topic Re: Check internet connection from Fortran program in Intel® Fortran Compiler

Check internet connection from Fortran program

SoniaG — Thu, 04 Feb 2021 03:32:50 GMT

I want my Fortran program to check for internet connection and warn the user if not connected. I think I need to use the method GetConnectivity but can't find an example of this for use in Fortran. Apparently the API, InternetGetConnectedState is no longer recommended.

Any help or advice would be appreciated - manys thanks in advance.

Re: Check internet connection from Fortran program

andrew_4619 — Thu, 04 Feb 2021 13:13:07 GMT

Not quite the same thing but I use URLDownloadToFile to download a page from the web to a local file. A failure to get something that is known to exist could be indicative of no connection.

Re: Check internet connection from Fortran program

jimdempseyatthecove — Thu, 04 Feb 2021 15:47:50 GMT

Experiment with EXECUTE_COMMAND_LINE with "ping -w 500 -n 1 yahoo.com>check.txt"

You should test to see if exitstat returns error code when ping fails, and in which case you need not check the check.txt for ping error.

Jim Dempsey

Re: Check internet connection from Fortran program

JohnNichols — Thu, 04 Feb 2021 15:59:27 GMT

https://community.intel.com/t5/Intel-Fortran-Compiler/Checking-internet-connection-from-fortran/td-p/813094

There is a rather interesting answer here from 2011 -- it should still work

Re: Check internet connection from Fortran program

SoniaG — Fri, 05 Feb 2021 06:12:37 GMT

Thanks @jimdempseyatthecove

I have written the following code but, although the command execution runs, I almost always get an estat of 1. My program is running in Windows and I am connected to the internet (it's a strong signal and not intermittant). I get similar results whether running in debug (Visual Studio) or in production.

If the code below looks ok, I assume there must be something else at play?

call execute_command_line("ping -w 500 -n 1 yahoo.com>check.txt",exitstat=estat,cmdstat=cstat,cmdmsg=cmsg)
if(cstat > 0) then
iret = messagebox(ghwndmain,'Command execution failed with error'//trim(cmsg)//char(0),'Check for internet connection'//char(0),mb_ok)
else if(cstat < 0) then
iret = messagebox(ghwndmain,'Command execution not supported'//trim(cmsg)//char(0),'Check for internet connection'//char(0),mb_ok)
else
write(cestat,'(I4)')estat
if(estat==0)then
iret = messagebox(ghwndmain,'Internet connection ok, estat ='//trim(cestat)//char(0),'Check for internet connection'//char(0),mb_ok)
else
iret = messagebox(ghwndmain,'No internet connection found, estat ='//trim(cestat)//char(0),'Check for internet connection'//char(0),mb_ok)
end if
end if

Re: Check internet connection from Fortran program

jimdempseyatthecove — Fri, 05 Feb 2021 13:19:48 GMT

What happens if you set the timeout to -w 5000?

Jim Dempsey

Re: Check internet connection from Fortran program

FortranFan — Fri, 05 Feb 2021 17:48:02 GMT

@SoniaG ,

Re: ".. I think I need to use the method GetConnectivity but can't find an example of this for use in Fortran. ..," you may have seen this at the Microsoft site:

https://docs.microsoft.com/en-us/windows/win32/api/netlistmgr/nf-netlistmgr-inetworklistmanager-getconnectivity

You'll notice the GetConnectivity - which is indeed Microsoft's recommended method in their so-called unmanaged programs (and which is what all Fortran apps are) on Windows - is a C++ class method of INetworkListManager that is invokable via COM. As such, you would either need to use Intel Fortran's COM interoperability module(s) or setup something yourself using C-Fortran interoperability. Both are a little more effort than I would be willing to undertake, so I would instead write a small extern "C" wrapper function in C++ like so: it's a one-time effort easier to manage I feel:

#include <stdio.h> #include <tchar.h> #include <Windows.h> #include <Netlistmgr.h> #include <atlbase.h> extern "C" int IsConnected(char *msg, size_t lenmsg) { int irc = 0; CoInitialize(NULL); { CComPtr<INetworkListManager> pNLM; HRESULT hr = CoCreateInstance(CLSID_NetworkListManager, NULL, CLSCTX_ALL, __uuidof(INetworkListManager), (LPVOID*)&pNLM); if (SUCCEEDED(hr)) { NLM_CONNECTIVITY con = NLM_CONNECTIVITY_DISCONNECTED; hr = pNLM->GetConnectivity(&con); if SUCCEEDED(hr) { if (con & NLM_CONNECTIVITY_DISCONNECTED) snprintf(msg, lenmsg, "%s\n", "Disconnected"); if (con & NLM_CONNECTIVITY_IPV4_NOTRAFFIC) snprintf(msg, lenmsg, "%s\n", "IP4: No Traffic"); if (con & NLM_CONNECTIVITY_IPV6_NOTRAFFIC) snprintf(msg, lenmsg, "%s\n", "IP6: No Traffic"); if (con & NLM_CONNECTIVITY_IPV4_INTERNET) snprintf(msg, lenmsg, "%s\n", "IP4: Internet"); if (con & NLM_CONNECTIVITY_IPV4_LOCALNETWORK) snprintf(msg, lenmsg, "%s\n", "IP4: Local"); if (con & NLM_CONNECTIVITY_IPV4_SUBNET) snprintf(msg, lenmsg, "%s\n", "IP4: Subnet"); if (con & NLM_CONNECTIVITY_IPV6_INTERNET) snprintf(msg, lenmsg, "%s\n", "IP6: Internet"); if (con & NLM_CONNECTIVITY_IPV6_LOCALNETWORK) snprintf(msg, lenmsg, "%s\n", "IP6: Local"); if (con & NLM_CONNECTIVITY_IPV6_SUBNET) snprintf(msg, lenmsg, "%s\n", "IP6: Subnet"); } } irc = (int)hr; } CoUninitialize(); return irc; }

And setup an interface to it in Fortran like so, again a one-time effort:

module NetListMgr_m use, intrinsic :: iso_c_binding, only : c_char, c_int, c_size_t interface function IsConnected( Msg, LenMsg ) result(r) bind(C, name="IsConnected" ) ! int IsConnected(char *msg, size_t lenmsg); import :: c_char, c_int, c_size_t ! Argument list character(kind=c_char, len=1), intent(in) :: Msg(*) integer(c_size_t), intent(in), value :: LenMsg ! Function result integer(c_int) :: r end function end interface end module

Then the following Fortran test program can make use of it:

program TestConnection use, intrinsic :: iso_c_binding, only : c_char, c_size_t, c_int use NetListMgr_m, only : IsConnected character(kind=c_char, len=256) :: ConnectionState integer(c_size_t) :: lens integer(c_int) :: cstat lens = int( len(ConnectionState), kind=kind(lens) ) cstat = IsConnected( ConnectionState, lens ) print *, "ctsat: ", cstat print *, trim(ConnectionState) end program

You can tuck away the above C function and the Fortran module code in a library (static or DLL) and use it in your Fortran programs - Visual Studio projects can make this easy as you may know.

From the command-line, for illustration purposes, you can expect the following behavior:

C:\Temp>cl /c /EHsc /W3 IsConnected.cpp Microsoft (R) C/C++ Optimizing Compiler Version 19.26.28806 for x64 Copyright (C) Microsoft Corporation. All rights reserved. IsConnected.cpp C:\Temp>ifort /c /standard-semantics /warn:all /stand:f18 NetListMgr.f90 Intel(R) Fortran Intel(R) 64 Compiler Classic for applications running on Intel(R) 64, Version 2021.1.2 Build 20201208_000000 Copyright (C) 1985-2020 Intel Corporation. All rights reserved. C:\Temp>ifort /c /standard-semantics /warn:all /stand:f18 TestConnection.f90 Intel(R) Fortran Intel(R) 64 Compiler Classic for applications running on Intel(R) 64, Version 2021.1.2 Build 20201208_000000 Copyright (C) 1985-2020 Intel Corporation. All rights reserved. C:\Temp>link TestConnection.obj NetListMgr.obj IsConnected.obj /subsystem:console /out:TestConnection.exe Microsoft (R) Incremental Linker Version 14.26.28806.0 Copyright (C) Microsoft Corporation. All rights reserved. C:\Temp>TestConnection.exe ctsat: 0 IP4: Internet C:\Temp>

P.S.> Some of the above code is a bit more verbose than otherwise, but it's for the benefit of other readers also. Also, it's possible Intel Fortran provides some module procedures for this - I've not checked - but that will be compiler-specific. The above should work with any Fortran standard supporting compiler.

Re: Check internet connection from Fortran program

JohnNichols — Fri, 05 Feb 2021 18:09:15 GMT

Sonia:

FortranFan's method is as good as it gets, I would adopt this one and stop searching.