我想用TCP協議做一些原始套接字編程,但是我遇到了PacketDotNet和TCP校驗和的問題。PacketDotNet問題與CalculateTCPChecksum,ValidTCPChecksum和ValidChecksum
我得到PacketDotNet.TCPPacket內的空指針異常。我得到的例外是:
ValidTCPChecksum = 'tcpPacket.ValidTCPChecksum' threw an exception of type 'System.NullReferenceException'
而且
System.NullReferenceException: Object reference not set to an instance of an object.
at PacketDotNet.TransportPacket.CalculateChecksum(TransportChecksumOption option)
at PacketDotNet.TcpPacket.CalculateTCPChecksum()
at ProjectServer.MainWindow.packetstuff(String toIp, String fromIp, Byte[] payload) in c:\\Users\\MyUser\\Documents\\Visual Studio 2012\\Projects\\ProjectServer\\ProjectServer\\MainWindow.xaml.cs:line 131
at ProjectServer.MainWindow.Project_Click(Object sender, RoutedEventArgs e) in c:\\Users\\MyUser\\Documents\\Visual Studio 2012\\Projects\\ProjectServer\\ProjectServer\\MainWindow.xaml.cs:line 68
線131 tcpPacket.Checksum = (ushort)tcpPacket.CalculateTCPChecksum();
看來,因爲它可能有一些做HelpLink
是空的,但我不是100 %肯定。
我試圖做自己的校驗和,但我迄今還沒有能夠實現工作校驗和算法。
這裏是基本構建我的數據包的packetstuff方法。也許它有什麼問題。
public void packetstuff(string toIp, string fromIp, byte[] payload)
{
ushort tcpSourcePort = 123;
ushort tcpDestinationPort = 321;
var tcpPacket = new TcpPacket(tcpSourcePort, tcpDestinationPort);
var ipSourceAddress = System.Net.IPAddress.Parse(fromIp);
var ipDestinationAddress = System.Net.IPAddress.Parse(toIp);
var ipPacket = new IPv4Packet(ipSourceAddress, ipDestinationAddress);
var sourceHwAddress = "MY-MA-CA-DD-RE-SS";//?actually a bit unsure what this should be
var ethernetSourceHwAddress = System.Net.NetworkInformation.PhysicalAddress.Parse(sourceHwAddress);
var destinationHwAddress = "MY-MA-CA-DD-RE-SS";
var ethernetDestinationHwAddress = System.Net.NetworkInformation.PhysicalAddress.Parse(destinationHwAddress);
var ethernetPacket = new EthernetPacket(ethernetSourceHwAddress,
ethernetDestinationHwAddress,
EthernetPacketType.None);
if (tcpPacket != null)
{
tcpPacket.Checksum = 0;
tcpPacket.Checksum = (ushort)tcpPacket.CalculateTCPChecksum(); //This is where the error occurs.
}
ipPacket.PayloadPacket = tcpPacket;
ipPacket.UpdateIPChecksum();
ethernetPacket.PayloadPacket = ipPacket;
ethernetPacket.UpdateCalculatedValues();
packetBytes = ethernetPacket.Bytes;
Thread producer = new Thread(new ThreadStart(ThreadRun));
device.Open();
producer.Start();
}
Windows7中,VS2012
唉,我贊成[PcapDotNet(http://pcapdotnet.codeplex.com/),我開始工作,現在被遺棄packetDotNet。 – Automatico 2013-02-27 17:39:14