Question

我有一个项目，我正在尝试将序列化对象发送到服务器，然后等待“OK”或“ERROR”消息返回。

的海报有类似的问题

问题是，我似乎能够发送原始对象的唯一方法是关闭连接，但然后（当然）我迫不及待地想看看服务器是否成功处理了对象。 / p>

private void button4_Click(object sender, EventArgs e)
{
    RequestPacket req = new RequestPacket();

    /// ... Fill out request packet ...

    /// Connect to the SERVER to send the message...
    TcpClient Client = new TcpClient("localhost", 10287);
    using (NetworkStream ns = Client.GetStream())
    {
        XmlSerializer xml = new XmlSerializer(typeof(RequestPacket));
        xml.Serialize(ns, req);

        /// NOTE: This doesn't seem to do anything.... 
        ///       The server doesn't get the object I just serialized.
        ///       However, if I use ns.Close() it does... 
        ///          but then I can't get the response.
        ns.Flush();

        // Get the response. It should be "OK".
        ResponsePacket resp;

        XmlSerializer xml2 = new XmlSerializer(typeof(ResponsePacket));
        resp = (ResponsePacket)xml2.Deserialize(ns);


        /// ... EVALUATE RESPONSE ...
    }

    Client.Close()
}

更新：对一位评论者的回应，我认为客户不会有错。它只是在等待对象，对象永远不会出现，直到我关闭套接字....但是，如果我错了，我会公开吃掉乌鸦。 =）这是客户：

    static void Main(string[] args)
    {
        // Read the port from the command line, use 10287 for default
        CMD cmd = new CMD(args);
        int port = 10287;

        if (cmd.ContainsKey("p")) port = Convert.ToInt32(cmd["p"]);

        TcpListener l = new TcpListener(port);
        l.Start();

        while (true)
        {
            // Wait for a socket connection.
            TcpClient c = l.AcceptTcpClient();

            Thread T = new Thread(ProcessSocket);

            T.Start(c);
        }
    }


    static void ProcessSocket(object c)
    {
        TcpClient C = (TcpClient)c;

        try
        {
            RequestPacket rp;
            //// Handle the request here.
            using (NetworkStream ns = C.GetStream())
            {
                XmlSerializer xml = new XmlSerializer(typeof(RequestPacket));
                rp = (RequestPacket)xml.Deserialize(ns);
            }

            ProcessPacket(rp);
        }
        catch
        {
            // not much to do except ignore it and go on.
        }
    }

是的......就这么简单。

Answer 1

哦，你可以归咎于Nagle's algorithm。它与C＃无关，但它是TCP / IP堆栈的默认行为。使用NoDelay方法启用SetSocketOption套接字选项。但要小心，禁用Nagle的算法会降低吞吐量。

我也不确定你在套接字上使用的那个流，因为我根本不是C＃开发人员，但是尝试删除它的实例，所以它确实写了： - ）

Answer 2

短版本显然是在使用XmlSerializer（或任何其他大blob）将数据推送到NetworkStream时，它只会无限期地保持行打开，等待写入更多信息。它只会在关闭连接后刷新连接。这会产生一种情况，即此方法非常适合发送，但不能接收。或相反亦然。它变成了单向通信，对于通过同一连接继续来回通信毫无用处。

我不得不在表面上看起来如此优雅的东西上工作，但是回到我原来的C天，我首先使用发送“字节数”的数据包，然后是实际数据包。这使我能够在另一端读取确切的字节数，这样我就不会陷入阻塞模式。

为了简化我的生活，我创建了一个类，它包含一些静态方法，用于发送和接收。这个类可以在网络上发送任何XML可序列化的类，因此它可以完成我需要它做的事情。

如果有人有更优雅的解决方案，我会乐于听到它。

public class PacketTransit
{
    public static void SendPacket(TcpClient C, object Packet)
    {
        MemoryStream ms = new MemoryStream();
        XmlSerializer xml = new XmlSerializer(Packet.GetType());
        xml.Serialize(ms, Packet);
        ms.Position = 0;
        byte[] b = ms.GetBuffer();
        ms.Dispose();

        byte [] sizePacket = BitConverter.GetBytes(b.Length);
        // Send the 4-byte size packet first.
        C.Client.Send(sizePacket, sizePacket.Length, SocketFlags.None);
        C.Client.Send(b, b.Length, SocketFlags.None);
    }

    /// The string is the XML file that needs to be converted.
    public static string ReceivePacket(TcpClient C, Type PacketType)
    {
        byte [] FirstTen = new byte[1024];
        int size = 0;
        byte[] sizePacket = BitConverter.GetBytes(size);

        // Get the size packet
        int sp = C.Client.Receive(sizePacket, sizePacket.Length, SocketFlags.None);
        if (sp <= 0) return "";

        size = BitConverter.ToInt32(sizePacket, 0);

        // read until "size" is met
        StringBuilder sb = new StringBuilder();
        while (size > 0)
        {
            byte[] b = new byte[1024];
            int x = size;
            if (x > 1024) x = 1024;
            int r = C.Client.Receive(b, x, SocketFlags.None);
            size -= r;
            sb.Append(UTF8Encoding.UTF8.GetString(b));
        }

        return sb.ToString();
    }

    /// The XML data that needs to be converted back to the appropriate type.
    public static object Decode(string PacketData, Type PacketType)
    {
        MemoryStream ms = new MemoryStream(UTF8Encoding.UTF8.GetBytes(PacketData));
        XmlSerializer xml = new XmlSerializer(PacketType);
        object obj = xml.Deserialize(ms);
        ms.Dispose();

        return obj;
    }

    public static RequestPacket GetRequestPacket(TcpClient C)
    {
        string str = ReceivePacket(C, typeof(RequestPacket));

        if (str == "") return new RequestPacket();

        RequestPacket req = (RequestPacket) Decode(str, typeof(RequestPacket));

        return req;
    }

    public static ResponsePacket GetResponsePacket(TcpClient C)
    {
        string str = ReceivePacket(C, typeof(ResponsePacket));

        if (str == "") return new ResponsePacket();

        ResponsePacket res = (ResponsePacket)Decode(str, typeof(ResponsePacket));

        return res;
    }
}

要使用此类，我只需要调用PacketTransit.SendPacket(myTcpClient, SomePacket)来发送任何给定的XML-Serializable对象。然后，我可以使用PacketTransit.GetResponsePacket或PacketTransit.GetRequestPacket在另一端接收它。

对我来说，这项工作非常顺利，但它比原先预期的要多得多。

Answer 3

你应该使用链接到网络流的StreamWriter / Reader，.Flush在NetworkStream上什么也不做，请看这里：

http://www.c-sharpcorner.com/UploadFile/dottys/SocketProgDTRP11222005023030AM/SocketProgDTRP.aspx

Answer 4

我认为这里真正的问题可能是XmlDeserializer在从流中读取EOS之前可能不会返回。您可能需要关闭发送流以进行输出以强制执行此操作。

C＃为什么不“刷新”强制网络流中的字节？

4 个答案: