How to check for internet availability in c++

Question

I wrote one small function to check internet connection availability

void cis()
{
    if(InternetCheckConnection(NULL,FLAG_ICC_FORCE_CONNECTION,0))
    {
        cout << "internet alive";
    }
}

I'm using WinInet.h for InternetCheckConnection(). Now the problem is that I get the following linker error:

[Linker error] undefined reference to `_imp__InternetCheckConnectionA@12'

I am using DevC++ for my project. Any ideas on how to fix this linker problem or any other ideas to check for an active internet connection?

Did you check the [documentation[)http://msdn.microsoft.com/en-us/library/windows/desktop/aa384346%28v=vs.85%29.aspx) for the function you're calling? The "requirements" section lists this little piece of information: `Library: Wininet.lib`. By the way, congratulations on having found the single worst, buggiest and most outdated IDE possible. How is it even *possible* to end up using Dev-C++? That thing is *ancient* and even when it wasn't, it *sucked* — jalf, Jan 21 '13 at 07:35
Please excuse, but your posting is a mess. Even if you are not a native english speaker it should at least be possible to format your source properly, to start sentences with capitals and to finish them using a full-stop. — alk, Jan 21 '13 at 07:40
@jalf i used overall dev c++ , its now updated .... also anyother good IDE u wana suggest :) but do not suggest microsfot studio :D — darkworks, Jan 21 '13 at 07:44
@darkworks there are express versions of Visual Studio which are very powerful. Would you mind giving the reason why you don't want to use that? — default, Jan 21 '13 at 07:52
@jalf i have problems with compiling , linking like that with microsoft products , — darkworks, Jan 21 '13 at 07:59
@jalf well lets try , i have visual stduio 2012 , let see what happen when i copy my code to it — darkworks, Jan 21 '13 at 08:00
@jalf well i created console application project in visual studio under vc++ tab i press run button it gives error on its pre added coded that fatal error C1083: Cannot open include file: 'SDKDDKVer.h': No such file or directory i have not added code yet its pre coded when creating project — darkworks, Jan 21 '13 at 08:04
@jalf i have visual studio 2012 ultimate edition , so tell na how to fix this SDKDDVer.h problem — darkworks, Jan 21 '13 at 08:11
@darkworks which project type did you create? Make sure to select Win32 Console Application, and then from the Wizard that pops up, select `Empty project` to get rid of all the Microsoft cruft. Yes, Visual Studio has horrible project defaults. — jalf, Jan 21 '13 at 09:33
@jalf ok tell one thing more where can i did my libraries i mean .h file in dev c we place in /include folder , also libs in /libs folder so what about libs in visual studio too — darkworks, Jan 21 '13 at 10:04
I don't understand the question. Where can you *what* with libraries? Where you can find them? Where you should place them? Something else? — jalf, Jan 21 '13 at 11:35
@jalf ya i want to know in visual studio how can we add libraires (.h files) and libs (.a files ) i mean their folders location where they can be placed , in dev c++ normally the paths for header files are /include folder and for lib ./libs — darkworks, Jan 21 '13 at 12:34
@darkworks: you can place them wherever you like, but this one is already available with the Windows SDK (and, as far as I know, also with VS Express). Just open project properties and specify the library under linker inputs — jalf, Jan 21 '13 at 13:45
`#pragma comment(lib, "wininet.lib")` and `if (!InternetCheckConnectionW(L"http://google.com", FLAG_ICC_FORCE_CONNECTION, 0))` this good works ) — GooliveR, Jul 30 '17 at 15:36

score 5 · Accepted Answer · answered Jan 21 '13 at 07:36

5

Its a linker error. as per the documentation you need to use wininet library. adding -lwininet in makefile may work.

answered Jan 21 '13 at 07:36

Neel Basu

12,638
12
82
146

@darkworks: You can mark an answer as accepted b clicking the white checkmark on the left. – Niklas R Jan 21 '13 at 07:43
ya i will accept but say wait .... minutes :D – darkworks Jan 21 '13 at 07:47
The reason for that forced wait is that you often get multiple answers if you wait a bit, and then you can accept the best of them. Whereas if you accept an answer immediately, that typically discourages others from answering, so you might get poorer answers overall. – jalf Jan 21 '13 at 09:35
where to add -lwininet option in Visual Studio 2013? – Veena Dec 25 '15 at 18:52

score 2 · Answer 2 · answered Jan 21 '13 at 07:49

2

For unix

    if (system("ping www.google.com -c 2 > /dev/nul") == 0) {
    cout << "all good" << endl;
}else{
    cout << "bad" << endl;
}

Windows

    if (system("ping www.google.com -t 2 > nul") == 0) {
    cout << "all good" << endl;
}else{
    cout << "bad" << endl;
}

answered Jan 21 '13 at 07:49

Alexandru Calin

220
2
11

1

ya but some isp have blocked ping commmand , like in school u cant ping google.com – darkworks Jan 21 '13 at 07:58
True; it's good you found a solution thou! – Alexandru Calin Jan 21 '13 at 08:00

score 0 · Answer 3 · answered Jan 21 '13 at 07:40

0

It found your header, however you need to link to the libraries. Try adding Wininet.lib to your project(try as a file or in the linker properties) and make sure that the Windows SDK is properly installed on your system.

answered Jan 21 '13 at 07:40

MagikWorx

342
1
10

How to check for internet availability in c++

3 Answers3