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Трипольский Пётр
Asked:2020-07-13 20:30:27 +0800 CST2020-07-13 20:30:27 +0800 CST

在 C# 中实现 WebSocket 协议

  • 772

GitHub 上有一个存储库，实现了 WebSocket 协议的解码帧。问题是如果同时发送多条消息，浏览器会粘住帧，代码就不能正常工作。

private String DecodeMessageFromClient(Byte[] bytes)
{
    try
    {
        String incomingData = String.Empty;
        Byte secondByte = bytes[1];

        Int32 dataLength = secondByte & 127;
        Int32 indexFirstMask = 2;

        if (dataLength == 126) indexFirstMask = 4;
        else if (dataLength == 127) indexFirstMask = 10;

        IEnumerable<Byte> keys = bytes.Skip(indexFirstMask).Take(4);
        Int32 indexFirstDataByte = indexFirstMask + 4;

        Byte[] decoded = new Byte[bytes.Length - indexFirstDataByte];
        for (Int32 i = indexFirstDataByte, j = 0; i < bytes.Length; i++, j++)
        {
            decoded[j] = (Byte)(bytes[i] ^ keys.ElementAt(j % 4));
        }

        return incomingData = Encoding.UTF8.GetString(decoded, 0, decoded.Length);
    }
    catch (Exception ex)
    {
        Debug.WriteLine("Could not decode due to :" + ex.Message);
    }
    return null;
}

在此处输入图像描述

根据变量的名称，发生这种情况是因为代码跳过了标头，并将其余信息视为帧的内容。但由于消息中有两帧，因此不会跳过第二个标头。

for (Int32 i = indexFirstDataByte, j = 0; i < bytes.Length; i++, j++)
c#

1 个回答

  1. Best Answer

    新代码更难。它接收一个字节数组，从那里选择第一帧并返回未参与解码的剩余字节

    public static byte[] WebSocketBackendMessage(this NetworkStream stream,byte[] bytes,out string message,out WebSocketMessageType type)
{
    byte oppcode = bytes[0];
    byte shift = 15;
    type = (WebSocketMessageType)(oppcode & shift);

    String incomingData = String.Empty;
    Byte secondByte = bytes[1];
    Int32 dataLength = secondByte & 127;
    Int32 indexFirstMask = 2;
    if (dataLength == 126)
    {
        indexFirstMask = 4;
        byte[] newlenght = bytes.Skip(2).Take(2).ToArray();
        Array.Reverse(newlenght);
        dataLength = BitConverter.ToUInt16(newlenght, 0);
    }
    else if (dataLength == 127)
    {
        indexFirstMask = 10;
        throw new Exception("Слишком большой массив информации был отправлен на вебсокет!");
    }
    IEnumerable<Byte> keys = bytes.Skip(indexFirstMask).Take(4);
    Int32 indexFirstDataByte = indexFirstMask + 4;

    Byte[] decoded = new Byte[bytes.Length - indexFirstDataByte];
    for (Int32 i = indexFirstDataByte, j = 0; i < indexFirstDataByte + dataLength; i++, j++)
    {
        decoded[j] = (Byte)(bytes[i] ^ keys.ElementAt(j % 4));
    }

    message = Encoding.UTF8.GetString(decoded, 0, decoded.Length);

    byte[] remain = bytes.Skip(indexFirstDataByte + dataLength).ToArray();
    if (remain.Length == 0) return null;
    else return remain;
}

    它是这样使用的：

    byte[] block = stream.ReadBlock();
string message = null;
WebSocketMessageType type;

bool lastFrameEmpty = false;
while(!lastFrameEmpty)
{
    lastFrameEmpty = (block = stream.WebSocketBackendMessage(block, out message,out type)) == null;
    if (type == WebSocketMessageType.Text)
    {
        Console.WriteLine("MESSAGE: {0}", message);
    }
    if (type == WebSocketMessageType.Close)
    {
        continueWorking = false;
        break;
    }
}

    以防万一，我将附上读取从浏览器接收到的信息块的扩展代码

    public static byte[] ReadBlock(this NetworkStream stream)
{
    Byte[] bytes = null;

    using (MemoryStream tmp = new MemoryStream())
    {
        byte[] data = new byte[1];
        int readed = -1;
        while (stream.DataAvailable)
        {
            readed = stream.Read(data, 0, data.Length);
            tmp.Write(data, 0, readed);
        }
        if (readed > -1)
        {
            bytes = tmp.ToArray();
        }
    }
    return bytes;
}

    您可以从以下链接下载 Visual Studio 的解决方案：https ://cloud.mail.ru/public/KEeF/H81Q22MXP

    • -1

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