Simple update check function

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Introduction

Almost all programs that are available today have a feature that checks for software updates using the internet. This is a convenient way for both the user and the developer: You don't have to contact all the users (if you know them...) when a new version is available. And the user can be sure to always have the newest version.

In this article I'd like to focus on small programs (e.g. only 1 executable and no nescessary installation program) and developers who have just a simple web space without the possibility to use scripts (only static web pages). Also this code only shows a web page and does not automatically download or install files.

The basic thing we have to do is very simple: Connect to a web site, ask for the newest version, compare it to the current version, and in case there is an update ask the user to download it. You - as the developer - have to use correct version information in your code and update the internet file whenever an update is available.

Program version

Ever looked at the version block of your code in the resource file? This resource consists of two major blocks: A language-independent information on the top containing file version etc. and some blocks where text information can be stored like the copyright. This code only uses the fixed block (FILEVERSION) at the top of this resource. Please be sure to update this block any time you want to release a new version!

What this class does

The new class CUpdateCheck has 1 main function: download a web site and check for updates! If you don't want to change any behaviour you simply use the class "as is" - that's all (besides adding the language-dependant strings). The class has two helper function GetFileVersion()to get the applications File version and GotoURL() which simply opens a web page in the default browser. I got the code for GotoURL() somewhere on the web, so when you are the author please inform me to put your names to the credits.

Using the code, allow auto-updates

[1]: Add a new menu item to your application and handle it in your CWinApp drived class. This could look like this:

void CMyApp::OnAppCheckupdate()
{
  CUpdateCheck checkUpdate;
  checkUpdate.Check(IDS_UPDATE);
}

where the string IDS_UPDATE is e.g. http://www.mywebsite.xxx/update.txt

In case you want to check automatically for updates each time the user start your application put the lines above in the InitInstance function. Or write the last date you checked for updates to the registry and only check once each week. ....

[2]: Add a few strings to the string table:

IDS_UPDATE_AVAILABLE	You currently use version %u.%u of this program. The newest version %u.%u is available online. Do you want to see more information?
IDS_UPDATE_NO	No Updates available.
IDS_UPDATE_NOCHECK	Unable to check for updates.

[3]: Put a file on your webspace (located as referred in IDS_UPDATE) which has the following syntax:

Major Version|Minor Version|URL for Update page

So when your program has currently the version 1,1,0,0 and you want to offer an update to 3,4,0,0 which is available for download at http://www.mydomain.com/updateinfo.html the file should be

3|4|http://www.mydomain.com/updateinfo.html

Limitations

• The file on your web site has to be less than 512 characters
• Only the two leftmost parts of the version info are used. The lower two numbers are normally used as a "Build number" and have no effect on this class
• No automatic download is offered, the user has to download the files from your site and copy/install them

History

01.11.2003: Initial release

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Subject   Author  Date  More generic programming? MaartenEngels 5:55 18 Aug '07   Hi Alexander, Thank you example code; I think it is very usefull. With your code, and with many code-examples in general, I feel that they can be even more of use when programmed more generic; i.e. without any compiler/mfc/vcl kinda dependencies. You could, for example, use std::string instead of CString and, in the case of your example, leave out any user-interface stuff (don't launch any message boxes, just return the result as an enum or so). This would allow programmers with a different or no IDE to apply your code much easier. Keep up the good work! Best regards, Maarten Engels Sign In·View Thread·PermaLink 2.00/5 (1 vote) CheckForUpdates - Security / Legal aspects Yogesh P. Dhakad 20:42 1 Feb '07   Dear Alexander, It’s indeed a very simple and workable solution giving a basic simple framework to implement the “CheckForUpdates” functionality in our products. I have two questions; 1) I presume that “CheckForUpdates” functionality cannot be FORCED in our MFC (desktop based) products. But this I mean all the good products will keep this option turned on while deploying the product on to the customer but the customer later has the choice to disable AUTO – CheckForUpdates on the application launch. Our good product would then allow the customer to trigger the “CheckForUpdates” via a menu item under the Help menu. This is very commonly adapted practice. Now my question was IS IT LEGAL TO ALWAYS DO (FORCEFULLY) CHECKFORUPDATES ON THE APPLICATION LAUNCH? 2) Is CheckForUpdates a ONE-SIDED data flow? Mostly we see that our product READS information from our Product_Website. Can the reverse happen (may be using INTERNETWRITEFILE() of FTP) i.e. Product collects the necessary information (may be a 32 bit encrypted string) and sends that information while making the hand-shaking with the Product_Website. Again I understand all this is possible but my question is – does it violate any LEGAL aspects of the internet security at the customer’s end. Basically I am trying to loudly discuss – the best mechanism by virtue of which EACH COPY of our PRODUCT communicates back to our Product_Website about many different things – but prominently – whether the license being used is authentic – i.e Is this customer having a VALID License or Pirated? I wish to get some insights from you on this. Best regards, Yogesh Dhakad Sign In·View Thread·PermaLink Re: CheckForUpdates - Security / Legal aspects Yogesh P. Dhakad 20:50 1 Feb '07   Just one quick addition to rule out common doubt - my product is having a robust () licensing mechanism and this is in-built into the product. Thus the licensing mechanism itself does NOT need to cummunicate to the webserver etc. To cut it short - my product is designed such that it SHOULD run on a customer's machine that is NOT connected to the internet. I hope you could reply back with some good information / links. Regards, Yogesh Sign In·View Thread·PermaLink 2.00/5 (1 vote) Re: CheckForUpdates - Security / Legal aspects Alexander Bischofberger 1:04 4 Feb '07   Hi! I'm not quite sure if I understood you right. 1) I'm not a lawyer, so I can not guarantee that an automatic update check is legal in any country you ship your software. My personal optinion is that if you clearly point this out in your manual there should be no problem. Otherwise you could add a checkbox to your installer and let the user decide wether to use this or not. 2) The data flow is (more or less) one-sided, as ony other HTTP request. You can transfer small portions of data (e.g. software version, application name, even a serial number or better a hash of a serial) using the agent string of the request. You know: When looking at your web log you can see how many users used e.g. IE 5.5 as an agent. Why not transfer "MyApp 1.0" as the agent? But before transferring any personal data using this way you should really inform the user what's going on... Ciao, Alex Sign In·View Thread·PermaLink Re: CheckForUpdates - Security / Legal aspects Yogesh P. Dhakad 9:36 7 Feb '07   Thanks Alex for giving a prompt and satisfying reply. Regards Sign In·View Thread·PermaLink Excellent, slight fix though John-Lucas Brown 6:59 30 Jan '07   Just what i wanted, but I've extended it on my machine to run a php script on the server to return the latest version (and other available versions) and i've found that InternetReadFile can read things in chunks and not return teh whole file on the first call. I know this is unlikely with such a small file being loaded, b ut over a very slow dialup you may find that it will not read the whole file. /**********************************************************/ bool InternetReadWholeFile(HINTERNET hUrl,LPVOID lpBuffer,DWORD dwNumberOfBytesToRead,LPDWORD lpNumberOfBytesRead) { DWORD dwRead=0; BYTE szBuffer[512]; memset(lpBuffer,0,dwNumberOfBytesToRead); *lpNumberOfBytesRead = 0; do{ if (!InternetReadFile(hUrl,szBuffer,sizeof(szBuffer),&dwRead)) dwRead = 0; if (dwRead!=0){ if (*lpNumberOfBytesRead + dwRead > dwNumberOfBytesToRead) return false;//too much data for the buffer memcpy(&((char *)lpBuffer)[*lpNumberOfBytesRead],szBuffer,dwRead); *lpNumberOfBytesRead+=dwRead; } }while (dwRead != 0 && strchr((char *)lpBuffer,EOF)==NULL); return strchr((char *)lpBuffer,EOF)==NULL; } I used this function instead. Cheers, John. Sign In·View Thread·PermaLink Re: Excellent, slight fix though Alexander Bischofberger 8:53 30 Jan '07   Hi! First of all: you are right, the original function could loose data. I did some tests and always got enough bytes that include the (very small) text string from the download. But there is no guarantee that this will always work, so I'd suggest to use your code above to replace my original code. I'll put your code inside the class during the next update - which could take quite a long time... If you do not want me to do this please send a reply. Ciao, Alex Sign In·View Thread·PermaLink Re: Excellent, slight fix though John-Lucas Brown 23:32 30 Jan '07   Hi, No problem at all, I don't mind you using the code, I just wanted to flag it up for people in case they extend it to download a larger file. I scratched my head for a while trying to work out why sometimes it got it all, and othertimes it got very little. But as you say that it is only downloading a very small file so unless they're using a wet peice of string for their internet connection then the function will always return the full line. Cheers, John. Sign In·View Thread·PermaLink Very good code! Very simple, easy for implement and use! krasi_top 8:39 17 Apr '06   Hi Alex! This source code is nice and easyes for use! I use this code in my application! It absolutely FREE for use (Web Update Wizard - cost 129 $ for single application??? What is this?). Thanks for this excellent class. More commercial products using the similar method for update check! Thanks, Krasimir Stoychev! Sign In·View Thread·PermaLink Juande jdmanjon 22:53 23 Nov '03   Run-Time Check Failure #2 - Stack around the variable 'szBuffer' was corrupted. (VC7 assert) the function doesn't check the max len (512) of the buffer before adding "\n" Change the line: szBuffer[dwRead] = 0; with: szBuffer[ (dwRead<512 ? dwRead : 511)] = 0; Juande Sign In·View Thread·PermaLink Shameless plug for Web Update Wizard peterboulton 8:02 18 Nov '03   The subject says it all. If you would like something more comprehensive, but low cost, which can download and install the updates (and much more), yet only needs a single DLL call to build into your software and runs on any isp / webserver, please check out the Web Update Wizard at http://www.PowerProgrammer.co.uk. (I hope no one is offended by this plug - it seems relevant given the subject matter of this article.) Thank you. Pete Sign In·View Thread·PermaLink 1.44/5 (3 votes) Re: Shameless plug for Web Update Wizard mier 0:27 19 Nov '03   ...and for only $400 you can have all that!! Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard peterboulton 1:08 19 Nov '03   Not clear what your point is, but assume you don't like the plug! Please consider what the Web Update Wizard does and compare it to alternatives such as Installshield's. The Web Update Wizard can be used on any number of projects for a (1 developer) cost of $400. Installshield's service starts more expensive, is recurrent, and depends on their servers. The Web Update Wizard is clearly not for everyone, but it does represent a cost-effective route to delivering this functionality with little effort and at low cost, and existing users are enthusiastic. $400 = 1 developer day? See if you can write something like the Web Update Wizard in 1 day - if you can then clearly you don't need the Web Update Wizard. Otherwise, surely it's worth consideration? I will not add any more to this thread, whatever comes below this posting. I posted the plug because it was relevant to viewers who might be interested in adding 'update over the web' to their apps. I am sorry if this has offended anyone - that was not the intention. Sign In·View Thread·PermaLink 1.00/5 (1 vote) Re: Shameless plug for Web Update Wizard Sean O'Brien 13:12 22 Nov '03   What about the Gnucleus method for updating? It offers the same solution and is completely free. There's even a tutorial here on CodeProject: http://www.codeproject.com/useritems/gnucleus.asp Sean O'Brien Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard peterboulton 3:09 23 Nov '03   Does Gnucleus allow users without Admin rights to securely update to Program Files folder etc? Only Web Update Wizard does do this! Most corporates tie down Program Files / Windows folders etc. and a process running in the user's security context will not be able to update itself or anything else in these locations. Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard Sean O'Brien 11:36 23 Nov '03   That feature wouldn't be too hard to implement, and would only matter on nt/xp systems. I hardly think that's worth $400 for a single developer. Please, advertise elsewhere. Sean O'Brien Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard peterboulton 23:05 23 Nov '03   Clearly there are people out there who disagree with you Sean. Over and definitely out. (Sorry you feel so strongly about this issue!) Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard Hockey 21:46 15 May '04   free advertising on CP is a no-no How do I print my voice mail? Sign In·View Thread·PermaLink 5.00/5 (2 votes) Re: Shameless plug for Web Update Wizard peterboulton 5:21 16 May '04   I've already apologised for any offense caused by my posting. What more can I do? I am not an axe murderer, I am kind to children and old ladies. Give me a break! I had thought this thread was well and truly put to bed, but I guess there are self-appointed net police popping up all the time. Perhaps they should read the whole thread though? That is, as already stated, I have already sincerely apologised, and in addition some (in my opinion) wholly reasonable people have stated that the posting at least helped increase their awareness of the range of available options. To complete my punishment, I am slitting my wrists as I type this.... Happy? Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard Hockey 6:03 16 May '04   peterboulton wrote: I've already apologised for any offense caused by my posting Yeah your right...so I suppose I should appologize My sincere appologies However I didn't really mean my remark to come across like it obviosuly did...I would make shameless plugs too (if I had a product to push). It was more of a tisk tisk kinda remark...and the fact you appologized helped...I hate it when people post ads in the forums and just ignore criticism... When I read posts i'm 99% of the time looking for FREE answers to a problem, not some commercial bulls*it...i'm a very impatient programmer, wanting answers now peterboulton wrote: I am not an axe murderer, I am kind to children and old ladies. Give me a break! <br/> There you go A bit of HTML humor to lesson any grief I may have caused you...(it's even xhtml compliant) peterboulton wrote: wholly reasonable people have stated that the posting at least helped increase their awareness of the range of available options IHMO just don't do it again (this way)...there are much better ways to do it...like the old advertising adage goes...one negative customer is worse than something...something... Personally I have looked into doing what you have done I just haven;'t gotten around to it yet... so it wouldn't be much good to me, but obviously some people appreciated it!!! If you want to advertise a product like yours on CP do like I will eventually do...have a link inside your sig and become highly active in the CP community...look at Mike Dunn for an example...he's helpful, knowledgable, written tons of high quality articles and every time he makes a post he makes an incognito plug for his products He's a smart dude... What you could do is post the LCS code (w/ LCS tutorial) you use to differentiate your two files as an article on CP (there are already a few, so read them and make yours better) That'll guarunteed get people checking out your product and it's considered ethical on CP (so i've noticed) Anyways man, I appologize for any feelings I may have disturbed and I really didn't mean it that way, it was just me browsing the bowels of CP at 4 in the morning with nothing else to do... Cheers How do I print my voice mail? Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard Alexander Bischofberger 1:35 26 Nov '03   To end this discussion: First of all I'm not too happy to have an advertisement in this article. I think that my class and the promoted product focus completly different developers. And if it's worth 400 $ or not is up to you... Ciao, Alex Sign In·View Thread·PermaLink 5.00/5 (2 votes) Re: Shameless plug for Web Update Wizard peterboulton 3:54 26 Nov '03   Alex, I am truly sorry for any offense caused to you or any readers of your contribution. What more can I say? Pete Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard Tony Leotta 16:58 24 Jan '04   I found the plug and the link to Gnucleus Tutorial (Part 1) very helpful. I think the shamless plug was great because I found out alot about Free and Commercial products. I have products to deploy and I need help doing it. Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard John Marino 23:27 20 Apr '04   I agree with Tony. I found the article informative, although my needs exceed the limitations of the class. I didn't mind Peter's plug. If my project had double or triple the users, then $400 would indeed be a reasonable price to pay. Damn, I got off topic. The point was that I, like Tony, gained a lot of information here today from the article and more importantly, some alternatives mentioned in this thread. Sign In·View Thread·PermaLink Re: Shameless plug for Web Update Wizard The Bug 2:40 5 Oct '04   Yeah, look at the screenshot at their site: 1 sec(576.0KB of 1.61MB copied) Transfer rate *583KB/Sec* Can it be true? Can. Little detail but, $400... IMHO Sign In·View Thread·PermaLink

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