Search Results

Search found 1931 results on 78 pages for 'bsd sockets'.

Page 43/78 | < Previous Page | 39 40 41 42 43 44 45 46 47 48 49 50  | Next Page >

• flash socket policy

  - by WoppyCold

  Using flash sockets in my irc client, can I server the socket policy file somehow other than thru socket policy file server (without server)?

  Read the article

• How can I asynchronously monitor a file in Perl?

  - by Hussain

  I am wondering if it is possible, and if so how, one could create a perl script that constantly monitors a file/db, and then call a subroutine to perform text processing if the file is changed. I'm pretty sure this would be possible using sockets, but this needs to be used for a webchat application on a site running on a shared host, and I'm not so sure sockets would be allowed on it. The basic idea is: create a listener for a chat file/database when the file is updated with a new message, call a subroutine the called subroutine will send the new message back to the browser to be displayed Thanks in advance.

  Read the article

• Perl: Asynchronous file monitoring

  - by Hussain

  I am wondering if it is possible, and if so how, one could create a perl script that constantly monitors a file/db, and then call a subroutine to perform text processing if the file is changed. I'm pretty sure this would be possible using sockets, but this needs to be used for a webchat application on a site running on a shared host, and I'm not so sure sockets would be allowed on it. The basic idea is: -create a listener for a chat file/database -when the file is updated with a new message, call a subroutine -the called subroutine will send the new message back to the browser to be displayed Thanks in advance.

  Read the article

• Does TCP actually define 'TCP server' and 'TCP clients'? [closed]

  - by mjn

  In the Wikipedia article, TCP communication is explained using the terms 'client' and 'server'. It also uses the word 'peers'. But TCP actually does not define "TCP clients" and "TCP servers" - In the RFC 675 document (SPECIFICATION OF INTERNET TRANSMISSION CONTROL PROGRAM), the word "client" never appears. The RFC explains that TCP is used to connect processes over ports (sockets), and that 'A pair of sockets form a CONNECTION which can be used to carry data in either direction [i.e. full duplex]. Calling the originating party the "client" seems to be common practice. But this client/server communication model is not always applicable to TCP communication. For example take peer-to-peer networks. Calling all processes which open a socket (and wait for incoming connections from peers) "TCP servers", sounds wrong to me. I would not call my uncle's telephone device a "Telephony server" if I dial his phone number and he picks up.

  Read the article

• How can I communicate between Windows 8 and WP8 apps using ssl?

  - by Clay Shannon

  I'm considering using either raw notifications (WNS) or sockets for communication between a Windows 8 and WP8 app. I've found some samples for using sockets but my question[s] here are: does WP8 support sending/receiving messages over ssl and, if so, how is it done? Something I need to be true or find a workaround for is that the Windows 8 app has a permanent IPAddress to which the phone app will send its updates. Typically, a tablet will be running Windows 8 app, always listening for incoming messages; the phone app will periodically send messages.

  Read the article

• Autocad 2014 - Positioning electrical objects for plans (icons and symbols, not actual objects)

  - by zazkapulsk

  I am using Autocad to design my home. I am at a phase where I want to set the location for the switches, lighting fixtures, power sockets, communication sockets etc. I am thinking of something like this http://www.the-house-plans-guide.com/electrical-blueprint-symbols.html. I am not interested in placing specific lighting fixtures or rendering them, just putting the symbol and distances for the symbol. I can use Autocad Electrical, but that's a GIANT overshoot. What am I missing? Thanks.

  Read the article

• TDD, Unit Test and architectural changes

  - by Leandro

  I'm writing an RPC middleware in C++. I have a class named RPCClientProxy that contains a socket client inside: class RPCClientProxy { ... private: Socket* pSocket; ... } The constructor: RPCClientProxy::RPCClientProxy(host, port) { pSocket = new Socket(host, port); } As you can see, I don't need to tell the user that I have a socket inside. Although, to make unit tests for my proxies it would be necessary to create mocks for sockets and pass them to the proxies, and to do so I must use a setter or pass a factory to the sockets in the proxies's constructors. My question: According to TDD, is it acceptable to do it ONLY because the tests? As you can see, these changes would change the way the library is used by a programmer.

  Read the article

• Does a servlet-based stack have significant overheads?

  - by John

  I don't know if it's simply because page-loads take a little time, or the way servlets have an abstraction framework above the 'bare metal' of HTTP, or just because of the "Enterprise" in Jave-EE, but in my head I have the notion that a servlet-based app is inherently adding overhead compared to a Java app which simply deals with sockets directly. Forget web-pages, imagine instead a Java server app where you send it a question over an HTTP request and it looks up an answer from memory and returns the answer in the response. You can easily write a Java socket-based app which does this, you can also do a servlet approach and get away from the "bare metal" of sockets. Is there any measurable performance impact to be expected implementing the same approach using Servlets rather than a custom socket-based HTTP listening app? And yes, I am hazy on the exact data sent in HTTP requests and I know it's a vague question. It's really about whether servlet implementations have lots of layers of indirection or anything else that would add up to a significant overhead per call, where by significant I mean maybe an additional 0.1s or more.

  Read the article

• Any info about book "Unix Internals: The New Frontiers" by Uresh Vahalia 2nd edition (Jan 2010)

  - by claws

  This summer I'm getting into UNIX (mostly *BSD) development. I've graduate level knowledge about operating systems. I can also understand the code & read from here and there but the thing is I want to make most of my time. Reading books are best for this. From my search I found that these two books The Design and Implementation of the 4.4 BSD Operating System "Unix Internals: The New Frontiers" by Uresh Vahalia are like established books on UNIX OS internals. But the thing is these books are pretty much outdated. yay!! Lucky me. "Unix Internals: The New Frontiers" by Uresh Vahalia 2 edition (Jan 2010) is released. I've been search for information on this book. Sadly, Amazon says "Out of Print--Limited Availability" & I couldn't find any info regarding this book. This is the information I'm looking for: Table of Contents Whats new in this edition? Where the hell can I buy soft-copy of this book? I really cannot afford buying a hardcopy. How can I contact the author? I've lot of hopes & expectations on this book. I've been waiting for its release for a long time. I've sent random mails to & & requesting to have a proper website for this book. I even contacted publisher for any further information but no replies from any one. If you have any other books that you think will help me. I again repeat, I want to get max possible out of these 2.5 months summer.

  Read the article

• Micro Second resolution timestamps on windows.

  - by Nikhil

  How to get micro second resolution timestamps on windows? I am loking for something better than QueryPerformanceCounter, QueryPerformanceFrequency (these can only give you an elapsed time since boot, and are not necessarily accurate if they are called on different threads - ie QueryPerformanceCounter may return different results on different CPUs. There are also some processors that adjust their frequency for power saving, which apparently isn't always reflected in their QueryPerformanceFrequency result.) There is this, http://msdn.microsoft.com/en-us/magazine/cc163996.aspx but it does not seem to be solid. This looks great but its not available for download any more. http://www.ibm.com/developerworks/library/i-seconds/ This is another resource. http://www.lochan.org/2005/keith-cl/useful/win32time.html But requires a number of steps, running a helper program plus some init stuff also, I am not sure if it works on multiple CPUs Also looked at the Wikipedia link on the subject which is interesting but not that useful. http://en.wikipedia.org/wiki/Time_Stamp_Counter If the answer is just do this with BSD or Linux, its a lot easier thats fine, but I would like to confirm this and get some explanation as to why this is so hard in windows and so easy in linux and bsd. Its the same damm hardware...

  Read the article

• How to redirect http requests to https (nginx)

  - by spuder

  There appear to be many questions and guides out there that instruct how to setup nginx to redirect http requests to https. Many are outdated, or just flat out wrong. # MANAGED BY PUPPET upstream gitlab { server unix:/home/git/gitlab/tmp/sockets/gitlab.socket; } # setup server with or without https depending on gitlab::gitlab_ssl variable server { listen *:80; server_name gitlab.localdomain; server_tokens off; root /nowhere; rewrite ^ https://$server_name$request_uri permanent; } server { listen *:443 ssl default_server; server_name gitlab.localdomain; server_tokens off; root /home/git/gitlab/public; ssl on; ssl_certificate /etc/ssl/certs/ssl-cert-snakeoil.pem; ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key; ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2; ssl_ciphers AES:HIGH:!ADH:!MDF; ssl_prefer_server_ciphers on; # individual nginx logs for this gitlab vhost access_log /var/log/nginx/gitlab_access.log; error_log /var/log/nginx/gitlab_error.log; location / { # serve static files from defined root folder;. # @gitlab is a named location for the upstream fallback, see below try_files $uri $uri/index.html $uri.html @gitlab; } # if a file, which is not found in the root folder is requested, # then the proxy pass the request to the upsteam (gitlab puma) location @gitlab { proxy_read_timeout 300; # https://github.com/gitlabhq/gitlabhq/issues/694 proxy_connect_timeout 300; # https://github.com/gitlabhq/gitlabhq/issues/694 proxy_redirect off; proxy_set_header X-Forwarded-Proto $scheme; proxy_set_header X-Forwarded-Ssl on; proxy_set_header Host $http_host; proxy_set_header X-Real-IP $remote_addr; proxy_pass http://gitlab; } } I've restarted after every configuration change, and yet I still only get the 'Welcome to nginx' page when visiting http://192.168.33.10. whereas https://192.168.33.10 works perfectly. Why will nginx still not redirect http requests to https? I've also tried the following configurations listen *:80; server_name <%= @fqdn %>; #root /nowhere; #rewrite ^ https://$server_name$request_uri? permanent; #rewrite ^ https://$server_name$request_uri permanent; #return 301 https://$server_name$request_uri; #return 301 http://$server_name$request_uri; #return 301 http://192.168.33.10$request_uri; return 301 http://$host$request_uri; The logs tailf /var/log/nginx/access.log 192.168.33.1 - - [22/Oct/2013:03:41:39 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:24.0) Gecko/20100101 Firefox/24.0" 192.168.33.1 - - [22/Oct/2013:03:44:43 +0000] "GET / HTTP/1.1" 200 133 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:24.0) Gecko/20100101 Firefox/24.0" tailf /var/log/nginx/gitlab_error.lob 2013/10/22 02:29:14 [crit] 27226#0: *1 connect() to unix:/home/git/gitlab/tmp/sockets/gitlab.socket failed (2: No such file or directory) while connecting to upstream, client: 192.168.33.1, server: gitlab.localdomain, request: "GET / HTTP/1.1", upstream: "http://unix:/home/git/gitlab/tmp/sockets/gitlab.socket:/", host: "192.168.33.10" Resources http://wiki.nginx.org/Pitfalls How to make nginx redirect How to force or redirect to SSL in nginx? nginx ssl redirect Nginx & Https Redirection https://www.tinywp.in/301-redirect-wordpress/ How to force or redirect to SSL in nginx?

  Read the article

• Setting up an SSL Certificate in Apache

  When the HTTP protocol was designed, it was assumed that data transmission would be secure. Times have changed and network security has become much more important to us, especially for certain tasks. Sukrit Dhandhania shows you how to set up Secure Sockets Layer.

  Read the article

• WebSocket and Java EE 7 - Getting Ready for JSR 356 (TOTD #181)

  - by arungupta

  WebSocket is developed as part of HTML 5 specification and provides a bi-directional, full-duplex communication channel over a single TCP socket. It provides dramatic improvement over the traditional approaches of Polling, Long-Polling, and Streaming for two-way communication. There is no latency from establishing new TCP connections for each HTTP message. There is a WebSocket API and the WebSocket Protocol. The Protocol defines "handshake" and "framing". The handshake defines how a normal HTTP connection can be upgraded to a WebSocket connection. The framing defines wire format of the message. The design philosophy is to keep the framing minimum to avoid the overhead. Both text and binary data can be sent using the API. WebSocket may look like a competing technology to Server-Sent Events (SSE), but they are not. Here are the key differences: WebSocket can send and receive data from a client. A typical example of WebSocket is a two-player game or a chat application. Server-Sent Events can only push data data to the client. A typical example of SSE is stock ticker or news feed. With SSE, XMLHttpRequest can be used to send data to the server. For server-only updates, WebSockets has an extra overhead and programming can be unecessarily complex. SSE provides a simple and easy-to-use model that is much better suited. SSEs are sent over traditional HTTP and so no modification is required on the server-side. WebSocket require servers that understand the protocol. SSE have several features that are missing from WebSocket such as automatic reconnection, event IDs, and the ability to send arbitrary events. The client automatically tries to reconnect if the connection is closed. The default wait before trying to reconnect is 3 seconds and can be configured by including "retry: XXXX\n" header where XXXX is the milliseconds to wait before trying to reconnect. Event stream can include a unique event identifier. This allows the server to determine which events need to be fired to each client in case the connection is dropped in between. The data can span multiple lines and can be of any text format as long as EventSource message handler can process it. WebSockets provide true real-time updates, SSE can be configured to provide close to real-time by setting appropriate timeouts. OK, so all excited about WebSocket ? Want to convert your POJOs into WebSockets endpoint ? websocket-sdk and GlassFish 4.0 is here to help! The complete source code shown in this project can be downloaded here. On the server-side, the WebSocket SDK converts a POJO into a WebSocket endpoint using simple annotations. Here is how a WebSocket endpoint will look like: @WebSocket(path="/echo")public class EchoBean { @WebSocketMessage public String echo(String message) { return message + " (from your server)"; }} In this code "@WebSocket" is a class-level annotation that declares a POJO to accept WebSocket messages. The path at which the messages are accepted is specified in this annotation. "@WebSocketMessage" indicates the Java method that is invoked when the endpoint receives a message. This method implementation echoes the received message concatenated with an additional string. The client-side HTML page looks like <div style="text-align: center;"> <form action=""> <input onclick="send_echo()" value="Press me" type="button"> <input id="textID" name="message" value="Hello WebSocket!" type="text"><br> </form></div><div id="output"></div> WebSocket allows a full-duplex communication. So the client, a browser in this case, can send a message to a server, a WebSocket endpoint in this case. And the server can send a message to the client at the same time. This is unlike HTTP which follows a "request" followed by a "response". In this code, the "send_echo" method in the JavaScript is invoked on the button click. There is also a <div> placeholder to display the response from the WebSocket endpoint. The JavaScript looks like: <script language="javascript" type="text/javascript"> var wsUri = "ws://localhost:8080/websockets/echo"; var websocket = new WebSocket(wsUri); websocket.onopen = function(evt) { onOpen(evt) }; websocket.onmessage = function(evt) { onMessage(evt) }; websocket.onerror = function(evt) { onError(evt) }; function init() { output = document.getElementById("output"); } function send_echo() { websocket.send(textID.value); writeToScreen("SENT: " + textID.value); } function onOpen(evt) { writeToScreen("CONNECTED"); } function onMessage(evt) { writeToScreen("RECEIVED: " + evt.data); } function onError(evt) { writeToScreen('<span style="color: red;">ERROR:</span> ' + evt.data); } function writeToScreen(message) { var pre = document.createElement("p"); pre.style.wordWrap = "break-word"; pre.innerHTML = message; output.appendChild(pre); } window.addEventListener("load", init, false);</script> In this code The URI to connect to on the server side is of the format ws://<HOST>:<PORT>/websockets/<PATH> "ws" is a new URI scheme introduced by the WebSocket protocol. <PATH> is the path on the endpoint where the WebSocket messages are accepted. In our case, it is ws://localhost:8080/websockets/echo WEBSOCKET_SDK-1 will ensure that context root is included in the URI as well. WebSocket is created as a global object so that the connection is created only once. This object establishes a connection with the given host, port and the path at which the endpoint is listening. The WebSocket API defines several callbacks that can be registered on specific events. The "onopen", "onmessage", and "onerror" callbacks are registered in this case. The callbacks print a message on the browser indicating which one is called and additionally also prints the data sent/received. On the button click, the WebSocket object is used to transmit text data to the endpoint. Binary data can be sent as one blob or using buffering. The HTTP request headers sent for the WebSocket call are: GET ws://localhost:8080/websockets/echo HTTP/1.1Origin: http://localhost:8080Connection: UpgradeSec-WebSocket-Extensions: x-webkit-deflate-frameHost: localhost:8080Sec-WebSocket-Key: mDbnYkAUi0b5Rnal9/cMvQ==Upgrade: websocketSec-WebSocket-Version: 13 And the response headers received are Connection:UpgradeSec-WebSocket-Accept:q4nmgFl/lEtU2ocyKZ64dtQvx10=Upgrade:websocket(Challenge Response):00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 The headers are shown in Chrome as shown below: The complete source code shown in this project can be downloaded here. The builds from websocket-sdk are integrated in GlassFish 4.0 builds. Would you like to live on the bleeding edge ? Then follow the instructions below to check out the workspace and install the latest SDK: Check out the source code svn checkout https://svn.java.net/svn/websocket-sdk~source-code-repository Build and install the trunk in your local repository as: mvn install Copy "./bundles/websocket-osgi/target/websocket-osgi-0.3-SNAPSHOT.jar" to "glassfish3/glassfish/modules/websocket-osgi.jar" in your GlassFish 4 latest promoted build. Notice, you need to overwrite the JAR file. Anybody interested in building a cool application using WebSocket and get it running on GlassFish ? :-) This work will also feed into JSR 356 - Java API for WebSocket. On a lighter side, there seems to be less agreement on the name. Here are some of the options that are prevalent: WebSocket (W3C API, the URL is www.w3.org/TR/websockets though) Web Socket (HTML5 Demos - html5demos.com/web-socket) Websocket (Jenkins Plugin - wiki.jenkins-ci.org/display/JENKINS/Websocket%2BPlugin) WebSockets (Used by Mozilla - developer.mozilla.org/en/WebSockets, but use WebSocket as well) Web sockets (HTML5 Working Group - www.whatwg.org/specs/web-apps/current-work/multipage/network.html) Web Sockets (Chrome Blog - blog.chromium.org/2009/12/web-sockets-now-available-in-google.html) I prefer "WebSocket" as that seems to be most common usage and used by the W3C API as well. What do you use ?

  Read the article

• What’s new in Silverlight 4 RC?

  - by pluginbaby

  I am here in Las Vegas for MIX10 where Scott Guthrie announced today the release of Silverlight 4 RC and the Visual Studio 2010 tools. You can now install VS2010 RC!!! As always, downloads links are here: www.silverlight.net He also said that the final version of Silverlight 4 will come next month (so april)! 4 months ago, I wrote a blog post on the new features of Silverlight 4 beta, so… what’s new in the RC ?   Rich Text · RichTextArea renamed to RichTextBox · Text position and selection APIs · “Xaml” property for serializing text content · XAML clipboard format · FlowDirection support on Runs tag · “Format then type” support when dragging controls to the designer · Thai/Vietnamese/Indic support · UI Automation Text pattern   Networking · UploadProgress support (Client stack) · Caching support (Client stack) · Sockets security restrictions removal (Elevated Trust) · Sockets policy file retrieval via HTTP · Accept-Language header   Out of Browser (Elevated Trust) · XAP signing · Silent install and emulation mode · Custom window chrome · Better support for COM Automation · Cancellable shutdown event · Updated security dialogs   Media · Pinned full-screen mode on secondary display · Webcam/Mic configuration preview · More descriptive MediaSourceStream errors · Content & Output protection updates · Updates to H.264 content protection (ClearNAL) · Digital Constraint Token · CGMS-A · Multicast · Graphics card driver validation & revocation   Graphics and Printing · HW accelerated Perspective Transforms · Ability to query page size and printable area · Memory usage and perf improvements   Data · Entity-level validation support of INotifyDataErrorInfo for DataGrid · XPath support for XML   Parser · New architecture enables future innovation · Performance and stability improvements · XmlnsPrefix & XmlnsDefinition attributes · Support setting order-dependent properties   Globalization & Localization · Support for 31 new languages · Arabic, Hebrew and Thai input on Mac · Indic support   More … · Update to DeepZoom code base with HW acceleration · Support for Private mode browsing · Google Chrome support (Windows) · FrameworkElement.Unloaded event · HTML Hosting accessibility · IsoStore perf improvements · Native hosting perf improvements (e.g., Bing Toolbar) · Consistency with Silverlight for Mobile APIs and Tooling · SDK   - System.Numerics.dll   - Dynamic XAP support (MEF)   - Frame/Navigation refresh support   That’s a lot!   You will find more details on the following links: http://timheuer.com/blog/archive/2010/03/15/whats-new-in-silverlight-4-rc-mix10.aspx http://www.davidpoll.com/2010/03/15/new-in-the-silverlight-4-rc-xaml-features/   Technorati Tags: Silverlight

  Read the article

• GDC 2012: The Bleeding Edge of Open Web Tech

  GDC 2012: The Bleeding Edge of Open Web Tech (Pre-recorded GDC content) Web browsers from mobile to desktop devices are in a constant state of growth enabling ever richer and pervasive games. This presentation by Google software engineer Vincent Scheib focuses on the latest developments in client side web technologies, such as Web Sockets, WebGL, File API, Mouse Lock, Gamepads, Web Audio API and more. Speaker: Vincent Scheib From: GoogleDevelopers Views: 1279 31 ratings Time: 48:33 More in Science & Technology

  Read the article

• HP ProLiant DL980-Oracle TPC-C Benchmark spat

  - by jchang

  The Register reported a spat between HP and Oracle on the TPC-C benchmark. Per above, HP submitted a TPC-C result of 3,388,535 tpm-C for their ProLiant DL980 G7 (8 Xeon X7560 processors), with a cost of $0.63 per tpm-C. Oracle has refused permission to publish. Late last year (2010) Oracle published a result of 30M tpm-C for a 108 processors (sockets) SPARC cluster ($30M complete system cost). Oracle is now comparing this to the HP Superdome result from 2007 of 4M tpm-C at $2.93 per tpm-C, calling...(read more)

  Read the article

• 64-bit Archives Needed

  - by user9154181

  A little over a year ago, we received a question from someone who was trying to build software on Solaris. He was getting errors from the ar command when creating an archive. At that time, the ar command on Solaris was a 32-bit command. There was more than 2GB of data, and the ar command was hitting the file size limit for a 32-bit process that doesn't use the largefile APIs. Even in 2011, 2GB is a very large amount of code, so we had not heard this one before. Most of our toolchain was extended to handle 64-bit sized data back in the 1990's, but archives were not changed, presumably because there was no perceived need for it. Since then of course, programs have continued to get larger, and in 2010, the time had finally come to investigate the issue and find a way to provide for larger archives. As part of that process, I had to do a deep dive into the archive format, and also do some Unix archeology. I'm going to record what I learned here, to document what Solaris does, and in the hope that it might help someone else trying to solve the same problem for their platform. Archive Format Details Archives are hardly cutting edge technology. They are still used of course, but their basic form hasn't changed in decades. Other than to fix a bug, which is rare, we don't tend to touch that code much. The archive file format is described in /usr/include/ar.h, and I won't repeat the details here. Instead, here is a rough overview of the archive file format, implemented by System V Release 4 (SVR4) Unix systems such as Solaris: Every archive starts with a "magic number". This is a sequence of 8 characters: "!<arch>\n". The magic number is followed by 1 or more members. A member starts with a fixed header, defined by the ar_hdr structure in/usr/include/ar.h. Immediately following the header comes the data for the member. Members must be padded at the end with newline characters so that they have even length. The requirement to pad members to an even length is a dead giveaway as to the age of the archive format. It tells you that this format dates from the 1970's, and more specifically from the era of 16-bit systems such as the PDP-11 that Unix was originally developed on. A 32-bit system would have required 4 bytes, and 64-bit systems such as we use today would probably have required 8 bytes. 2 byte alignment is a poor choice for ELF object archive members. 32-bit objects require 4 byte alignment, and 64-bit objects require 64-bit alignment. The link-editor uses mmap() to process archives, and if the members have the wrong alignment, we have to slide (copy) them to the correct alignment before we can access the ELF data structures inside. The archive format requires 2 byte padding, but it doesn't prohibit more. The Solaris ar command takes advantage of this, and pads ELF object members to 8 byte boundaries. Anything else is padded to 2 as required by the format. The archive header (ar_hdr) represents all numeric values using an ASCII text representation rather than as binary integers. This means that an archive that contains only text members can be viewed using tools such as cat, more, or a text editor. The original designers of this format clearly thought that archives would be used for many file types, and not just for objects. Things didn't turn out that way of course — nearly all archives contain relocatable objects for a single operating system and machine, and are used primarily as input to the link-editor (ld). Archives can have special members that are created by the ar command rather than being supplied by the user. These special members are all distinguished by having a name that starts with the slash (/) character. This is an unambiguous marker that says that the user could not have supplied it. The reason for this is that regular archive members are given the plain name of the file that was inserted to create them, and any path components are stripped off. Slash is the delimiter character used by Unix to separate path components, and as such cannot occur within a plain file name. The ar command hides the special members from you when you list the contents of an archive, so most users don't know that they exist. There are only two possible special members: A symbol table that maps ELF symbols to the object archive member that provides it, and a string table used to hold member names that exceed 15 characters. The '/' convention for tagging special members provides room for adding more such members should the need arise. As I will discuss below, we took advantage of this fact to add an alternate 64-bit symbol table special member which is used in archives that are larger than 4GB. When an archive contains ELF object members, the ar command builds a special archive member known as the symbol table that maps all ELF symbols in the object to the archive member that provides it. The link-editor uses this symbol table to determine which symbols are provided by the objects in that archive. If an archive has a symbol table, it will always be the first member in the archive, immediately following the magic number. Unlike member headers, symbol tables do use binary integers to represent offsets. These integers are always stored in big-endian format, even on a little endian host such as x86. The archive header (ar_hdr) provides 15 characters for representing the member name. If any member has a name that is longer than this, then the real name is written into a special archive member called the string table, and the member's name field instead contains a slash (/) character followed by a decimal representation of the offset of the real name within the string table. The string table is required to precede all normal archive members, so it will be the second member if the archive contains a symbol table, and the first member otherwise. The archive format is not designed to make finding a given member easy. Such operations move through the archive from front to back examining each member in turn, and run in O(n) time. This would be bad if archives were commonly used in that manner, but in general, they are not. Typically, the ar command is used to build an new archive from scratch, inserting all the objects in one operation, and then the link-editor accesses the members in the archive in constant time by using the offsets provided by the symbol table. Both of these operations are reasonably efficient. However, listing the contents of a large archive with the ar command can be rather slow. Factors That Limit Solaris Archive Size As is often the case, there was more than one limiting factor preventing Solaris archives from growing beyond the 32-bit limits of 2GB (32-bit signed) and 4GB (32-bit unsigned). These limits are listed in the order they are hit as archive size grows, so the earlier ones mask those that follow. The original Solaris archive file format can handle sizes up to 4GB without issue. However, the ar command was delivered as a 32-bit executable that did not use the largefile APIs. As such, the ar command itself could not create a file larger than 2GB. One can solve this by building ar with the largefile APIs which would allow it to reach 4GB, but a simpler and better answer is to deliver a 64-bit ar, which has the ability to scale well past 4GB. Symbol table offsets are stored as 32-bit big-endian binary integers, which limits the maximum archive size to 4GB. To get around this limit requires a different symbol table format, or an extension mechanism to the current one, similar in nature to the way member names longer than 15 characters are handled in member headers. The size field in the archive member header (ar_hdr) is an ASCII string capable of representing a 32-bit unsigned value. This places a 4GB size limit on the size of any individual member in an archive. In considering format extensions to get past these limits, it is important to remember that very few archives will require the ability to scale past 4GB for many years. The old format, while no beauty, continues to be sufficient for its purpose. This argues for a backward compatible fix that allows newer versions of Solaris to produce archives that are compatible with older versions of the system unless the size of the archive exceeds 4GB. Archive Format Differences Among Unix Variants While considering how to extend Solaris archives to scale to 64-bits, I wanted to know how similar archives from other Unix systems are to those produced by Solaris, and whether they had already solved the 64-bit issue. I've successfully moved archives between different Unix systems before with good luck, so I knew that there was some commonality. If it turned out that there was already a viable defacto standard for 64-bit archives, it would obviously be better to adopt that rather than invent something new. The archive file format is not formally standardized. However, the ar command and archive format were part of the original Unix from Bell Labs. Other systems started with that format, extending it in various often incompatible ways, but usually with the same common shared core. Most of these systems use the same magic number to identify their archives, despite the fact that their archives are not always fully compatible with each other. It is often true that archives can be copied between different Unix variants, and if the member names are short enough, the ar command from one system can often read archives produced on another. In practice, it is rare to find an archive containing anything other than objects for a single operating system and machine type. Such an archive is only of use on the type of system that created it, and is only used on that system. This is probably why cross platform compatibility of archives between Unix variants has never been an issue. Otherwise, the use of the same magic number in archives with incompatible formats would be a problem. I was able to find information for a number of Unix variants, described below. These can be divided roughly into three tribes, SVR4 Unix, BSD Unix, and IBM AIX. Solaris is a SVR4 Unix, and its archives are completely compatible with those from the other members of that group (GNU/Linux, HP-UX, and SGI IRIX). AIX AIX is an exception to rule that Unix archive formats are all based on the original Bell labs Unix format. It appears that AIX supports 2 formats (small and big), both of which differ in fundamental ways from other Unix systems: These formats use a different magic number than the standard one used by Solaris and other Unix variants. They include support for removing archive members from a file without reallocating the file, marking dead areas as unused, and reusing them when new archive items are inserted. They have a special table of contents member (File Member Header) which lets you find out everything that's in the archive without having to actually traverse the entire file. Their symbol table members are quite similar to those from other systems though. Their member headers are doubly linked, containing offsets to both the previous and next members. Of the Unix systems described here, AIX has the only format I saw that will have reasonable insert/delete performance for really large archives. Everyone else has O(n) performance, and are going to be slow to use with large archives. BSD BSD has gone through 4 versions of archive format, which are described in their manpage. They use the same member header as SVR4, but their symbol table format is different, and their scheme for long member names puts the name directly after the member header rather than into a string table. GNU/Linux The GNU toolchain uses the SVR4 format, and is compatible with Solaris. HP-UX HP-UX seems to follow the SVR4 model, and is compatible with Solaris. IRIX IRIX has 32 and 64-bit archives. The 32-bit format is the standard SVR4 format, and is compatible with Solaris. The 64-bit format is the same, except that the symbol table uses 64-bit integers. IRIX assumes that an archive contains objects of a single ELFCLASS/MACHINE, and any archive containing ELFCLASS64 objects receives a 64-bit symbol table. Although they only use it for 64-bit objects, nothing in the archive format limits it to ELFCLASS64. It would be perfectly valid to produce a 64-bit symbol table in an archive containing 32-bit objects, text files, or anything else. Tru64 Unix (Digital/Compaq/HP) Tru64 Unix uses a format much like ours, but their symbol table is a hash table, making specific symbol lookup much faster. The Solaris link-editor uses archives by examining the entire symbol table looking for unsatisfied symbols for the link, and not by looking up individual symbols, so there would be no benefit to Solaris from such a hash table. The Tru64 ld must use a different approach in which the hash table pays off for them. Widening the existing SVR4 archive symbol tables rather than inventing something new is the simplest path forward. There is ample precedent for this approach in the ELF world. When ELF was extended to support 64-bit objects, the approach was largely to take the existing data structures, and define 64-bit versions of them. We called the old set ELF32, and the new set ELF64. My guess is that there was no need to widen the archive format at that time, but had there been, it seems obvious that this is how it would have been done. The Implementation of 64-bit Solaris Archives As mentioned earlier, there was no desire to improve the fundamental nature of archives. They have always had O(n) insert/delete behavior, and for the most part it hasn't mattered. AIX made efforts to improve this, but those efforts did not find widespread adoption. For the purposes of link-editing, which is essentially the only thing that archives are used for, the existing format is adequate, and issues of backward compatibility trump the desire to do something technically better. Widening the existing symbol table format to 64-bits is therefore the obvious way to proceed. For Solaris 11, I implemented that, and I also updated the ar command so that a 64-bit version is run by default. This eliminates the 2 most significant limits to archive size, leaving only the limit on an individual archive member. We only generate a 64-bit symbol table if the archive exceeds 4GB, or when the new -S option to the ar command is used. This maximizes backward compatibility, as an archive produced by Solaris 11 is highly likely to be less than 4GB in size, and will therefore employ the same format understood by older versions of the system. The main reason for the existence of the -S option is to allow us to test the 64-bit format without having to construct huge archives to do so. I don't believe it will find much use outside of that. Other than the new ability to create and use extremely large archives, this change is largely invisible to the end user. When reading an archive, the ar command will transparently accept either form of symbol table. Similarly, the ELF library (libelf) has been updated to understand either format. Users of libelf (such as the link-editor ld) do not need to be modified to use the new format, because these changes are encapsulated behind the existing functions provided by libelf. As mentioned above, this work did not lift the limit on the maximum size of an individual archive member. That limit remains fixed at 4GB for now. This is not because we think objects will never get that large, for the history of computing says otherwise. Rather, this is based on an estimation that single relocatable objects of that size will not appear for a decade or two. A lot can change in that time, and it is better not to overengineer things by writing code that will sit and rot for years without being used. It is not too soon however to have a plan for that eventuality. When the time comes when this limit needs to be lifted, I believe that there is a simple solution that is consistent with the existing format. The archive member header size field is an ASCII string, like the name, and as such, the overflow scheme used for long names can also be used to handle the size. The size string would be placed into the archive string table, and its offset in the string table would then be written into the archive header size field using the same format "/ddd" used for overflowed names.

  Read the article

• Looking to trade a 1U HP Proliant DL360 G5 in exchange for a small linux VPS

  - by user597875

  I have a 1U HP Proliant DL360 G5 that I have no place to rack and would like to trade it for a small linux VPS. If interested let me know... Here are the specs of the server: Model: Intel Xeon CPU 5150 @ 2.66GHz, 4MB L2 Cache Processor Speed: 2.7GHz Processor Sockets: 2 Processor Cores per Socket: 2 Logical Processors: 4 8GB of memory 4x72GB 10k SAS drives Manufacturer: HP Model: Proliant DL360 G5 BIOS Version: P58

  Read the article

• Apache / MySql is not running. What is wrong?

  - by Valeriu

  I installed lampp / xampp on my Ubuntu 12.04. After installing, Apache and MySQL were running properly. Now, they're not. Here's what I get when I try to run apache: Command: /etc/init.d/apache2 start Result: * Starting web server apache2 /usr/sbin/apache2ctl: 87: ulimit: error setting limit (Operation not permitted) (13)Permission denied: make_sock: could not bind to address 0.0.0.0:80 no listening sockets available, shutting down Unable to open logs Action 'start' failed. The Apache error log may have more information.

  Read the article

• Code Design question, circular reference across classes?

  - by dsollen

  I have no code here, as this is more of a design question (I assume this is still the best place to ask it). I have a very simple server in java which stores a mapping between certain values and UUID which are to be used by many systems across multiple platforms. It accepts a connection from a client and creates a clientSocket which stores the socket and all the other relevant data unique to that connection. Each clientSocket will run in their own thread and will block on the socket waiting for a read. I expect very little strain on this system, it will rarely get called, but when it does get a call it will need to respond quickly and due to the risk of it having a peak time with multiple calls coming in at once threaded is still better. Each thread has a reference to a Mapper class which stores the mapping of UUID which it's reporting to others (with proper synchronization of course). This all works until I have to add a new UUID to the list. When this happens I want to report to all clients that care about that particular UUID that a new one was added. I can't multicast (limitation of the system I'm running on) so I'm having each socket send the message to the client through the established socket. However, since each thread only knows about the socket it's waiting on I didn't have a clear method of looking up every thread/socket that cares about the data to inform them of the new UUID. Polling is out mostly because it seems a little too convoluted to try to maintain a list of newly added UUID. My solution as of now is to have the 'parent' class which creates the mapper class and spawns all the threads pass itself as an argument to the mapper. Then when the mapper creates a new UUID it can make a call to the parent class telling it to send out updates to all the other sockets that care about the change. I'm concerned that this may be a bad design due to the use of a circular reference; parent has a reference to mapper (to pass it to new ClientSocket threads) and mapper points to parent. It doesn't really feel like a bad design to me but I wanted to check since circular references are suppose to be bad. Note: I realize this means that the thread associated with whatever socket originally received the request that spawned the creation of a UUID is going to pay the 'cost' of outputting to all the other clients that care about the new UUID. I don't care about this; as I said I suspect the client to receive only intermittent messages. It's unlikely for one socket to receive multiple messages at one time, and there won't be that many sockets so it shouldn't take too long to send messages to each of them. Perhaps later I'll fix the fact that I'm saddling higher work load on whatever unfortunate thread gets the first request; but for now I think it's fine.

  Read the article

• Volume control doesn't work for headphones

  - by Hendekagon

  Fresh install of 11.10 and the gnome panel's volume control doesn't work for headphones but does work for speakers on my laptop. In sound settings I have Internal Audio Analogue Stereo selected for output (Output tab) and Analogue Speakers selected for Connector. When I plug headphones in, the volume control doesn't work and the volume is maximum through the headphones. On a side note, only one of my two headphone sockets produces sound too (whereas both worked in 10.04)

  Read the article

• Which game engine for HTML5 + Node.js

  - by Chrene

  I want to create a realtime multiplayer game using and HTML5. I want to use node.js as the server, and I only need to be able to render images in a canvas, play some sounds, and do some basic animations. The gameloop should be done in the server, and the client should do callback via sockets to render the canvas. I am not going to spend any money on the engine, and I don't want to use cocos2d-javascript.

  Read the article

• Does anybody develops Java desktop applications? [closed]

  - by Eirc man

  I was just wondering if there are there developers making java software for desktops. Is it even worth it, do any developers do that for living. I am making a chat application using sockets and and java GUI, just for fun, but then I wanted to see some examples of desktop apps, but did not find many. I have heard that Netbeans, is made using java, but the Netbeans in my Windows to me it seems like any other native Windows application

  Read the article

• How to run an application using sudo without a password?

  - by tutuca

  ... but still be required for applications that need admin privilegies? In order to allow the following: $ apache2ctl restart httpd not running, trying to start (13)Permission denied: make_sock: could not bind to address 0.0.0.0:80 no listening sockets available, shutting down Unable to open logs $ sudo !! sudo apache2ctl restart #no password asked $ #works! For reference I've seen this setup on amazon's e3 instances Any idea?

  Read the article

• Why Do You Need SSL Certificate

  SSL (Secure Sockets Layer) is an encrypting modus operandi that ensures the en route security of the personal details processed by the browser to the server. We all know that online shopping is prefe... [Author: Jack Melde - Computers and Internet - May 01, 2010]

  Read the article

< Previous Page | 39 40 41 42 43 44 45 46 47 48 49 50  | Next Page >