I'm using the following line to download a file, and when I do that, it's not downloading the most recent file.
HRESULT hr = URLDownloadToFile(NULL, _T("http://example.com/users.txt"), _T("users.txt"), 0, NULL);
On the first run, users.txt has 3 names in it, if you were to remove a name, and run it again it still downloads with 3 names.
I'm using remove("users.txt); to remove the file prior to download.
It is probably operating system specific, or at least you need a library for HTTP client side.
You need to read a lot more about the HTTP protocol. The formulation of your question makes me believe you don't understand much about it.
On some OSes (notably Linux and POSIX compliant ones), you can use libcurl (which is a good HTTP client free software library)
URLDownloadToFile seems to be a Windows specific thing. Did you carefully read its documentation? It is returning some error code. Do you handle hr correctly?
You can probably only get what the HTTP protocol (response from web server, for a GET HTTP request) gives you. Mostly, the MIME type of the content of the URL, the content size, and the content bytes (etc... including content encoding etc...). The fact that the content has 3 names is your understanding of it.
Try to read more about the HTTP protocol, and understand what is really going on. Are any cookies or sessions involved? Did you try to use something like telnet to manually make the HTTP exchange? Are you able to show it and understand it? What it the HTTP response code ?
If you have access to the server (e.g. using ssh) and are able to look into the log files, try to understand what exchanges happened and what HTTP status -i.e. error code- was sent back. Perhaps set up some Linux box locally for initial tests. Or setup some HTTP server locally and use http://localhost/ etc...
Related
I have a c++ project (server-side) which sends the data to the client side with the help of event source. Now for debugging purposes I have maintained a trace file (text). On all the critical areas in the c++ code where there is a fear of code-break, I have added a line which writes the "success" text to this trace file. It works fine. I can know where the code is success and where it failed.
But I am on the server side. I want to avail this facility to the client too. However, I am unsure about how to do that? Should I stream the file on web-browser, or is there any other way I can send the data "live" to web-browser?
I checked this link, however, I am not sure if I can use this. http://www.tutorialspoint.com/cplusplus/cpp_web_programming.htm
Thanks
your question is a bit confusing, and without any sample of your code it is a bit unclear of what you want to do. however, the best suggestion i can give is to do this:
Store the text document on a server of your choice.
write a program to contact the server and download the data. (Using Winsock.h)
OR
Directly send the file to the computer. you'll have to write a program to contact the server at which point B is located.
for information on writing an application using Winsock.h, check here:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms737629(v=vs.85).aspx
if you really must store the data live in a web browser, then take a look at Java or VisualBasic, as both are heavily supported in all web browsers, while C++ is not.
Let me see if I understand you correctly. You want to send success / failure of the webserver to your client program?
Well, that's part of the job of a webserver, as dictated by the http protocol. A webserver will respond to a client request with a response header, followed by the requested page (if it exists as a valid resource on the server).
For more information on http response headers have a look at this article, or this wikipedia page, which both detail the request / response conversation between browser and webserver.
Hope this helps.
this might be a dumb question...
I wrote a C++ client program that communicates with a web service over HTTPS with the help of the cURL library.
I am wondering if the person using the client can see clearly the traffic originating from his computer using some sniffing program?
Or would he see encrypted data?
Thanks!
Using a utility like netcat to sniff data on the wire, the user would only see encrypted data. The only way to see the raw data is to log it inside the app, before it's passed to cURL, OR to find it in the machine's active RAM (much more difficult since it's likely to be fragmented).
Not if your app checks for valid certificates.
If your users have the ability to use a proxy server with your app, they could use fiddler's decrypt https sessions function to do this, but it results in an invalid certificate which could be made to stop it from working when detected.
He would see the encrypted data. Sniffers only see the packets, so if HTTPS is working as it should, the packets should be encrypted, and that's all the program could see.
If you would like to try it yourself, learn about ettercap-ng.
I doubt that an average user would be able to do that...
BUT there are ways to do this like:
replacing the cURL library with a proxy (if you link dynamically)
running your program under a debugger and placing breakpoints on the cURL functions
replacing the cURL program with a proxy (if you use it as a commandline utility)
digging deep and diessecting the memory at runtime
From my POV it is improbable (since you need some skill + knowledge + some control over the client environment to pull that off) but possible...
The SSL/TLS protocol is typically implemented at the application layer, so the data is encrypted before it is sent.
If the user has access to the certificate key(s) used to encrypt/decrypt the data, then he/she can plug them into WireShark and it can then decode sniffed HTTPS packets off the wire.
So I've been playing around with some simple HTML forwarding with c++. Haven't accomplished much and I have some questions on the backbone.
First: Do I need to use any special libraries other than socket libraries to simply forward HTML data and connections?
Second: When a client connects to an HTML server, is the TCP connection kept open? Or is it closed once data is sent?
Third: When I forward data, from a client to the server, the packet includes the destination address. I should technically be able to read this address and connect to the server via port 80, keep it open, and send and receive on that newly opened port right? Is there anything I have to do? Any time constraints? If I directly forward every single packet directly between the client and server the website should show up correctly on the client, correct?
I would prefer to keep any external libs to a minimum. But if necessary I can expand the program to include any required libraries.
So far I've gotten data to and from both parties, however the website does not function.
[platform] :: windows.primary && posix_compliant.secondary
First: No you do not need other special libraries but not using any that are available would to some extent be reinventing the wheel.
Second: No, HTTP is a connectionless protocol.
Third: An HTTP session begins with a request header, which in your case sounds like a POST. A POST may take more than one package, during which time the connection remains open. The server may well time you out.
You might look at libCURL even if you do not intend using it. (The source for that is in C, and is rather monolithic but it is commonly used).
After doing quite a bit of research, the greatest help I've had in my endeavors has been this website.
This one also helped quite a bit.
LibCURL is certainly the way to go. It's kind of dated, and everything is in C, but it's much easier than redoing everything..
quote from second site:
Like most network protocols, HTTP uses the client-server model: An HTTP client opens a connection and sends a request message to an HTTP server; the server then returns a response message, usually containing the resource that was requested. After delivering the response, the server closes the connection (making HTTP a stateless protocol, i.e. not maintaining any connection information between transactions).
I know that we can retrieve a webpage content through curl http://curl.haxx.se/ but is there any native way to retrieve the content of an webpage using c++ without using any library?
You will always need some kind of library in order to establish a network connection (I count OS APIs as libraries). That aside, you would have to:
establish a connection to the server
send a http request
receive and handle the http response
You can implement these steps by hand, but that really is a pain, especially because http is quite a complex protocol (even if you only implement the stuff you actually use, enough remains).
If you use Windows, you can use functions below
InternetOpen() - Initializes an application's use of the WinINet functions.
http://msdn.microsoft.com/en-us/library/aa385096(VS.85).aspx
InternetOpenUrl() - Opens a resource specified by a complete FTP, Gopher, or HTTP URL.
http://msdn.microsoft.com/en-us/library/aa385098(VS.85).aspx
InternetReadFile() - Reads data from a handle opened by the InternetOpenUrl
http://msdn.microsoft.com/en-us/library/aa385103(VS.85).aspx
InternetCloseHandle() - Closes a single Internet handle
http://msdn.microsoft.com/en-us/library/aa384350(VS.85).aspx
Hope it helps
PS: or you can use a more convenient function
URLDownloadToFile() - Downloads bits from the Internet and saves them to a file.
http://msdn.microsoft.com/en-us/library/ms775123(v=vs.85).aspx
Please tell me is it possile to know when a program is trying to download a file ( like in Internet Download Manager ). I want to catch that event (hook it), get the download url, and then destroy the event.
Thanks in advance..
#Jerry Coffin:Sr, I forgot to tell you that this feature of IDM is not active by default. It is only turned on when you enable the "Use advance browser integration" option at "Download/Options" of IDM menu.
Like here :
http://files.myopera.com/UenX/files/Detect.jpg
+ Check the (1) options, OK, then reboot.
+ After reboot, the (2) option will appear, check it, OK, and now run your software. You should see some thing likes (3)
( this appear when I run the msgr9us.exe ( Yahoo! Messenger setup file) )
Give it a try..
For a specific program such as Internet Explorer, doing this is quite reasonable (IE includes hooks to invoke your code under the right circumstances). For most programs it's not possible though -- they simply don't generate any "event" for you to hook and "destroy".
To make a long story short, to get anywhere with this, you'll almost certainly need to handle the situation on a case-by-base basis, writing code specific to each application you want to deal with -- and know that any other application and even newer versions of the applications you've dealt with will probably break what you're trying to do.
Not really. Consider how a browser typically downloads a file: it opens a TCP socket connection to a remote server, either on port 23 or 80, and using the FTP protocol or HTTP protocol on that connection. These things you can detect, intercept and modify with high reliability. But there are other programs that use other mthods. for instance, P2P filesharing programs such as BitTorrent do not use HTTP or FTP, nor do they download a file from a single server.
So, while you don't need to understand every program, you must be able to detect and understand every file download protocol instead.
you could hook the network stream and filter for http download requests.
you'll need some library to capture network traffic (e.g. http://en.wikipedia.org/wiki/Pcap).
Then you'll have to parse the network packets for the appropriate HTTP messages (sorry, I can't give them to you, I don't know them). I don't know if you can actually prevent packets from being sent though.
Another (easier) way would be to implement a proxy server (or modify an existing one) to do what you want. Then you just have to connect the IE to your proxy using the proxy server settings. Check for example Privoxy, which already does some kind of filtering.