CODEWITHSUNDEEP
c#.netnetwork-programming
Xcelled
Xcelled

Reputation: 2104

Determine which network adapter a process is using

I've seen several similar questions on Google, but nothing exactly matches what I'm trying to do. I'm making a lag-reducing program (for a game) that basically lowers the user's MTU when a certain process is open, and restores it when the process is closed. However, MTU is a network-adapter specific setting, and some users have multiple connected network adapters. To this end, I thought it'd be nice to have the program also detect which adapter is being used by the game, and only change the MTU on that adapter.

The game will only use one adapter at a time.

I can't hardcode in end-server-IP addresses because they change fairly frequently. It seems to be there must be a way to determine which adapter the other process is using without knowing the end IP address, but I can't seem to find it.

EDIT: Thanks to Cicada and Remco, I've solved the problem.

I used the ManagedIPHelper class that Remco linked to (ManagedIpHelper) and Cicada's comments led me to this article (Identifying active network interface)

Combining those with some (Nasty, horribly unoptimized) LINQ, I got this code snippet, which takes the process name and returns the Network Interface it's using, or null if it can't find one.

    private NetworkInterface getAdapterUsedByProcess(string pName)
    {
        Process[] candidates = Process.GetProcessesByName(pName);
        if (candidates.Length == 0)
            throw new Exception("Cannot find any running processes with the name " + pName + ".exe");

        IPAddress localAddr = null;
        using (Process p = candidates[0])
        {
            TcpTable table = ManagedIpHelper.GetExtendedTcpTable(true);
            foreach (TcpRow r in table)
                if (r.ProcessId == p.Id)
                {
                    localAddr = r.LocalEndPoint.Address;
                    break;
                }
        }

        if (localAddr == null)
            throw new Exception("No routing information for " + pName + ".exe found.");

        foreach (NetworkInterface nic in NetworkInterface.GetAllNetworkInterfaces())
        {
            IPInterfaceProperties ipProps = nic.GetIPProperties();
            if (ipProps.UnicastAddresses.Any(new Func<UnicastIPAddressInformation, bool>((u) => { return u.Address.ToString() == localAddr.ToString(); })))
                return nic;
        }
        return null;
    }

Testing confirms this works perfectly! Many thanks, guys!

Side notes to anyone using this snippet:

Upvotes: 4

Views: 3932

Answers (1)

Remco
Remco

Reputation: 1933

in addition to Cicada, this must help you:

It is a C# wrapper around some c/c++ code, which gets you the list of all open connections with associated PID ( Process Id ).

http://www.timvw.be/2007/09/09/build-your-own-netstatexe-with-c/

I do believe this is the only way to go, determine the process(id) based on executable path/name and try to find the current connection of that process.

Upvotes: 2

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