Question

这是一个奇怪的请求。

我有一个字节数组，我需要通过串口发送到另一个使用C＃的设备。但是我需要首先在udp数据包中包装字节数组，但同样，它将通过串行端口发送，而不是通过udp发送。有没有办法构建一个udp数据包作为一个字节数组，然后通过串口发送？

我之前使用udp发送和接收过消息，但从未在udp数据包构建的地方发送，但是没有通过udp发送。

Answer 1

Answer 2

我将接受Yochai的回答，因为该链接（以及该站点内的其他页面）提供了构建udp数据包和ip头的代码。对于其他试图完成它的人来说，这里是代码：

如何称呼它：

var udpPacketBytes = UDPPacket.Construct(IPAddress.Parse("1.1.1.1"), 1000, IPAddress.Parse("2.2.2.2"), 6100, payloadBytes);

UDPPacket类：

public static class UDPPacket
    {
        public static byte[] Construct(IPAddress sourceAddress, ushort sourcePort, IPAddress destinationAddress, ushort destinationPort, byte[] payload)
        {
            var bindAddress = IPAddress.Any;

            // Make sure parameters are consistent
            //if ((sourceAddress.AddressFamily != destinationAddress.AddressFamily) || (sourceAddress.AddressFamily != bindAddress.AddressFamily))
            //{
            //    throw new Exception("Source and destination address families don't match!");
            //}

            // Start building the headers
            byte[] builtPacket;
            UdpHeader udpPacket = new UdpHeader();
            ArrayList headerList = new ArrayList();
            //Socket rawSocket = null;
            //SocketOptionLevel socketLevel = SocketOptionLevel.IP;

            // Fill out the UDP header first
            Console.WriteLine("Filling out the UDP header...");
            udpPacket.SourcePort = sourcePort;
            udpPacket.DestinationPort = destinationPort;
            udpPacket.Length = (ushort)(UdpHeader.UdpHeaderLength + payload.Length);
            udpPacket.Checksum = 0;

            if (sourceAddress.AddressFamily == AddressFamily.InterNetwork)
            {
                Ipv4Header ipv4Packet = new Ipv4Header();

                // Build the IPv4 header
                Console.WriteLine("Building the IPv4 header...");
                ipv4Packet.Version = 4;
                ipv4Packet.Protocol = (byte)ProtocolType.Udp;
                ipv4Packet.Ttl = 2;
                ipv4Packet.Offset = 0;
                ipv4Packet.Length = (byte)Ipv4Header.Ipv4HeaderLength;
                ipv4Packet.TotalLength = (ushort)System.Convert.ToUInt16(Ipv4Header.Ipv4HeaderLength + UdpHeader.UdpHeaderLength + payload.Length);
                ipv4Packet.SourceAddress = sourceAddress;
                ipv4Packet.DestinationAddress = destinationAddress;

                // Set the IPv4 header in the UDP header since it is required to calculate the
                //    pseudo header checksum
                Console.WriteLine("Setting the IPv4 header for pseudo header checksum...");
                udpPacket.ipv4PacketHeader = ipv4Packet;

                // Add IPv4 header to list of headers -- headers should be added in th order
                //    they appear in the packet (i.e. IP first then UDP)
                Console.WriteLine("Adding the IPv4 header to the list of header, encapsulating packet...");
                headerList.Add(ipv4Packet);
                //socketLevel = SocketOptionLevel.IP;
            }
            else if (sourceAddress.AddressFamily == AddressFamily.InterNetworkV6)
            {
                Ipv6Header ipv6Packet = new Ipv6Header();

                // Build the IPv6 header
                Console.WriteLine("Building the IPv6 header...");
                ipv6Packet.Version = 6;
                ipv6Packet.TrafficClass = 1;
                ipv6Packet.Flow = 2;
                ipv6Packet.HopLimit = 2;
                ipv6Packet.NextHeader = (byte)ProtocolType.Udp;
                ipv6Packet.PayloadLength = (ushort)(UdpHeader.UdpHeaderLength + payload.Length);
                ipv6Packet.SourceAddress = sourceAddress;
                ipv6Packet.DestinationAddress = destinationAddress;

                // Set the IPv6 header in the UDP header since it is required to calculate the
                //    pseudo header checksum
                Console.WriteLine("Setting the IPv6 header for pseudo header checksum...");
                udpPacket.ipv6PacketHeader = ipv6Packet;

                // Add the IPv6 header to the list of headers - headers should be added in the order
                //    they appear in the packet (i.e. IP first then UDP)
                Console.WriteLine("Adding the IPv6 header to the list of header, encapsulating packet...");
                headerList.Add(ipv6Packet);
                //socketLevel = SocketOptionLevel.IPv6;
            }

            // Add the UDP header to list of headers after the IP header has been added
            Console.WriteLine("Adding the UDP header to the list of header, after IP header...");
            headerList.Add(udpPacket);

            // Convert the header classes into the binary on-the-wire representation
            Console.WriteLine("Converting the header classes into the binary...");
            builtPacket = udpPacket.BuildPacket(headerList, payload);

            /*
            // Create the raw socket for this packet
            Console.WriteLine("Creating the raw socket using Socket()...");
            rawSocket = new Socket(sourceAddress.AddressFamily, SocketType.Raw, ProtocolType.Udp);

            // Bind the socket to the interface specified
            Console.WriteLine("Binding the socket to the specified interface using Bind()...");
            rawSocket.Bind(new IPEndPoint(bindAddress, 0));

            // Set the HeaderIncluded option since we include the IP header
            Console.WriteLine("Setting the HeaderIncluded option for IP header...");
            rawSocket.SetSocketOption(socketLevel, SocketOptionName.HeaderIncluded, 1);

            try
            {
                // Send the packet!
                Console.WriteLine("Sending the packet...");
                int rc = rawSocket.SendTo(builtPacket, new IPEndPoint(destinationAddress, destinationPort));
                Console.WriteLine("send {0} bytes to {1}", rc, destinationAddress.ToString());
            }
            catch (SocketException err)
            {
                Console.WriteLine("Socket error occurred: {0}", err.Message);
                // http://msdn.microsoft.com/en-us/library/ms740668.aspx
            }
            finally
            {
                // Close the socket
                Console.WriteLine("Closing the socket...");
                rawSocket.Close();
            }
            */

            return builtPacket;
        }
    }

协议类:(在此发布的时间太长）

Protocol Class Code

Answer 3

您应该通过创建一个包含标准UDP数据包中包含的所有数据的UDP类来构建您的UDP数据包。

数据为follows：

源端口[SP]（16位）：尝试连接或进行连接时，指定本地计算机正在等待侦听来自目标计算机的响应的端口。

目标端口[DP]（16位）：当用户希望连接到远程计算机上的服务时，应用层程序指定应使用哪些端口初始连接。当不作为初始连接的一部分时，它指定当数据包被发送到其目的地时将用于远程机器的端口号。

长度[Len]（16位）：这允许接收站知道有多少输入比特应该是有效数据包的一部分。长度是计算UDP包的一部分字节数，包括标头中的字节数。由于UDP总是在报头中有4个字段，每个字段有16位，而且数据/有效负载的长度可变，我们知道长度为8 +（有效载荷中的字节数）。

UDP校验和[UDPCS]（16位）：这是一个校验和，它覆盖UDP数据包的标头和数据部分，以允许接收主机验证传入UDP数据包的完整性。 UDP数据包在校验和字段中加载预定义的数字，然后在计算校验和时，校验和将写入先前的值。当数据包到达目的地时，目标机器的OS查找4头字段（从第16到31位产生的字节）并将它们从数据包中拉出，然后在校验和字段中没有任何内容的情况下重新计算数据包上的校验和。然后，OS将计算出的校验和与在数据包中传输的校验和进行比较。如果校验和相同，则数据正常，并且允许传递，但如果存在差异，则丢弃UDP数据包和数据，并且接收机器不会尝试获取新数据复制，发送机器不会尝试发送相同的数据包。数据包永远丢失。 UDP不可靠！有关可靠的传输层TCP / IP套件协议，请参阅TCP数据包。

数据（可变位）：正如您所料，这是UDP数据包的有效负载或数据部分。有效载荷可以是任何数量的协议（通常是应用层）。一些最常用的UDP协议包括NFS，DNS，以及多个音频和视频流协议。如果UDP数据包中发生错误并且需要修复错误，则由应用程序层查找错误并请求其应用程序层“数据块”或“数据块”。

创建一个包含所有这些数据的类并适当地填充它，重载ToString以允许您转换为Byte数组。

希望这有帮助。

Answer 4

我认为我在.NET中UdpClient没有看到任何实际的数据包级别类的原因是因为它很简单，因为它是无连接/无状态协议。

The packet format is crazy simple

bits             0 – 15                   16 – 31
        +-----------------------+-------------------------+
0       | Source Port Number    | Destination Port Number |
        +-----------------------+-------------------------+
32      | Length                | Checksum                |
        +-----------------------+-------------------------+
64      |                                                 |
        |                      Data                       |
        |                                                 |
        +-------------------------------------------------+

Also, do note that the checksum computation does actually have a little bit of complexity to it

如何构造UDP数据包但不发送它

4 个答案: