.net - 带有 HttpWebRequest 的 HTTP POST

Question

我正在尝试发布一些数据，就好像我在 HTML 站点上使用 FORM (ContentType = multipart/form-data)。目标是亚马逊的s3。我正在使用 HttpWebRequest/HttpWebResponse，对我来说一切似乎都很好，但我仍然无法解决一个问题，我不断收到错误消息:

<?xml version="1.0" encoding="UTF-8"?>
<Error>
  <Code>InvalidArgument</Code>
  <Message>POST requires exactly one file upload per request.</Message>
  <ArgumentValue>0</ArgumentValue>
  <ArgumentName>file</ArgumentName>
</Error>

好像是自述的，不过我真的是把"file"字段发过去了。我已经成功地通过测试网站发送了一个没有问题的文件，整个后期数据似乎完全一样。当我通过 wireshark“监视”请求时，所有 header 和发布数据也都出现了 - 它如预期的那样存在。

有谁知道为什么亚马逊看不到"file"字段？

使用的代码(它被删减了一点以使其更具可读性):

private void addStringToStream(string buff, Stream s)
{
    var bytes = Encoding.UTF8.GetBytes(buff);
    s.Write(bytes, 0, bytes.Length);

    counter += bytes.Length;
}

private void doPost()
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);

    request.Method = "POST";
    request.ProtocolVersion = new Version(1, 1);

    request.KeepAlive = true;
    request.AllowAutoRedirect = true;

    request.Headers.Add("Accept-Language", "en-us,en;q=0.5");
    request.Headers.Add("Accept-Encoding", "gzip,deflate");
    request.Headers.Add("Accept-Charset", "ISO-8859-1,utf-8;q=0.7,*;q=0.7");

    request.Accept = "text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5";
    request.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.10) Gecko/20071115 Firefox/2.0.0.10";

    string boundary = "---------------------------317205771417341028";
    request.ContentType = "multipart/form-data; boundary=" + boundary;

    request.SendChunked = false;
    request.Credentials = CredentialCache.DefaultCredentials;
    request.CookieContainer = new CookieContainer();

    request.ContentLength = calculateLength();

    using (Stream s = request.GetRequestStream())
    {
        boundary += "\n";

        string inLineContentH = "Content-Disposition: form-data; name=\"{0}\"";
        string contentH = "Content-Disposition: form-data; name=\"{0}\"" + "\n" + "\n";

        string keyH = "key";

        string aclH = "acl";
        string aclV = "public-read";

        string accessKeyH = "AWSAccessKeyId";
        string accessKeyV = publicKey;

        string policyH = "policy";
        string policyV = this.generatePolicy();

        string signatureH = "signature";
        string signatureV = generateSignature(policyV);

        string fileH = "file";
        string fileContentNameH = "filename=\"{0}\"";
        string contentType2H = "Content-Type: application/octet-stream";

        buff = boundary;
        addStringToStream(buff, s);

        buff = string.Format(contentH, keyH);
        addStringToStream(buff, s);

        buff = keyV + "\n";
        addStringToStream(buff, s);

        /* here are all of the others necessary fields added to stream just as the one above
        no other operations are used, just adding bytes to stream 
        and finally we get to the file: */

        buff = boundary;
        addStringToStream(buff, s);

        buff = string.Format(inLineContentH, fileH) + "; " + string.Format(fileContentNameH, Path.GetFileName(this.FilePath)) + "\n";
        addStringToStream(buff, s);

        buff = contentType2H + "\n" + "\n";
        addStringToStream(buff, s);

        var inStream = File.OpenRead(FilePath);
        int val;
        while ((val = inStream.ReadByte()) != -1)
        {
            s.WriteByte((byte)val);
            counter++;
        }

        buff = "\n";
        addStringToStream(buff, s);

        buff = boundary;
        addStringToStream(buff, s);

        buff = string.Format(contentH, "submit");
        addStringToStream(buff, s);

        buff = "Upload to Amazon S3" + "\n";
        addStringToStream(buff, s);

        buff = boundary.Replace("\r", "").Replace("\n", "") + "--";
        addStringToStream(buff, s);
    }

    request.GetResponse();
}

发布到流的数据:

---------------------------317205771417341028
Content-Disposition: form-data; name="key"

webtest/image.png
---------------------------317205771417341028
Content-Disposition: form-data; name="acl"

public-read
---------------------------317205771417341028
Content-Disposition: form-data; name="AWSAccessKeyId"

AKIAJOQLTUC5H2NJ65NA
---------------------------317205771417341028
Content-Disposition: form-data; name="policy"

Oi8vd3d3Lmdvb2dsZS[...]c3QiXSwNCiAgXQ0KfQ0K
---------------------------317205771417341028
Content-Disposition: form-data; name="Signature"

06GBK5DJ71aB[...]M8Ct8JOE=
---------------------------317205771417341028
Content-Disposition: form-data; name="file"; filename="eclipse.png"
Content-Type: application/octet-stream

‰PNG

IHDRn
[...the rest of the image...]
IEND®B‚
---------------------------317205771417341028
Content-Disposition: form-data; name="submit"

Upload to Amazon S3
---------------------------317205771417341028--

还有...wireshark 的列表:

OUT TCP 58383 > http [SYN] Seq=0 Win=8192 Len=0 MSS=1460 WS=2 SACK_PERM=1
IN  TCP http > 58383 [SYN, ACK] Seq=0 Ack=1 Win=8190 Len=0 MSS=1460 WS=6 SACK_PERM=1
OUT TCP 58383 > http [ACK] Seq=1 Ack=1 Win=65700 Len=0
OUT TCP [TCP segment of a reassembled PDU]
IN  HTTP    HTTP/1.1 100 Continue 
OUT TCP [TCP segment of a reassembled PDU]
OUT TCP [TCP segment of a reassembled PDU]
OUT TCP [TCP segment of a reassembled PDU]
OUT TCP [TCP segment of a reassembled PDU]
IN  TCP http > 58383 [ACK] Seq=26 Ack=2031 Win=1331456 Len=0
OUT TCP [TCP segment of a reassembled PDU]
OUT TCP [TCP segment of a reassembled PDU]
IN  TCP http > 58383 [ACK] Seq=26 Ack=3969 Win=1337344 Len=0
OUT TCP [TCP segment of a reassembled PDU]
OUT TCP [TCP segment of a reassembled PDU]
IN  TCP http > 58383 [ACK] Seq=26 Ack=6889 Win=1343232 Len=0
OUT TCP [TCP segment of a reassembled PDU]
OUT TCP [TCP segment of a reassembled PDU]
IN  TCP http > 58383 [ACK] Seq=26 Ack=8441 Win=1346048 Len=0
OUT HTTP    POST / HTTP/1.1
//the one above contains the last bytes added to the stream
IN  TCP http > 58383 [ACK] Seq=26 Ack=10225 Win=1348864 Len=0
IN  TCP http > 58383 [ACK] Seq=26 Ack=10857 Win=1351936 Len=0
IN  TCP http > 58383 [ACK] Seq=26 Ack=12162 Win=1354752 Len=0
IN  TCP http > 58383 [ACK] Seq=26 Ack=13622 Win=1357824 Len=0
IN  TCP http > 58383 [ACK] Seq=26 Ack=13913 Win=1360640 Len=0
IN  TCP [TCP segment of a reassembled PDU]
IN  HTTP/XML    HTTP/1.1 400 Bad Request 
//the one above includes the error info quoted in the beginning
IN  TCP http > 58383 [FIN, ACK] Seq=649 Ack=13913 Win=1360640 Len=0
OUT TCP 58383 > http [ACK] Seq=13913 Ack=650 Win=65052 Len=0
OUT TCP 58383 > http [FIN, ACK] Seq=13913 Ack=650 Win=65052 Len=0
IN  TCP http > 58383 [ACK] Seq=650 Ack=13914 Win=1360640 Len=0

上述报告与基于网络应用程序的上传生成的报告之间的唯一区别在于，基于网络应用程序的[重组 PDU 的 TCP 段] 位置较少，并且有一些 [TCP Dup ACK 156#1] http > 58364 [ACK] Sq=1 Ack=7017 Win=11668 Len=0 条目(如果可能有帮助，我可以发送完整的跟踪)。

Answer 1

解决了!边界是错误的 - 需要为发布数据添加比 header 中的值多 2 个破折号。上面的代码需要做的是:

string boundary = "---------------------------317205771417341028";
request.ContentType = "multipart/form-data; boundary=" + boundary;

[...]

using (Stream s = request.GetRequestStream())
{
    boundary = "--" + boundary "\n";

[...]如此简单……但又如此烦人……