Reset Network Connections

Question

What's the best way to reset network connections using C#/.NET?

My company has several machines out with customers that connect by various means (3G, wifi, ethernet cable) and sometimes (especially with 3G) are reporting to Windows that they're still connected when they're not. I have a way to check if the connection is really live, but I'm struggling to reset them. Here's one problem:

var searcher = new ManagementObjectSearcher("select * from Win32_NetworkAdapter");
var managementObject = searcher.Get();
foreach (ManagementObject obj in managementObject)
{
    var name = obj.Properties["Name"].Value.ToString();
    Console.WriteLine(name);
    obj.InvokeMethod("Disable", null);
    obj.InvokeMethod("Enable", null);
}

As you can see, that will go through ALL network adapters and reset them, which I don't want to do. Furthermore, some adapters won't accept the null parameter.

I can get the NetworkInterface objects I want with this:

var interfaces = NetworkInterface.GetAllNetworkInterfaces().Where(ni => ni.IsReceiveOnly == false && 
            ni.OperationalStatus == OperationalStatus.Up && ni.NetworkInterfaceType != NetworkInterfaceType.Loopback);

But the NetworkInterface class seems to have no Start(), Stop(), Reset() etc methods. Where do I go from here?

score 3 · Accepted Answer · edited Jun 26 '16 at 20:51

After some searching and experimentation, I found this blog post:
Disable/Enable Network Connections Under Vista

It is a much better approach.

The just of it, is to use a utility called mgmtclassgen.exe to generate a wrapper class around the WMI Win32_NetworkAdapter class. Use the following command in a developer command prompt at the folder of your choosing:

mgmtclassgen Win32_NetworkAdapter -p NetworkAdapter.cs

After you've generated NetworkAdapter.cs you can import it into a new project, add System.Management.dll to your project references, and use the following code to disable or enable an adapter of your choosing:

SelectQuery query = new SelectQuery("Win32_NetworkAdapter", "NetConnectionStatus=2");
ManagementObjectSearcher search = new ManagementObjectSearcher(query);
foreach(ManagementObject result in search.Get())
{
    NetworkAdapter adapter = new NetworkAdapter(result);

    // Identify the adapter you wish to disable here. 
    // In particular, check the AdapterType and 
    // Description properties.

    // Here, we're selecting the LAN adapters.
    if (adapter.AdapterType.Equals("Ethernet 802.3")) 
    {
        adapter.Disable();
    }
}

Also keep in mind, your program will have to be run as an administrator on any systems where UAC is enabled - to do this it is recommended to create an application manifest. You can do that by changing the requestedExecutionLevel entry in your manifest file to this:

<requestedExecutionLevel level="requireAdministrator" uiAccess="false" />

I've imported the relevant data from that blog post into this answer, in case that blog post is no longer available in the future. This is standard practice here, please do it for any of your future answers. — caesay, Jun 26 '16 at 20:52

score 2 · Answer 2 · edited May 23 '17 at 11:58

2

Might be a bit simplistic, but could you call ipconfig /renew from a new process?

Process.Start("ipconfig", "/renew");

Alternatively, this similar question talks about using netsh, which I guess you could call from a process too How to disable (or reset) a network adapter programmatically in C#

edited May 23 '17 at 11:58

Community

1
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answered Aug 06 '13 at 08:58

owenrumney

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How confident are you with this? Will renewing an IP address fix a connection that's falsely reporting connected? – MrShoes Aug 06 '13 at 09:22
Well I've not tested it out if thats what you mean. My rationale is that if you release/renew the IP then you're going to be recycling the network interface. if you capture the exit code of the process it might give you an indication of if it successfully reset the adapter. Without repeating the issues you're having it would be difficult to catagorically state this will fix it – owenrumney Aug 06 '13 at 09:27

score 1 · Answer 3 · answered Aug 06 '13 at 09:51

You need Win32 API :

GetExtendedTcpTable : Get all exists tcp connection.
SetTcpEntry : Change tcp connection state.

Example code:

MIB_TCPROW row = new MIB_TCPROW();
row.dwState = TcpState.DeleteTcb;
row.dwLocalAddr = ...;
row.dwLocalPort = ...;
row.dwRemoteAddr = ...;
row.dwRemotePort = ...;
SetTcpEntry(ref row);

Reset Network Connections

3 Answers3