c# - 使用 HttpWebRequest 时如何限制带宽使用？

Question

使用 HttpWebRequest 时如何限制带宽使用？

Answer 1

如果您在代码中执行此操作，我建议使用 Rx 之类的东西来帮助简化计时器的使用等。

class Uploader
{
    /// <summary>Thread-safe flag to ensure that a packet isn't currently sending</summary>
    private volatile bool isPacketSending = false;

    /// <summary>
    /// HTTP Posts a stream to a web address with a maximum bytes per second until the file is uploaded
    /// </summary>
    /// <param name="address">The web address to post the file to</param>
    /// <param name="requestBody">The request body to stream at a maximum speed</param>
    /// <param name="bytesPerSecond">The maximum number of bytes to send every second</param>
    /// <returns>Returns an observable sequence of the bytes read so far</returns>
    public IObservable<long> PostStreamThrottledAsync(Uri address, Stream requestBody, int bytesPerSecond)
    {
        if (!requestBody.CanRead)
        {
            throw new InvalidOperationException("Request body stream cannot be read from");
        }

        return Observable.Using(
            () =>
                {
                    var client = new WebClient();
                    return client.OpenWrite(address);
                },
            outputStream => Observable.Return(0L).Concat(Observable.Interval(TimeSpan.FromSeconds(1)))
                        .TakeWhile(tick => SendPacket(requestBody, outputStream, bytesPerSecond) != 0)
                        .Select(_ => requestBody.Position));
    }


    /// <summary>
    /// Sends a packet up to the maximum bytes specified
    /// </summary>
    /// <param name="requestBody">The stream to read from</param>
    /// <param name="output">The stream to write to</param>
    /// <param name="bytesPerSecond">The number of bytes to send</param>
    /// <returns>Returns the number of bytes actually sent; zero if at end of stream; -1 if we are exceeding throughput capacity.</returns>
    private int SendPacket(Stream requestBody, Stream output, int bytesPerSecond)
    {
        if (isPacketSending)
        {
            return -1;
        }

        try
        {
            isPacketSending = true;
            var buffer = new byte[bytesPerSecond];
            var bytesRead = requestBody.Read(buffer, 0, bytesPerSecond);
            if (bytesRead != 0)
            {
                output.Write(buffer, 0, bytesRead);
            }

            return bytesRead;
        }
        finally
        {
            isPacketSending = false;
        }
    }
}

Answer 2

您可以将Proxy 属性连接到带宽限制的 HTTP 代理，例如Squid 可以做到这一点。也许不是一个方便的解决方案，但它肯定会奏效。