我正在尝试从我的网络服务器检索上传的文件。当客户端通过网络表单(随机文件)发送其文件时，我需要解析请求以获取文件并进一步处理它。 基本上，代码如下:

HttpListenerContext context = listener.GetContext();
HttpListenerRequest request = context.Request;
StreamReader r = new StreamReader(request.InputStream, System.Text.Encoding.Default);
// this is the retrieved file from streamreader
string file = null;

while ((line = r.ReadLine()) != null){
     // i read the stream till i retrieve the filename
     // get the file data out and break the loop 
}
// A byststream is created by converting the string,
Byte[] bytes = request.ContentEncoding.GetBytes(file);
MemoryStream mstream = new MemoryStream(bytes);

// do the rest

因此，我能够检索文本文件，但对于所有其他文件，它们已损坏。 有人能告诉我如何正确解析这些 HttplistnerRequests(或提供轻量级替代方案)吗？

最佳答案

我认为你用 HttpListener 做这件事会让你自己变得更难。而不是使用 ASP.Net 的内置功能。但是如果你必须这样做，这里有一些示例代码。注意:1) 我假设您使用的是 enctype="multipart/form-data"在你的 <form> . 2) 此代码旨在与仅包含您的 <input type="file" /> 的表单一起使用如果您想发布其他字段或多个文件，则必须更改代码。 3) 这意味着概念/示例的证明，它可能有错误，并且不是特别灵活。

static void Main(string[] args)
{
    HttpListener listener = new HttpListener();
    listener.Prefixes.Add("http://localhost:8080/ListenerTest/");
    listener.Start();

    HttpListenerContext context = listener.GetContext();

    SaveFile(context.Request.ContentEncoding, GetBoundary(context.Request.ContentType), context.Request.InputStream);

    context.Response.StatusCode = 200;
    context.Response.ContentType = "text/html";
    using (StreamWriter writer = new StreamWriter(context.Response.OutputStream, Encoding.UTF8))
        writer.WriteLine("File Uploaded");

    context.Response.Close();

    listener.Stop();

}

private static String GetBoundary(String ctype)
{
    return "--" + ctype.Split(';')[1].Split('=')[1];
}

private static void SaveFile(Encoding enc, String boundary, Stream input)
{
    Byte[] boundaryBytes = enc.GetBytes(boundary);
    Int32 boundaryLen = boundaryBytes.Length;

    using (FileStream output = new FileStream("data", FileMode.Create, FileAccess.Write))
    {
        Byte[] buffer = new Byte[1024];
        Int32 len = input.Read(buffer, 0, 1024);
        Int32 startPos = -1;

        // Find start boundary
        while (true)
        {
            if (len == 0)
            {
                throw new Exception("Start Boundaray Not Found");
            }

            startPos = IndexOf(buffer, len, boundaryBytes);
            if (startPos >= 0)
            {
                break;
            }
            else
            {
                Array.Copy(buffer, len - boundaryLen, buffer, 0, boundaryLen);
                len = input.Read(buffer, boundaryLen, 1024 - boundaryLen);
            }
        }

        // Skip four lines (Boundary, Content-Disposition, Content-Type, and a blank)
        for (Int32 i = 0; i < 4; i++)
        {
            while (true)
            {
                if (len == 0)
                {
                    throw new Exception("Preamble not Found.");
                }

                startPos = Array.IndexOf(buffer, enc.GetBytes("\n")[0], startPos);
                if (startPos >= 0)
                {
                    startPos++;
                    break;
                }
                else
                {
                    len = input.Read(buffer, 0, 1024);
                }
            }
        }

        Array.Copy(buffer, startPos, buffer, 0, len - startPos);
        len = len - startPos;

        while (true)
        {
            Int32 endPos = IndexOf(buffer, len, boundaryBytes);
            if (endPos >= 0)
            {
                if (endPos > 0) output.Write(buffer, 0, endPos-2);
                break;
            }
            else if (len <= boundaryLen)
            {
                throw new Exception("End Boundaray Not Found");
            }
            else
            {
                output.Write(buffer, 0, len - boundaryLen);
                Array.Copy(buffer, len - boundaryLen, buffer, 0, boundaryLen);
                len = input.Read(buffer, boundaryLen, 1024 - boundaryLen) + boundaryLen;
            }
        }
    }
}

private static Int32 IndexOf(Byte[] buffer, Int32 len, Byte[] boundaryBytes)
{
    for (Int32 i = 0; i <= len - boundaryBytes.Length; i++)
    {
        Boolean match = true;
        for (Int32 j = 0; j < boundaryBytes.Length && match; j++)
        {
            match = buffer[i + j] == boundaryBytes[j];
        }

        if (match)
        {
            return i;
        }
    }

    return -1;
}

为了帮助您更好地理解上面的代码在做什么，下面是 HTTP POST 的主体:

Content-Type: multipart/form-data; boundary=----WebKitFormBoundary9lcB0OZVXSqZLbmv

------WebKitFormBoundary9lcB0OZVXSqZLbmv
Content-Disposition: form-data; name="my_file"; filename="Test.txt"
Content-Type: text/plain

Test
------WebKitFormBoundary9lcB0OZVXSqZLbmv--

我省略了不相关的标题。如您所见，您需要通过扫描来解析正文以找到开始和结束边界序列，并删除文件内容之前的子标题。不幸的是，您不能使用 StreamReader，因为可能存在二进制数据。同样不幸的是，每个文件都没有 Content-Length(请求的 Content-Length header 指定了正文的总长度，包括边界、子 header 和间距。

关于c# - Httplistener 和文件上传，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/8466703/