的HttpListener和文件上传 [英] Httplistener and file upload
问题描述
我尝试从我的web服务器上传的文件。当客户端通过一个WebForm（随机文件）将它的文件，我需要解析获取文件出来，并进一步在处理它的请求。
基本上，代码都为：
I am trying to retrieve an uploaded file from my webserver. As the client sends its files through a webform (random files), I need to parse the request to get the file out and to process it further on. Basically, the code goes as:
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
其结果是，我能够检索TEXTFILES，但对于所有其他文件，这些文件已损坏。
有人能告诉我如何分析这些HttplistnerRequests正确（或提供轻量化的替代）？
As a result, i am able to retrieve textfiles, but for all other files, they are corrupted. Could someone tell me how to parse these HttplistnerRequests properly (or providing a lightweighted alternative)?
推荐答案
我想你通过与的HttpListener ，而这样做不是使用内置在ASP.Net的设施，使事情对自己的难度比必要的。但是，如果你必须做在这里这样一些示例代码。注：1）我假设你正在使用 ENCTYPE =的multipart / form-data的在<形式> 。 2）该代码被设计成与包含表单只能使用你的<输入类型=文件/> 如果你要发布其他领域或多个文件时将不得不更改代码。 3）这意味着是概念/示例的证明，它可能有错误，并且没有特别灵活
I think you are making things harder on yourself than necessary by doing this with an HttpListener rather than using the built in facilities of ASP.Net. But if you must do it this way here is some sample code. Note: 1) I'm assuming you're using enctype="multipart/form-data" on your <form>. 2) This code is designed to be used with a form containing only your <input type="file" /> if you want to post other fields or multiple files you'll have to change the code. 3) This is meant to be a proof of concept/example, it may have bugs, and is not particularly flexible.
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是干什么的，这里是什么在HTTP POST的身体看起来像：
To help you better understand what the code above is doing, here is what the body of the HTTP POST looks like:
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary9lcB0OZVXSqZLbmv
------WebKitFormBoundary9lcB0OZVXSqZLbmv
Content-Disposition: form-data; name="my_file"; filename="Test.txt"
Content-Type: text/plain
Test
------WebKitFormBoundary9lcB0OZVXSqZLbmv--
我已经离开了不相干的头。正如你所看到的，你需要通过扫描来查找开始和结束边界序列解析身体，并删除子头文件的内容之前出现。不幸的是你不能使用的StreamReader因为二进制数据的潜力。也不幸的是，没有每个文件内容长度（内容长度报头的请求指定了主体包括边界，子标头，和间隔的总长度。
I've left out the irrelevant headers. As you can see, you need to parse the body by scanning through to find the beginning and ending boundary sequences, and drop the sub headers that come before the content of your file. Unfortunately you cannot use StreamReader because of the potential for binary data. Also unfortunate is the fact that there is no per file Content-Length (the Content-Length header for the request specifies the total length of the body including boundaries, sub-headers, and spacing.
这篇关于的HttpListener和文件上传的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
