C# - 通过 WebRequest 和 HttpListener 发送/接收和保存 XML 文件

Question

我正在制作一个 ASP.NET Web 应用程序，我用它来编辑 Windows 服务的设置（一个 XML 文件）。 Windows 服务可以与 Web 应用程序在同一台服务器上运行，我已经让它完美运行，我遇到的问题是当 Windows 服务在不同的服务器上运行并且 Web 应用程序需要将 Xml 文件发送到Windows 服务。

我的目标是让 ASP.NET Web 应用程序将刚刚通过 Http 更新的 XML 文件发送到具有 HttpListener 的 Windows 服务。

到目前为止我所管理的：

ASP.NET 应用程序：

public string PushSettings(string serverName, string xmlFile)
{
    var prefix = "http://" + serverName+ ":";
    var portnumber = ConfigurationManager.AppSettings["PortNumber"];
    var command = ConfigurationManager.AppSettings["PushSettingsCommand"];
    var request = (HttpWebRequest)WebRequest.Create(prefix + portnumber + command);
    var bytes = System.Text.Encoding.ASCII.GetBytes(xmlFile);
    request.ContentType = "text/xml; encoding='utf-8'";
    request.ContentLength = bytes.Length;
    request.Method = "POST";
    var requestStream = request.GetRequestStream();
    requestStream.Write(bytes, 0, bytes.Length);
    requestStream.Close();

    try
    {
        var response = (HttpWebResponse)request.GetResponse();
        return response.StatusCode.ToString();
    }
    catch (WebException ex)
    {
        Log.Info("WebException thrown while trying to connect to httplistener. Exception message: " + ex.Message + " The following request was attempted: " + prefix + portnumber + command);
        throw new WebException("WebException thrown while trying to connect to httplistener. Exception message: " + ex.Message + " The following request was attempted: " + prefix + portnumber + command);
    }
}

(string xmlFile是整个XML文件的字符串)

Windows 服务：

public void RunHttpListener()
{
    var listener = new HttpListener();
    try
    {
        listener.Prefixes.Add(_Prefix);

        listener.Start();

        var context = listener.GetContext();
        var request = context.Request;
        var ipAdress = context.Request.RemoteEndPoint?.ToString();

        if(_Prefix.Contains("PushSettings"))
        {
            SaveFile(context.Request.ContentEncoding, getSettings.GetBoundary(context.Request.ContentType), context.Request.InputStream);
        }

        var response = context.Response;
        const HttpStatusCode responseString = HttpStatusCode.OK;
        var buffer = Encoding.UTF8.GetBytes(responseString.ToString());
        response.ContentLength64 = buffer.Length;
        var output = response.OutputStream;
        output.Write(buffer, 0, buffer.Length);
        output.Close();
        listener.Stop();
    }
    catch (Exception ex)
    {
        Log.Info(ex.Message);
        if (listener.IsListening)
        {
            listener.Stop();
        }
    }
}

(_Prefix 例如：{serverName}/PushSettings)

GetBoundary() 和 SaveFile() 是我在 Stack Overflow 线程上找到的代码：Httplistener and file upload，它会引发异常，因为 len == 0 在第三次循环通过第一个 while （真的） { }。这是该线程的代码：

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

public void SaveFile(Encoding enc, String boundary, Stream input)
{
    var boundaryBytes = enc.GetBytes(boundary);
    var boundaryLen = boundaryBytes.Length;

    using (var output = new FileStream("Settings.xml", FileMode.Create, FileAccess.Write))
    {
        var buffer = new Byte[1024];
        var len = input.Read(buffer, 0, 1024);
        var 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 (var 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)
        {
            var 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;
            }
        }
    }
}

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

        if (match)
        {
            return i;
        }
    }

    return -1;
}

这是 XML 文件外观的（缩短的）示例

<?xml version="1.0" encoding="UTF-8"?>
<MonitorSettings>
  <Interval>30000</Interval>
  <QueuCheck>False</QueuCheck>
  <MailAlert>False</MailAlert>
  <WindowsServices>mongodb</WindowsServices>
</MonitorSettings>

到目前为止，我的 Windows 服务代码能够接收来自 Web 应用程序的请求，但是由于 len == 0 时引发的异常，它没有保存 XML 文件。我做错了什么吗？有没有更好的方法来做事？有什么好的 StackOverflow 线程可以提供帮助吗？

编辑 更准确地说，异常是在函数 SaveFile() 中引发的，第三次在 while(true){ } 中循环：

if (len == 0)
{
    throw new Exception("Start Boundaray Not Found");
}

Answer 1

看起来我使用了一种过于复杂的方法来尝试将请求的正文保存到 XML 文件中。我做了一些研究，发现这段代码可以工作：

    public void SaveFile(HttpListenerContext context)
    {
        // Get the data from the HTTP stream
        var body = new StreamReader(context.Request.InputStream).ReadToEnd();

        var xmlDocument = new XmlDocument();
        xmlDocument.LoadXml(body);
        xmlDocument.Save("Settings.xml");
    }