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npcap-0.991 dotnet p/invoke with sharppcap #1692

cbwang505 opened this issue Aug 14, 2019 · 1 comment


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commented Aug 14, 2019

my operation system is win10 1903 x64,i uninstall npcap-0.9982,then install npcap-0.991, if i use the flowing p/invoke code, call the pcap_findalldevs function is in the class named SafeNativeMethods

 result = SafeNativeMethods.pcap_findalldevs(ref devicePtr,

the return devicePtr alway be IntPtr.Zero,this makes a error
then i move SafeNativeMethods.pcap_findalldev function method to the same class where i call that,like this following code

[DllImport(SafeNativeMethods.PCAP_DLL, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]		
		private static extern int pcap_findalldevs(ref IntPtr devicelist,
			StringBuilder errbuf);
	private static List<WinPcapDevice> Devices(string rpcapString,
			RemoteAuthentication remoteAuthentication)
			var retval = new List<WinPcapDevice>();
			IntPtr devicePtr=IntPtr.Zero ;
			StringBuilder errorBuffer = new StringBuilder(Pcap.PCAP_ERRBUF_SIZE); 			
			int result = pcap_findalldevs(ref devicePtr,

it works allright with no error,and devicePtr return is not IntPtr.Zero ,this flowing code run successfully
but i still caught a error when i start the same exe in iis like this

Process   _guardProcess = new Process();
				_guardProcess.StartInfo.CreateNoWindow = true;
				_guardProcess.StartInfo.UseShellExecute = false;
				_guardProcess.StartInfo.WorkingDirectory = ConfigurationManager.AppSettings["PeachRoot"];
				_guardProcess.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
				_guardProcess.StartInfo.LoadUserProfile = true;
				string tid = DateTime.Now.Ticks.ToString();
				_guardProcess.StartInfo.Arguments = tid;
				_guardProcess.StartInfo.FileName =	

the exe in run in no gui window ,till in run to this code pcap_findalldevs , this devicePtr return is IntPtr.Zero agin
i do not known is there some thing error with p/invoke or iis config or wpcap.dll


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commented Sep 18, 2019

@cbwang505 does this reproduce with the latest npcap release without installing winpcap compatibility api?

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