BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  downloading with wininet          BorlandTalk.com Forum Index -> C++ Builder (Internet Web) View previous topic :: View next topic   Author Message Boba Guest Posted: Tue Jan 02, 2007 9:10 am    Post subject: downloading with wininet Happy New Year! I'm trying to figure out what's wrong with the following code. Please help. Thanks. void DownloadFile( LPCSTR szServerName, LPCSTR szFileName ){ HINTERNET hHttpNet, hHttpSession, hHttpRequest; DWORD dwDataSize, dwBytesDownloaded; LPCSTR szAcceptTypes[] = { "*.*", NULL }; BYTE Buffer[1024]; hHttpNet = InternetOpen( "Microsoft Internet Explorer", INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0 ); if( hHttpNet ){ hHttpSession = InternetConnect( hHttpNet, szServerName, INTERNET_DEFAULT_HTTP_PORT, "anonymous", "", INTERNET_SERVICE_HTTP, 0, 0 ); if( hHttpSession ){ hHttpRequest = HttpOpenRequest( hHttpSession, "GET", szFileName, "HTTP/1.1", NULL, szAcceptTypes, INTERNET_FLAG_RELOAD, 0 ); if( hHttpRequest ){ if( HttpSendRequest( hHttpRequest, NULL, 0, NULL, 0 ) ){ do{ if( InternetQueryDataAvailable( hHttpRequest, &dwDataSize, 0, 0 ) ){ if( InternetReadFile( hHttpRequest, (LPVOID)Buffer, sizeof(Buffer), &dwBytesDownloaded ) ){ /*write the data*/ }//if( InternetReadFile }//if( InternetQueryDataAvailable( } while( dwBytesDownloaded ); }//if( HttpSendRequest InternetCloseHandle( hHttpRequest ); }//if( hHttpRequest ) InternetCloseHandle( hHttpSession ); }//if( hHttpSession ) InternetCloseHandle( hHttpNet ); }//if( hHttpNet ) }//DownloadFile Back to top Remy Lebeau (TeamB) Guest Posted: Tue Jan 02, 2007 3:27 pm    Post subject: Re: downloading with wininet "Boba" <Boba (AT) somewhere (DOT) world> wrote in message news:4599f9c5 (AT) newsgroups (DOT) borland.com... Quote: LPCSTR szAcceptTypes[] = { "*.*", NULL }; That is wrong. HttpOpenRequest() expects a media ContentType mask, not a filename mask. At the verly least, you need to change *.*" to "*/*", ie: LPCSTR szAcceptTypes[] = { "*/*", NULL }; Quote: hHttpRequest = HttpOpenRequest( hHttpSession, "GET", szFileName, "HTTP/1.1", NULL, szAcceptTypes, INTERNET_FLAG_RELOAD, 0 ); What exactly are you passing as the szFileName? It needs to be a URL relative to the root of the server, not a local file path. Why are you passing the server name separately from the filename in the first place? You should use InternetCraskUrl() to convert a single full URL string into the individual parts that InternetOpen(), InternetConnect(), and HttpOpenRequest() are all expecting. Quote: do{ if( InternetQueryDataAvailable( hHttpRequest, &dwDataSize, 0, 0 ) ){ I suggest you use HttpQueryInfo() to retreive the size of the data before then entering the loop. That way you know when to stop looping properly. Gambit Back to top Boba Guest Posted: Tue Jan 02, 2007 10:36 pm    Post subject: Re: downloading with wininet "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:459a2c13$1 (AT) newsgroups (DOT) borland.com... Quote: ... LPCSTR szAcceptTypes[] = { "*.*", NULL }; That is wrong. HttpOpenRequest() expects a media ContentType mask, not a filename mask. At the verly least, you need to change *.*" to "*/*", ie: ....hmmm... both gave the same result. i wish i knew why. Quote: LPCSTR szAcceptTypes[] = { "*/*", NULL }; hHttpRequest = HttpOpenRequest( hHttpSession, "GET", szFileName, "HTTP/1.1", NULL, szAcceptTypes, INTERNET_FLAG_RELOAD, 0 ); What exactly are you passing as the szFileName? It needs to be a URL relative to the root of the server, not a local file path. here's a sample call: DownloadFile("download.microsoft.com", "/download/6/a/f/6af940c1-2774-4ebb-8546-2c83068af231/Windows2000-KB926247-x86-E NU.EXE"); Quote: Why are you passing the server name separately from the filename in the first place? that's the way 'they' want. Quote: I suggest you use HttpQueryInfo() to retreive the size of the data before then entering the loop. InternetQueryDataAvailable() is supposed to do that. Quote: That way you know when to stop looping properly. if no (more) data avalable, dwBytesDownloaded will be set 0 by the InternetReadFile() call. Back to top Remy Lebeau (TeamB) Guest Posted: Wed Jan 03, 2007 12:44 am    Post subject: Re: downloading with wininet "Boba" <Boba (AT) somewhere (DOT) world> wrote in message news:459a89d6 (AT) newsgroups (DOT) borland.com... Quote: ...hmmm... both gave the same result. i wish i knew why. Considering that none of your code is doing any error handling, you did not specify the contents of the values you are passing, and you did not specify on which line the failure is actually occuring, there is no way to diagnose your problem. You need to provide more information. Quote: here's a sample call: DownloadFile("download.microsoft.com", "/download/6/a/f/6af940c1-2774-4ebb-8546-2c83068af231/Windows2000-KB92 6247-x86-E Quote: NU.EXE"); Ok so far. Though again, there is no reason to separate the server from the path like that. You should be passing it as a single complete URL string, ie: DownloadFile("http://download.microsoft.com/download/6/a/f/6af940c1-27 74-4ebb-8546-2c83068af231/Windows2000-KB926247-x86-ENU.EXE"); Quote: I suggest you use HttpQueryInfo() to retreive the size of the data before then entering the loop. InternetQueryDataAvailable() is supposed to do that. Your looping code is wrong anyway. You are not using the value that InternetQueryDataAvailable() returns. You must read everything that InternetQueryDataAvailable() reports, or else it cannot report more data later. This is clearly stated in the documentation. You need to change your loop to something more like the following instead: BYTE Buffer[1024]; DWORD dwDataSize, dwBytesToRead, dwBytesRead, dwBytesDownloaded; dwBytesDownloaded = 0; while( InternetQueryDataAvailable(hHttpRequest, &dwDataSize, 0, 0) ) { if( dwDataSize == 0 ) break; do { dwNumToRead = min(dwDataSize, sizeof(Buffer)); if( !InternetReadFile(hHttpRequest, Buffer, dwBytesToRead, &dwBytesRead) ) break; // write the data... dwDataSize -= dwBytesRead; dwBytesDownloaded += dwBytesRead; } while( dwDataSize != 0 ); } However, I strongly suggest you use HttpQueryInfo() instead of InternetQueryDataAvailable(). Then you need only 1 loop instead of 2, since the download already knows the full size of the data ahead of time, ie: BYTE Buffer[1024]; DWORD dwDataSize, dwBytesToRead, dwBytesRead, dwBytesDownloaded, dwIndex = 0; DWORD dwLen = sizeof(dwDataSize); dwBytesDownloaded = 0; if( HttpQueryInfo(hHttpRequest, HTTP_QUERY_CONTENT_LENGTH | HTTP_QUERY_FLAG_NUMBER, &dwDataSize, &dwLen, &dwIndex) ) { while( dwDataSize != 0 ) { dwNumToRead = min(dwDataSize, sizeof(Buffer)); if( !InternetReadFile(hHttpRequest, Buffer, dwBytesToRead, &dwBytesRead) ) break; // write the data... dwDataSize -= dwBytesRead; dwBytesDownloaded += dwBytesRead; } } Gambit Back to top Boba Guest Posted: Wed Jan 03, 2007 1:29 am    Post subject: Re: downloading with wininet "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:459aac49$1 (AT) newsgroups (DOT) borland.com... Quote: ... Considering that none of your code is doing any error handling, you did not specify the contents of the values you are passing, and you did not specify on which line the failure is actually occuring, there is no way to diagnose your problem. You need to provide more information. the error checking has been stripped off to simplify the post. there is no code line where it fails: it is the result of downloading that is sometimes wrong. at random, the file i get is the 406 error message (none of the code lines report a failure). some servers never send 406; others - like the one in my sample - do it at no obvious reason for that. let say i call the function 5 times in a raw on the same file and 2 times i may get a 406.html file instead. Quote: Your looping code is wrong anyway. You are not using the value that InternetQueryDataAvailable() returns. You must read everything that InternetQueryDataAvailable() reports, or else it cannot report more data later. i do read everything (not shown for the sake of simplicity). Quote: However, I strongly suggest you use HttpQueryInfo() instead of InternetQueryDataAvailable(). i will try it shortly. Back to top Remy Lebeau (TeamB) Guest Posted: Wed Jan 03, 2007 2:30 am    Post subject: Re: downloading with wininet "Boba" <Boba (AT) somewhere (DOT) world> wrote in message news:459ab27c (AT) newsgroups (DOT) borland.com... Quote: the error checking has been stripped off to simplify the post. there is no code line where it fails: it is the result of downloading that is sometimes wrong. at random, the file i get is the 406 error message (none of the code lines report a failure). Well, you are not checking the actual response code to begin with before downloading the file. 406 is a "not acceptable" error. You have to use HttpQueryInfo() to verify the server's reply before you can decide whether the file is ok to download or not. Quote: some servers never send 406; others - like the one in my sample - do it at no obvious reason for that. I am assuming that you have not read RFC 2616 yet: Hypertext Transfer Protocol -- HTTP/1.1 http://www.ietf.org/rfc/rfc2616.txt 10.4.7 406 Not Acceptable The resource identified by the request is only capable of generating response entities which have content characteristics not acceptable according to the accept headers sent in the request. Unless it was a HEAD request, the response SHOULD include an entity containing a list of available entity characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. Depending upon the format and the capabilities of the user agent, selection of the most appropriate choice MAY be performed automatically. However, this specification does not define any standard for such automatic selection. Note: HTTP/1.1 servers are allowed to return responses which are not acceptable according to the accept headers sent in the request. In some cases, this may even be preferable to sending a 406 response. User agents are encouraged to inspect the headers of an incoming response to determine if it is acceptable. If the response could be unacceptable, a user agent SHOULD temporarily stop receipt of more data and query the user for a decision on further actions. Quote: i do read everything (not shown for the sake of simplicity). You are calling InternetReadFile() once, and only once, for each call to InternetQueryDataAvailable(). If the size of the available data is larger than your buffer, or InterntReadFile() cannot return that much data in a single call, then you are NOT reading all of the available data properly. That is why you must loop the call to InterntReadFile() to ensure all available data is read in full. Gambit Back to top Remy Lebeau (TeamB) Guest Posted: Wed Jan 03, 2007 2:36 am    Post subject: Re: downloading with wininet "Boba" <Boba (AT) somewhere (DOT) world> wrote in message news:459ac5e4 (AT) newsgroups (DOT) borland.com... Quote: i'm getting exactly the same behavior: once in a while the file downloaded is just a 406.html message. That is because your requests are wrong to begin with, and you are not checking the server's response code. Please see my other reply. Gambit Back to top Boba Guest Posted: Wed Jan 03, 2007 2:52 am    Post subject: Re: downloading with wininet "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:459aac49$1 (AT) newsgroups (DOT) borland.com... Quote: ... However, I strongly suggest you use HttpQueryInfo() instead of InternetQueryDataAvailable(). i'm getting exactly the same behavior: once in a while the file downloaded is just a 406.html message. so, how do i tell the server that my client is aware of all these MIME settings and that it does accept the MIME type of the requested page. Back to top Boba Guest Posted: Wed Jan 03, 2007 3:13 am    Post subject: Re: downloading with wininet "Remy Lebeau (TeamB)" <no.spam (AT) no (DOT) spam.com> wrote in message news:459ac541$1 (AT) newsgroups (DOT) borland.com... Quote: ... I am assuming that you have not read RFC 2616 yet: you've got that right. Quote: You are calling InternetReadFile() once, and only once, for each call to InternetQueryDataAvailable(). If the size of the available data is larger than your buffer, or InterntReadFile() cannot return that much data in a single call, then you are NOT reading all of the available data properly. That is why you must loop the call to InterntReadFile() to ensure all available data is read in full. i do loop InternetReadFile untill dwBytesDownloaded becomes 0. my problem is not in reading the file, but in convincing the server in client's ability to accept that type of file. the server responds with 406 in a very strange inconsistency, which means i've got to tell it first that i am aware of teh potential MIME problems. i don't understand why the server is not pursistant in its response and how do i create my request header properly. Back to top Remy Lebeau (TeamB) Guest Posted: Wed Jan 03, 2007 7:06 am    Post subject: Re: downloading with wininet "Boba" <Boba (AT) somewhere (DOT) world> wrote in message news:459acad3 (AT) newsgroups (DOT) borland.com... Quote: i do loop InternetReadFile untill dwBytesDownloaded becomes 0. No, you are not. I quote your original code: do{ if( InternetQueryDataAvailable( hHttpRequest, &dwDataSize, 0, 0 ) ){ if( InternetReadFile( hHttpRequest, (LPVOID)Buffer, sizeof(Buffer), &dwBytesDownloaded ) ){ /*write the data*/ }//if( InternetReadFile }//if( InternetQueryDataAvailable( } while( dwBytesDownloaded ); You are looping InternetQueryDataAvailable(), not InternetReadFile(). Again, if you do not read ALL of the data that InternetQueryDataAvailable() reports in a single call, it CANNOT report more data until the previous data queue is emptied. This is clearly stated by Microsoft's documentation: InternetQueryDataAvailable http://msdn2.microsoft.com/en-us/library/aa385100.aspx "This function returns the number of bytes of data that are available to be read immediately by a subsequent call to InternetReadFile. If there is currently no data available and the end of the file has not been reached, the request waits until data becomes available. The amount of data remaining will not be recalculated until all available data indicated by the call to InternetQueryDataAvailable is read." Read the last sentence very carefully. After you call InternetQueryDataAvailable(), you must read ALL available data before you can call InternetQueryDataAvailable() again. Quote: my problem is not in reading the file It may not be the original problem you were asking about, but it is another problem in your code nontheless that you must address properly. Quote: but in convincing the server in client's ability to accept that type of file. Had you read the RFC that I pointed you to, you would see that when a 406 reply is returned by the server, the reply data includes alternative characteristics and locations that you must use to download the content, as the original criteria you provided will not work for what you are trying to download. Gambit Back to top Boba Guest Posted: Wed Jan 03, 2007 8:35 am    Post subject: Re: downloading with wininet Thank you very much, Gambit. The information you have provided during this conversation was very helpful in resolving the problem with my code. 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