Question

我正在尝试使用httpwebrequests构建一个从自定义网络服务器下载小二进制文件（20-25 KB）的应用程序。

这是服务器端代码：

Stream UpdateRequest = context.Request.InputStream;
byte[] UpdateContent = new byte[context.Request.ContentLength64];
UpdateRequest.Read(UpdateContent, 0, UpdateContent.Length);
String remoteVersion = "";
for (int i = 0;i < UpdateContent.Length;i++) { //check if update is necessary
    remoteVersion += (char)UpdateContent[i];
}

byte[] UpdateRequestResponse;

if (remoteVersion == remotePluginVersion) {
    UpdateRequestResponse = new byte[1];
    UpdateRequestResponse[0] = 0; //respond with a single byte set to 0 if no update is required
} else {
    FileInfo info = new FileInfo(Path.Combine(Directory.GetCurrentDirectory(), "remote logs", "PointAwarder.dll"));
    UpdateRequestResponse = File.ReadAllBytes(Path.Combine(Directory.GetCurrentDirectory(), "remote logs", "PointAwarder.dll"));
    //respond with the updated file otherwise
}

//this byte is past the threshold and will not be the same in the version the client recieves
Console.WriteLine("5000th byte: " + UpdateRequestResponse[5000]);

//send the response
context.Response.ContentLength64 = UpdateRequestResponse.Length;
context.Response.OutputStream.Write(UpdateRequestResponse, 0, UpdateRequestResponse.Length);
context.Response.Close();

在此之后，数组UpdateRequestResponse包含整个文件并已发送到客户端。

客户端运行此代码：

//create the request
WebRequest request = WebRequest.Create(url + "pluginUpdate");
request.Method = "POST";
//create a byte array of the current version
byte[] requestContentTemp = version.ToByteArray();
int count = 0;
for (int i = 0; i < requestContentTemp.Length; i++) {
    if (requestContentTemp[i] != 0) {
        count++;
    }
}
byte[] requestContent = new byte[count];
for (int i = 0, j = 0; i < requestContentTemp.Length; i++) {
    if (requestContentTemp[i] != 0) {
        requestContent[j] = requestContentTemp[i];
        j++;
    }
}

//send the current version
request.ContentLength = requestContent.Length;
Stream dataStream = request.GetRequestStream();
dataStream.Write(requestContent, 0, requestContent.Length);
dataStream.Close();

//get and read the response
WebResponse response = request.GetResponse();
Stream responseStream = response.GetResponseStream();
byte[] responseBytes = new byte[response.ContentLength];
responseStream.Read(responseBytes, 0, (int)response.ContentLength);
responseStream.Close();
response.Close();

//if the response containd a single 0 we are up-to-date, otherwise write the content of the response to file
if (responseBytes[0] != 0 || response.ContentLength > 1) {
    BinaryWriter writer = new BinaryWriter(File.Open(Path.Combine(Directory.GetCurrentDirectory(), "ServerPlugins", "PointAwarder.dll"), FileMode.Create));
    writer.BaseStream.Write(responseBytes, 0, responseBytes.Length);
    writer.Close();
    TShockAPI.Commands.HandleCommand(TSPlayer.Server, "/reload");
}

客户端上的字节数组responseBytes应该与服务器上的数组UpdateRequestResponse相同，但事实并非如此。在大约4000字节后，每个字节后设置为0而不是它应该是什么（responseBytes [3985]是最后一个非零字节）。

这是否因为httpWebRequest有大小限制而发生？我看不到我的代码中可能导致它的任何错误，并且相同的代码在我只需要传递短数据序列（少于100个字节）的其他实例中工作。

MSDN页面没有提及任何大小限制。

Answer 1

并不是说它有任何人为限制，这是你尝试做的Streaming性质的副产品。我觉得以下一行是罪犯：

responseStream.Read(responseBytes, 0, (int)response.ContentLength);

我过去曾遇到过这个问题（使用TCP流），但它并没有读取数组的所有内容，因为它们还没有通过网络发送过。我会尝试这样做。

for (int i = 0; i < response.ContentLength; i++)
{
   responseBytes[i] = responseStream.ReadByte();
}

这样，它将确保一直读到流的结尾。

修改

基于BinaryReader的{{1}}解决方案效率更高。以下是相关解决方案：

BinaryReader binReader = new BinaryReader(responseStream); const int bufferSize = 4096; byte[] responseBytes; using (MemoryStream ms = new MemoryStream()) { byte[] buffer = new byte[bufferSize]; int count; while ((count = binReader.Read(buffer, 0, buffer.Length)) != 0) ms.Write(buffer, 0, count); responseBytes = ms.ToArray(); }

Answer 2

您假设Read正在读取您请求的字节数。但请求的数量只是一个上限。你必须容忍阅读小块。

您可以使用var bytes = new BinaryReader(myStream).ReadBytes(count);来读取确切的数字。不要经常调用ReadByte，因为这会占用大量CPU资源。

最好的解决方案是退出相当手动的HttpWebRequest并使用HttpClient或WebClient。所有这些都是自动化的，您可以获得byte[]。

C＃ - httpWebRequest流的大小是否有限制？

2 个答案: