been reading up a bit on partition alignment, and I think I have my partitions mis-aligned. I can't find anything that tells me how to actually quantify the effects of mis-aligned partitions. Some of the general information I found suggests the performance penalty can be quite high (upwards of 60%) and others say it's negligible. What I want to do is determine if partition alignment is a factor in this server's performance problems or not; and if so, to what degree? So I'll put my info out here, and hopefully the community can confirm if my partitions are indeed mis-aligned, and if so, help me put a number to what the performance cost is. Server is a Dell R510 with dual E5620 CPUs and 8 GB RAM. There are eight 15k 2.5” 600 GB drives (Seagate ST3600057SS) configured in hardware RAID-6 with a single hot spare. RAID controller is a Dell PERC H700 w/512MB cache (Linux sees this as a LSI MegaSAS 9260). OS is CentOS 5.6, home directory partition is ext3, with options “rw,data=journal,usrquota”. I have the HW RAID configured to present two virtual disks to the OS: /dev/sda for the OS (boot, root and swap partitions), and /dev/sdb for a big NFS share: [root@lnxutil1 ~]# parted -s /dev/sda unit s print Model: DELL PERC H700 (scsi) Disk /dev/sda: 134217599s Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 63s 465884s 465822s primary ext2 boot 2 465885s 134207009s 133741125s primary lvm [root@lnxutil1 ~]# parted -s /dev/sdb unit s print Model: DELL PERC H700 (scsi) Disk /dev/sdb: 5720768639s Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 34s 5720768606s 5720768573s lvm Edit 1 Using the cfq IO scheduler (default for CentOS 5.6): # cat /sys/block/sd{a,b}/queue/scheduler noop anticipatory deadline [cfq] noop anticipatory deadline [cfq] Chunk size is the same as strip size, right? If so, then 64kB: # /opt/MegaCli -LDInfo -Lall -aALL -NoLog Adapter #0 Number of Virtual Disks: 2 Virtual Disk: 0 (target id: 0) Name:os RAID Level: Primary-6, Secondary-0, RAID Level Qualifier-3 Size:65535MB State: Optimal Stripe Size: 64kB Number Of Drives:7 Span Depth:1 Default Cache Policy: WriteBack, ReadAdaptive, Direct, No Write Cache if Bad BBU Current Cache Policy: WriteThrough, ReadAdaptive, Direct, No Write Cache if Bad BBU Access Policy: Read/Write Disk Cache Policy: Disk's Default Number of Spans: 1 Span: 0 - Number of PDs: 7 ... physical disk info removed for brevity ... Virtual Disk: 1 (target id: 1) Name:share RAID Level: Primary-6, Secondary-0, RAID Level Qualifier-3 Size:2793344MB State: Optimal Stripe Size: 64kB Number Of Drives:7 Span Depth:1 Default Cache Policy: WriteBack, ReadAdaptive, Direct, No Write Cache if Bad BBU Current Cache Policy: WriteThrough, ReadAdaptive, Direct, No Write Cache if Bad BBU Access Policy: Read/Write Disk Cache Policy: Disk's Default Number of Spans: 1 Span: 0 - Number of PDs: 7 If it's not obvious, virtual disk 0 corresponds to /dev/sda, for the OS; virtual disk 1 is /dev/sdb (the exported home directory tree).

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• High I/O latency with software RAID, LUKS encrypted and LVM partitioned KVM setup

  - by aef

  I found out a performance problems with a Mumble server, which I described in a previous question are caused by an I/O latency problem of unknown origin. As I have no idea what is causing this and how to further debug it, I'm asking for your ideas on the topic. I'm running a Hetzner EX4S root server as KVM hypervisor. The server is running Debian Wheezy Beta 4 and KVM virtualisation is utilized through LibVirt. The server has two different 3TB hard drives as one of the hard drives was replaced after S.M.A.R.T. errors were reported. The first hard disk is a Seagate Barracuda XT ST33000651AS (512 bytes logical, 4096 bytes physical sector size), the other one a Seagate Barracuda 7200.14 (AF) ST3000DM001-9YN166 (512 bytes logical and physical sector size). There are two Linux software RAID1 devices. One for the unencrypted boot partition and one as container for the encrypted rest, using both hard drives. Inside the latter RAID device lies an AES encrypted LUKS container. Inside the LUKS container there is a LVM physical volume. The hypervisor's VFS is split on three logical volumes on the described LVM physical volume: one for /, one for /home and one for swap. Here is a diagram of the block device configuration stack: sda (Physical HDD) - md0 (RAID1) - md1 (RAID1) sdb (Physical HDD) - md0 (RAID1) - md1 (RAID1) md0 (Boot RAID) - ext4 (/boot) md1 (Data RAID) - LUKS container - LVM Physical volume - LVM volume hypervisor-root - LVM volume hypervisor-home - LVM volume hypervisor-swap - … (Virtual machine volumes) The guest systems (virtual machines) are mostly running Debian Wheezy Beta 4 too. We have one additional Ubuntu Precise instance. They get their block devices from the LVM physical volume, too. The volumes are accessed through Virtio drivers in native writethrough mode. The IO scheduler (elevator) on both the hypervisor and the guest system is set to deadline instead of the default cfs as that happened to be the most performant setup according to our bonnie++ test series. The I/O latency problem is experienced not only inside the guest systems but is also affecting services running on the hypervisor system itself. The setup seems complex, but I'm sure that not the basic structure causes the latency problems, as my previous server ran four years with almost the same basic setup, without any of the performance problems. On the old setup the following things were different: Debian Lenny was the OS for both hypervisor and almost all guests Xen software virtualisation (therefore no Virtio, also) no LibVirt management Different hard drives, each 1.5TB in size (one of them was a Seagate Barracuda 7200.11 ST31500341AS, the other one I can't tell anymore) We had no IPv6 connectivity Neither in the hypervisor nor in guests we had noticable I/O latency problems According the the datasheets, the current hard drives and the one of the old machine have an average latency of 4.12ms.

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• I am unable to run a client/server program in php

  - by sibi

  This is the program I am trying to run: $host = "127.0.0.1"; $port = 25003; // don't timeout! set_time_limit(0); // create socket $socket = socket_create(AF_INET, SOCK_STREAM, 0) or die("Could not create socket\n"); // bind socket to port $result = socket_bind($socket, $host, $port) or die("Could not bind to socket\n"); // start listening for connections $result = socket_listen($socket, 3) or die("Could not set up socket listener\n"); // accept incoming connections // spawn another socket to handle communication $spawn = socket_accept($socket) or die("Could not accept incoming connection\n"); // read client input $input = socket_read($spawn, 1024) or die("Could not read input\n"); // clean up input string $input = trim($input); echo "Client Message : ".$input; // reverse client input and send back $output = strrev($input) . "\n"; socket_write($spawn, $output, strlen ($output)) or die("Could not write output\n"); // close sockets socket_close($spawn); socket_close($socket); I enabled the PHP_socket option in WAMP but still I keep getting errors like unable to bind. Can someone please help me out?

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• Windows Phone 7 : Socket Programming

  - by davidhayes

  Is there any support for TCP/IP Sockets in Windows Phone 7? I'm not having any luck finding it so far. I want to connect to a port on a server and issue commands/receive responses

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• LDAP socket keep-alive

  - by Dmitry Khalatov

  We are using OpenLDAP client library to conect to an LDAP server. The problem is that if there is no activity for some time, server (or firewall in the middle) drops TCP connection. Our current implementation of "keep-alive" just does search for baseDN from time to time - any better ideas ?

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• socat usage for FIFO speed vs socket speed on localhost

  - by Fishy

  Hello, As per a suggestion on stackoverflow, to compare IPC on a single machine using a) sockets (TCP) on localhost to localhost b) using FIFOs (between Java and C) To answer (a), I used netcat to gauge transfer speed (91 MBytes/sec)[1] (b) Q: How can I test FIFO write speed using socat? My approach(where /tmp/gus is created using mkfifo on RHEL): dd if=/dev/zero of=/tmp/gus bs=1G count=1 but i get: 1073741824 bytes (1.1 GB) copied, 1.1326 seconds, 948 MB/s Does this mean writing to a FIFO ~10 times faster? Or is my experiment completely wrong ? Thank you Sporsi [1] From machine A to B across 1Gbps link, this number dropped to ~80 MBytes/sec - I expected localhost to be much higher ...

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• Using DockPanel Suite's XML saving with My.Settings

  - by Cyclone

  In vb.net, how can I use SaveAsXML and LoadFromXML (DockPanel Suite functions) with My.Settings? I know there is a way to save it to a stream, but I don't know enough about System.IO to do this. DockPanel Suite: http://sourceforge.net/projects/dockpanelsuite/ I would very much prefer to store configuration using My.Settings instead of as an XML file. Thanks for the help! EDIT: Since the only person to answer so far has since deleted their answer, I feel I should explain further: Those two methods can both accept a stream object, but I have not used System.IO enough to know how to properly initialize a stream, let alone get a string out of a stream. EDIT: Googling has gotten me nowhere. EDIT: Still waiting for this. I've tried everything...

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• Sending compressed data via socket

  - by Pizza

  Hi, I have to make a log server in java, and one task is to send the data compressed. Now I am sending it line by line in plain text, but I must compress it. The server handle "HTTP like" request. For example, I can get a log sending "GET xxx.log". This will entablish a TCP connection to the server, the server response with a header and the log, and close the connection. The client, reads line by line and analyzes each LOG entry. I tried some ways without success. My main problem is that I don't know where each line ends(in the client size). Any idea?

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• Java: Read POST data from a socket on an HTTP server

  - by danpalmer

  I have a website (python/django) that needs to use a load of Java resources that may or may not be on the same server. Therefore I am writing a mini webserver in Java that will receive a request and then when processing is finished, POST some data back to a url on the site. I have got the java code receiving connections on sockets and responding with some simple HTML. My problem is that I will POST data to the Java server and that code needs to act on the data. How do I go about reading the data that is posted in the HTML request, if it is even possible. If not, is there any other way you would do this. If you think I am going about this in completely the wrong way then please tell me and I will consider another method, but after conversing with some Java developers, this seemed like the best way for what I was doing. Thanks

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• Python 3 with the range function

  - by Leif Andersen

  I can type in the following code in the terminal, and it works: for i in range(5): print(i) And it will print: 0 1 2 3 4 as expected. However, I tried to write a script that does a similar thing: print(current_chunk.data) read_chunk(file, current_chunk) numVerts, numFaces, numEdges = current_chunk.data print(current_chunk.data) print(numVerts) for vertex in range(numVerts): print("Hello World") current_chunk.data is gained from the following method: def read_chunk(file, chunk): line = file.readline() while line.startswith('#'): line = file.readline() chunk.data = line.split() The output for this is: ['OFF'] ['490', '518', '0'] 490 Traceback (most recent call last): File "/home/leif/src/install/linux2/.blender/scripts/io/import_scene_off.py", line 88, in execute load_off(self.properties.path, context) File "/home/leif/src/install/linux2/.blender/scripts/io/import_scene_off.py", line 68, in load_off for vertex in range(numVerts): TypeError: 'str' object cannot be interpreted as an integer So, why isn't it spitting out Hello World 490 times? Or is the 490 being thought of as a string? I opened the file like this: def load_off(filename, context): file = open(filename, 'r')

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• ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)

  - by Imran

  Can someone please help as i've spent all day trying to fix this. I installed the latest XAMPP and now i can't connect to mysql from terminal.I checked my .profile file and the PATH seems ok. Does anyone know whats happened and what's the solution? PATH=$PATH:/Applications/XAMPP/xamppfiles/bin export PATH THIS IS A PROGRAMMING QUESTION AS I'M A PHP DEVELOPER TRYING TO DO MY JOB! Thankyou soo much in advance;-)

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• Need help manipulating WAV (RIFF) Files at a byte level

  - by Eric

  I'm writing an an application in C# that will record audio files (*.wav) and automatically tag and name them. Wave files are RIFF files (like AVI) which can contain meta data chunks in addition to the waveform data chunks. So now I'm trying to figure out how to read and write the RIFF meta data to and from recorded wave files. I'm using NAudio for recording the files, and asked on their forums as well on SO for way to read and write RIFF tags. While I received a number of good answers, none of the solutions allowed for reading and writing RIFF chunks as easily as I would like. But more importantly I have very little experience dealing with files at a byte level, and think this could be a good opportunity to learn. So now I want to try writing my own class(es) that can read in a RIFF file and allow meta data to be read, and written from the file. I've used streams in C#, but always with the entire stream at once. So now I'm little lost that I have to consider a file byte by byte. Specifically how would I go about removing or inserting bytes to and from the middle of a file? I've tried reading a file through a FileStream into a byte array (byte[]) as shown in the code below. System.IO.FileStream waveFileStream = System.IO.File.OpenRead(@"C:\sound.wav"); byte[] waveBytes = new byte[waveFileStream.Length]; waveFileStream.Read(waveBytes, 0, waveBytes.Length); And I could see through the Visual Studio debugger that the first four byte are the RIFF header of the file. But arrays are a pain to deal with when performing actions that change their size like inserting or removing values. So I was thinking I could then to the byte[] into a List like this. List<byte> list = waveBytes.ToList<byte>(); Which would make any manipulation of the file byte by byte a whole lot easier, but I'm worried I might be missing something like a class in the System.IO name-space that would make all this even easier. Am I on the right track, or is there a better way to do this? I should also mention that I'm not hugely concerned with performance, and would prefer not to deal with pointers or unsafe code blocks like this guy. If it helps at all here is a good article on the RIFF/WAV file format.

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• Socket programming C# vs C++

  - by klay

  Hi My company is willing to develop a server application, the application will use one port, clients will connect to this port and sending data every 3 minutes, casually the server will send some data. my questions are: how many connection can be handled when connecting to one port? which language Do we choose to write the Application (mainly between C# and C++)? (performance, ease of development) thanks

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• Problem reading hexadecimal buffer from C socket

  - by Olaseni

  I'm using the SDL_net sockets API to create a server and client. I can easily read a string buffer, but when I try to send hexadecimal data, recv gets the length, but I cannot seem to be a able to read the buffer contents. IPaddress ip; TCPsocket server,client; int bufSize = 1024; char message[bufSize]; int len; server = SDLNet_TCP_Open(&ip); client = SDLNet_TCP_Accept(server); len = SDLNet_TCP_Recv(client,message,bufSize); Here's a snippet. the buffer length "len" is set (i.e. message length) but I can't get to the data contents in the message buffer. Some sample bind_transmitter PDU data was sent by a random client to the server at that port. I can't read the PDU (SMPP).

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• What is node.js?

  - by Jeffrey

  I don't fully get what node.js is all about. Maybe it's because I am mainly a web based business app developer. Can someone please explain what it is and the use of it? Thanks. My understanding so far is that: The programming model is event driven, especially the way it handles IO. It uses javascript and the parser is V8. It can be easily used to create concurrent server apps. Are my understandings correct? If yes, then what are the benefits of evented IO, is it just more for the concurrency stuffs? Also is the direction of node.js to become a framework like, javascript based (v8 based) programming model?

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• Package management fails in update-manager with gzip problems and compilation errors. U12.04LTS

  - by HarveyP

  Similar to but not the same as Package management system corrupted. Cannot install or remove packages. U12.04LTS (an earlier problem) with package management system. Followed all of L. D. James suggestions in his answer to no avail. This time as well as the gzip error I am also getting compilation errors. The difference may be due to a lack of compilation in my earlier problem so it may be the same error. The packages concerned are enumerated in the output from update-manager below. Also included below that is the output from apt-get -f install apt-get autoremove gives same output. Tried update without SSL updates - 9 to install and got "Unhandled Error in aptdaemon". Output number 3 below. One at a time - output 4 - is for firefox, first in the list of packages. Falls over at libssl1.0.0 despite deselection of it from update ... Tried apt-get install --reinstall dpkg which succeeded, apt-get install --reinstall tar and apt-get install --reinstall gzip both of which failed at libssl1.0.0 as ever. (as suggested by Subv3rsion elsewhere in this forum) Now cannot apt-get update with complete success even after changing server and apt-get clean - output number 5 below ... 1). Output from update-manager The following packages will be upgraded:<> firefox firefox-globalmenu firefox-locale-en libavcodec-extra-53 libavformat53 libavutil-extra-51 libjson0 libpostproc52 libssl1.0.0 libswscale2 openssl 11 to upgrade, 0 to newly install, 0 to remove and 0 not to upgrade.<br> Need to get 0 B/46.5 MB of archives. After this operation, 1,416 kB of additional disk space will be used.<br> Do you want to continue [Y/n]? y debconf: Perl may be unconfigured (Bareword "gensym" not allowed while "strict subs" in use at /usr/lib/perl/5.14/IO/Handle.pm line 67. BEGIN not safe after errors--compilation aborted at /usr/lib/perl/5.14/IO/Handle.pm line 366. Compilation failed in require at /usr/lib/perl/5.14/IO/Seekable.pm line 9. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/Seekable.pm line 9. Compilation failed in require at /usr/lib/perl/5.14/IO/File.pm line 11. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/File.pm line 11. Compilation failed in require at /usr/share/perl/5.14/FileHandle.pm line 9. Compilation failed in require at (eval 1) line 3. BEGIN failed--compilation aborted at (eval 1) line 3. ) -- aborting (Reading database ... 160575 files and directories currently installed.) Preparing to replace libssl1.0.0 1.0.1-4ubuntu5.14 (using .../libssl1.0.0_1.0.1-4ubuntu5.15_i386.deb) ... Unpacking replacement libssl1.0.0 ... dpkg-deb (subprocess): data: internal gzip read error: '<fd:4>: data error' dpkg-deb: error: subprocess <decompress> returned error exit status 2 dpkg: error processing /var/cache/apt/archives/libssl1.0.0_1.0.1-4ubuntu5.15_i386.deb (--unpack):<br> subprocess dpkg-deb --fsys-tarfile returned error exit status 2 No apport report written because MaxReports has already been reached Bareword "gensym" not allowed while "strict subs" in use at /usr/lib/perl/5.14/IO/Handle.pm line 67. BEGIN not safe after errors--compilation aborted at /usr/lib/perl/5.14/IO/Handle.pm line 366. Compilation failed in require at /usr/lib/perl/5.14/IO/Seekable.pm line 9. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/Seekable.pm line 9. Compilation failed in require at /usr/lib/perl/5.14/IO/File.pm line 11. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/File.pm line 11. Compilation failed in require at /usr/share/perl/5.14/FileHandle.pm line 9. Compilation failed in require at /usr/share/perl5/Debconf/Template.pm line 8. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Template.pm line 8. Compilation failed in require at /usr/share/perl5/Debconf/Question.pm line 8. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Question.pm line 8. Compilation failed in require at /usr/share/perl5/Debconf/Config.pm line 7. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Config.pm line 7. Compilation failed in require at /usr/share/perl5/Debconf/Log.pm line 10. Compilation failed in require at /usr/share/perl5/Debconf/Db.pm line 7. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Db.pm line 7. Compilation failed in require at /usr/share/debconf/frontend line 6. BEGIN failed--compilation aborted at /usr/share/debconf/frontend line 6. dpkg: error whale cleanang up: subprgcess installed post-installation script returned error exit status 2 Errors were encountered while processing: /var/cache/apt/archives/libssl1.0.0_1.0.1-4ubuntu5.15_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1) 2). Output from install -f harveyp@harveyp:~$ sudo apt-get -f install [sudo] password for harveyp: Reading package lists... Done Building dependency tree Reading state information... Done 0 to upgrade, 0 to newly install, 0 to remove and 11 not to upgrade. 1 not fully installed or removed.<br> After this operation, 0 B of additional disk space will be used. E: Internal Error, No file name for libssl1.0.0 3). Unhandled error from aptdaemon Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1045, in _simulate trans.unauthenticated = self.__simulate(trans) File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1160, in __simulate unauthenticated = self._get_unauthenticated() File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 347, in _get_unauthenticated for pkg in self._iterate_packages(): File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1356, in _iterate_packages for enum, pkg in enumerate(self._cache): File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 216, in __iter__ yield self[pkgname] File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 201, in __getitem__ pkg = self._weakref[key] = Package(self, self._cache[key]) KeyError: 'librqrcode-rubq-doc 4). output from update of firefox installArchives() failed: Error in function: < Setting up libssl1.0.0 (1.0.1-4ubuntu5.14) ... Bareword "gensym" not allowed while "strict subs" in use at /usr/lib/perl/5.14/IO/Handle.pm line 67. BEGIN not safe after errors--compilation aborted at /usr/lib/perl/5.14/IO/Handle.pm line 366. Compilation failed in require at /usr/lib/perl/5.14/IO/Seekable.pm line 9. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/Seekable.pm line 9. Compilation failed in require at /usr/lib/perl/5.14/IO/File.pm line 11. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/File.pm line 11. Compilation failed in require at /usr/share/perl/5.14/FileHandle.pm line 9. Compilation failed in require at /usr/share/perl5/Debconf/Template.pm line 8. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Template.pm line 8. Compilation failed in require at /usr/share/perl5/Debconf/Question.pm line 8. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Question.pm line 8. Compilation failed in require at /usr/share/perl5/Debconf/Config.pm line 7. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Config.pm line 7. Compilation failed in require at /usr/share/perl5/Debconf/Log.pm line 10. 5. output from apt-get update ...snip ... Hit http://ubuntu-archive.mirrors.free.org precise-security/multiverse Translation-en Hit http://ubuntu-archive.mirrors.free.org precise-security/restricted Translation-en Hit http://ubuntu-archive.mirrors.free.org precise-security/universe Translation-en Fetched 368 kB in 6s (59.5 kB/s) W: Failed to fetch gzip:/var/lib/apt/lists/partial/ubuntu-archive.mirrors.free.org_ubuntu_dists_precise_universe_source_Sources Hash Sum mismatch E: Some index files failed to download. They have been ignored, or old ones used instead.

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• Mysterious socket / HttpWebRequest timeouts

  - by Daniel Mošmondor

  I have a great app for capturing shoutcast streams :-) . So far, it worked with a charm on dozens of machines, and never exhibited behaviour I found now, which is ultimately very strange. I use HttpWebRequest to connect to the shoutcast server and when I connect two streams, everything's OK. When I go for third one, response = (HttpWebResponse)request.GetResponse(); throws with Connection Timeout exception. WTF? I must point out that I had to create .config for the application in order to allow my headers to be sent out from the application, otherwise it wouldn't work at all. Here it is: <?xml version="1.0" encoding="utf-8" ?> <configuration> <system.net> <settings> <httpWebRequest useUnsafeHeaderParsing = "true" /> </settings> </system.net> </configuration> Does any of this ring a bell?

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• Java - Save video stream from Socket to File

  - by Alex

  I use my Android application for streaming video from phone camera to my PC Server and need to save them into file on HDD. So, file created and stream successfully saved, but the resulting file can not play with any video player (GOM, KMP, Windows Media Player, VLC etc.) - no picture, no sound, only playback errors. I tested my Android application into phone and may say that in this instance captured video successfully stored on phone SD card and after transfer it to PC played witout errors, so, my code is correct. In the end, I realized that the problem in the video container: data streamed from phone in MP4 format and stored in *.mp4 files on PC, and in this case, file may be incorrect for playback with video players. Can anyone suggest how to correctly save streaming video to a file? There is my code that process and store stream data (without errors handling to simplify): // getOutputMediaFile() returns a new File object DataInputStream in = new DataInputStream (server.getInputStream()); FileOutputStream videoFile = new FileOutputStream(getOutputMediaFile()); int len; byte buffer[] = new byte[8192]; while((len = in.read(buffer)) != -1) { videoFile.write(buffer, 0, len); } videoFile.close(); server.close(); Also, I would appreciate if someone will talk about the possible "pitfalls" in dealing with the conservation of media streams. Thank you, I hope for your help! Alex.

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• Epoll in EPOLLET mode returning 2 EPOLLIN before reading from the socket

  - by Arkaitz Jimenez

  The epoll manpage says that a fd registered with EPOLLET(edge triggered) shouldn't notify twice EPOLLIN if no read has been done. So after an EPOLLIN you need to empty the buffer before epoll_wait being able to return a new EPOLLIN on new data. However I'm experiencing problems with this approach as I'm seeing duplicated EPOLLIN events for untouched fds. This is the strace output, 0x200 is EPOLLRDHUP that is not defined yet in my glibc headers but defined in the kernel. 30285 epoll_ctl(3, EPOLL_CTL_ADD, 9, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP|EPOLLET|0x2000, {u32=9, u64=9}}) = 0 30285 epoll_wait(3, {{EPOLLIN, {u32=9, u64=9}}}, 10, -1) = 1 30285 epoll_wait(3, {{EPOLLIN, {u32=9, u64=9}}}, 10, -1) = 1 30285 epoll_wait(3, <unfinished ...> 30349 epoll_ctl(3, EPOLL_CTL_DEL, 9, NULL) = 0 30306 recv(9, "7u\0\0\10\345\241\312\t\20\f\32\r\10\27\20\2\30\200\10 \31(C0\17\32\r\10\27\20\2\30"..., 20000, 0) = 20000 30349 epoll_ctl(3, EPOLL_CTL_DEL, 9, NULL) = -1 ENOENT (No such file or directory) 30305 recv(9, " \31(C0\17\32\r\10\27\20\2\30\200\10 \31(C0\17\32\r\10\27\20\2\30\200\10 \31("..., 20000, 0) = 10011 So, after adding fd number 9 I do receive 2 consecutive EPOLLIN events before having recving the file descriptor, the syscall trace shows how I do delete the fd before reading but it should only happen once, one per event. So either I am not reading the manpage properly or something is now working here.

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• Php, socket and connecting to pop3-server

  - by Ockonal

  Hi guys, I'm trying to connect to the pop3-server with php. Here is my code: $pop3Server = 'mail.roller.ru'; $pop_conn = fsockopen($pop3Server, 110, $errno, $errstr, 10); print fgets($pop_conn, 1024); Warning: fsockopen() [function.fsockopen]: php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution in /home/ockonal/public_html/mail_parser.php on line 45 Warning: fsockopen() [function.fsockopen]: unable to connect to mail.roller.ru:110 (php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution) in /home/ockonal/public_html/mail_parser.php on line 45 Warning: fgets() expects parameter 1 to be resource, boolean given in /home/ockonal/public_html/mail_parser.php on line 46 What's wrong? I'm sure in pop3-server address. It doesn't print anything.

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• aio_write on linux with rtkaio is sometimes long

  - by Drakosha

  I'm using async io on linux with rtkaio library. In my tests everything works perfectly, but, in my real application i see that aio_write which is supposed to return very fast, is very slow. It can take more than 100 milis to write a 128KB to a O_DIRECT padded file. Both my test and the application use same I/O size, i check on the same file system (GFS). I added counting and i see that there are about 50% of async io operations that are short (shorter then 2 milis) and 50% that are long (longer than 2 milis). I also checked that the test and the application both use the same rtkaio library. I'm pretty lost, anyone any ideas where should i look? Another my related question: http://stackoverflow.com/questions/1799537/proc-sys-fs-aio-nr-is-never-higher-than-1024-aio-on-linux

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• python socket.recv/sendall call blocking

  - by fsm

  Hi everyone. This post is incorrectly tagged 'send' since I cannot create new tags. I have a very basic question about this simple echo server. Here are some code snippets. client while True: data = raw_input("Enter data: ") mySock.sendall(data) echoedData = mySock.recv(1024) if not echoedData: break print echoedData server while True: print "Waiting for connection" (clientSock, address) = serverSock.accept() print "Entering read loop" while True: print "Waiting for data" data = clientSock.recv(1024) if not data: break clientSock.send(data) clientSock.close() Now this works alright, except when the client sends an empty string (by hitting the return key in response to "enter data: "), in which case I see some deadlock-ish behavior. Now, what exactly happens when the user presses return on the client side? I can only imagine that the sendall call blocks waiting for some data to be added to the send buffer, causing the recv call to block in turn. What's going on here? Thanks for reading!

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• How to output binary data to a socket with Ruby

  - by Earlz

  Hello I have a very simple HTTP ruby server. I want it to simply server a PNG image. So I sent headers like image/png but I think that Ruby is converting the image data to a string first. Here is my relevant code webserver = TCPServer.new('127.0.0.1', 20001) while (session = webserver.accept) #.... file = File.open("tmp_testserve.png", "rb") contents = file.read file.close session.print @content session.close #.... Is this what is happening?

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• Android app unexpectedly quitted when I closed the bluetooth serversocket or bluetooth socket

  - by Lewisou

  The android app quitted without any warning and error when bluetoothServersocket.close() called in the main thread while bluetoothServersocket.accept(); was blocked for incoming connections in another thread. Here is pieces of my code. public void run() { try { bluetoothServerSocket = BluetoothAdapter. getDefaultAdapter().listenUsingRfcommWithServiceRecord(LISTEN_NAME, LISTEN_UUID); /* the thread blocked here for incoming connections */ bluetoothSocket = bluetoothServerSocket.accept(); ... } catch(Exception e) {} finally { try {bluetoothServerSocket.close();} catch(Exception ex) {} try {bluetoothSocket.close();} catch(Exception ex) {} } } And in the activity. public void onStop () { try{thread.bluetoothSocket.close();} catch(Exception ex) {} try{thread.bluetoothServerSocket.close();} catch(Exception ex) {} super.onStop(); } When I clicked the back button. The activity closed but after about one second the app quitted without any warning. My android os version is 2.2. a HTC Desire device.

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• Drawbacks with reading and writing a big file to or from disk at once instead of small chunks?

  - by Johann Gerell

  I work mainly on Windows and Windows CE based systems, where CreateFile, ReadFile and WriteFile are the work horses, no matter if I'm in native Win32 land or in managed .Net land. I have so far never had any obvious problem writing or reading big files in one chunk, as opposed to looping until several smaller chunks are processed. I usually delegate the IO work to a background thread that notifies me when it's done. But looking at file IO tutorials or "textbook examples", I often find the "loop with small chunks" used without any explanation of why it's used instead of the more obvious (I dare to say!) "do it all at once". Are there any drawbacks to the way I do that I haven't understood?

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