如何检测到计算机是否online,offline

[edwardyi]

如何检测到计算机是否online,offline

[BareHead]

用windows socket api,在两台计算机间建立tcp/ip的socket连接,就可以检测online还是offline了

[Lin]

向指定计算机发ICMP包，看有否回应。

[WHQ]

InternetGetConnectedState/InternetGetConnectedStateEx

[kxy]

用PING
www.midatech.com/kxy有ping的soure (VC的)

[tide]

可以检测注册表。具体键值忘了，可以用regmon监视一下。

[softdoctor]

使用API 函数 InternetAttemptConnect
很容易的。
if(InternetAttemptConnect(0)==ERROR_SUCCESS)
{
// 在线
}
else
{
//离线
}

[edwardyi]

please introduce it in detail

[edwardyi]

我想写一个上网记费软件，能否更详细的说明

[olo]

我也想知道局域网怎么办。

[edwardyi]

为何我用RasEnumConnections，InternetAttemptConnect等函数
时总是报错（undefined identifier),是需要包什头文件呢，还是缺少dll?另外请教怎样调出windows下的拨号对话框？谢谢各位的鼎立帮助！

[SoftDIY]

贴上一篇msdn的howto，url是http://support.microsoft.com/support/kb/articles/Q242/5/58.ASP

HOWTO: Detecting If You Have a Connection to the Internet

--------------------------------------------------------------------------------
The information in this article applies to:

Microsoft Internet Explorer (Programming) versions 4.0, 4.01, 4.01 SP1, 4.01 SP2, 5

--------------------------------------------------------------------------------


SUMMARY
Many of you want to know if a computer has an active Internet connection before trying to connect to the Internet using the WinInet API or some other communication interface. The internet connection is important if you don't want your application to cause Windows to automatically dial the default Internet modem connection.

This article provides a mechanism for determining if an Internet site is accessible without the risk of you being prompted to dial into another Internet Service Provider.



MORE INFORMATION
Usually the best way to determine if you have a connection to a particular computer is to attempt the connection. If the autodial feature of Windows is enabled then attempting the connection may cause the default Internet dialup connectoid to be opened, and you will be prompted with your credentials to connect.

To avoid having the default Internet connectoid dialed, the InternetGetConnectedState function can be used to determine if there is a default Internet dialup connectoid configured and whether it is currently active or not. If there is a default Internet dialup connectoid configured and it is not currently active then InternetGetConnectedState will return FALSE. If InternetGetConnectedState returns TRUE then you can attempt to connect to the Internet resource without fear of being prompted to connect to another Internet Service Provider.

The following code demonstrates how you would do this:


if (InternetGetConnectedState(...) == FALSE)
{
// Don't attempt connection or it will bring up the dialog
...
}
else
{
//Attempt connection
if (InternetOpenURL(...) == NULL)
{
// Call failed
err = GetLastError();
if ((err == ERROR_INTERNET_NAME_NOT_RESOLVED) and and
(err == ERROR_INTERNET_CANNOT_CONNECT) and and
(err == ERROR_INTERNET_TIMEOUT))
{
// probably not connected...handle appropriately
...
}
}
// We're connected!!!
....
}


You cannot rely solely on the fact that InternetGetConnectedState returning TRUE means that you have a valid active Internet connection. It is impossible for InternetGetConnectedState to determine if the entire connection to the Internet is functioning without sending a request to a server. This is why you need to send a request to determine if you are really connected or not. You can be assured however that if InternetGetConnectedState returns TRUE, that attempting your connection will NOT cause you to be prompted to connect to the default Internet Service Provider.

Be aware that InternetGetConnectedState only reports the status of the default Internet connectoid on Internet Explorer 4.x. If a nondefault connectoid is connected, InternetGetConnectedState always returns FALSE (unless a LAN connection is used). With Internet Explorer 4.x configured to use a LAN connection, InternetGetCo nectedState always returns TRUE.

Internet Explorer 5 behaves differently. If you are currently dialed into a different dial-up in Internet Explorer 5, InternetGetConnectedState reports dial-up connection status as long as any connectoid is dialed or an active LAN connection exists.

There are some other ways to try to determine if you currently have a connection to a particular network resource. The IsDestinationReachable() function can be used to find out if there is a current connection to an address. However, he IsDestinationReachable() function is only concerned with whether the IP address is reachable from your computer. It does not work through HTTP proxies or firewalls that restrict ICMP ping packets.

It is also possible to use RasEnumConnections to enhance your code so that you can tell if there is an active dialup connection that might have Internet access even though it is not the default Internet dialup connectoid.

Additional query words:

Keywords : kbIE kbIE400 kbIE401sp1 kbIE401sp2 kbIE500 kbGrpInetServer kbDSupport kbIEFAQ
Version : WINDOWS:4.0,4.01,4.01 SP1,4.01 SP2,5
Platform : WINDOWS
Issue type : kbhowto

[SoftDIY]

关于no define error，请include相关头文件。ras函数同时还须input ras的lib文件
拨号对话框可以玩个虚的，InternetOpenURL就可以弹出缺省对话框

[SoftDIY]

既是上网记费软件，就是针对拨号用户了，try the code
BOOL CYouSApp::IsRASConnected() //code by softdiy
{
RASCONN rasconn;
DWORD dNumber,dSize ;
rasconn.dwSize = sizeof(RASCONN);
dSize = sizeof(rasconn);
if (RasEnumConnections(&rasconn,&dSize,&dNumber)!=0)
return false;
if (dNumber==0)
return false;
return true;
}

Softdoctor,InternetAttemptConnect只是监测ie是否选了脱机，没有在线监测

[Un1]

SoftDIY:
如果是通过局域网上网怎么办？