为什么我的网络流下载 0 字节？

Question

我目前正在从事一个项目，该项目涉及我使用笔记本电脑的相机在给定命令下拍照。我现在将我的网络摄像头用作安全摄像头，因为我还没有时间购买真正的摄像头，所以我的笔记本电脑必须这样做。 项目结构如下：

我有我的服务器（在我的笔记本电脑上运行）和我的客户端（在我的 PC 上运行，稍后将在我的手机上运行 - 但那不相关）。我使用我的客户端（在本例中为“网络摄像头”）向服务器发送一个命令，服务器接收它，使用网络摄像头拍照，获取字节，然后通过网络流将字节发送给客户端。

但是，当我使用客户端下载流时，它会下载 0 个字节。澄清一下，它确实将图像保存在我的文件夹中，但我无法打开它，因为它是 0 字节。

服务器

        while (true)
        {
            if (nwStream.DataAvailable)
            {
                //Create a byte array (a buffer). This will hold the byte size that we recieve from the client in memory.
                byte[] buffer = new byte[client.ReceiveBufferSize];

                //Now we need to read the bytes and store the bytes we read in a int, we do this by using our nwStream.Read function and pass it the correct parameters.
                //1. [Buffer] - an array of type byte, and we declared that above [buffer] <- This is what we are reading from.
                //2. [Offset] - Now we need to set the offset, where we want to start reading in the buffer. so since its an array we start at 0.
                //3. [Size] - The number of bytes we want to read from the NetworkStream.
                int bytesRead = nwStream.Read(buffer, 0, client.ReceiveBufferSize);

                //Now we need to decode the message we recieved by using the Encoding.ASCII.GetString to get the string and passing the correct parameters.
                //1. [Bytes] - What we want to decode, this is where we give it a byte array 
                //2. [Index] - We need to give it the first index of the array that we want to decode so it knows where to start, we do this bya dding 0 since its an array.
                //3. [Count] - The number of bytes we want to decode and we created an int to hold that number above so let's pass it as a parameter.
                string dataRecieved = Encoding.Default.GetString(buffer, 0, bytesRead);
                if (dataRecieved == "webcam")
                {
                    Console.WriteLine("Starting the webcam feature..");
                    CameraFeature();

                }
            }
        }

    }

    private static void CameraFeature()
    {
        VideoCaptureDevices = new FilterInfoCollection(FilterCategory.VideoInputDevice);

        foreach (FilterInfo Device in VideoCaptureDevices)
        {
            Devices.Add(Device.Name);
            Console.WriteLine("Device: " + Device.Name);
        }

        FinalVideo = new VideoCaptureDevice(VideoCaptureDevices[0].MonikerString);

        FinalVideo.NewFrame += new NewFrameEventHandler(FinalVideo_NewFrame);
        FinalVideo.Start();
    }

    private static void exitcamera()
    {
        FinalVideo.SignalToStop();
        // FinalVideo.WaitForStop();  << marking out that one solved it
        FinalVideo.NewFrame -= new NewFrameEventHandler(FinalVideo_NewFrame); // as sugested
        FinalVideo = null;
    }

    static void FinalVideo_NewFrame(object sender, NewFrameEventArgs eventArgs)
    {

        Bitmap video = (Bitmap)eventArgs.Frame.Clone();
        //video.Save($"image{imgCount}.png");
        Console.WriteLine("Picture taken!");
        Connection(video);
        exitcamera();
        imgCount++;
    }


    public static void Connection(Bitmap tImage)
    {
        Console.WriteLine("Starting the transfer..");
        byte[] bStream = ImageToByte(tImage);

        try
        {
            nwStream.Write(bStream, 0, bStream.Length);
            Console.WriteLine("Done..");

        }
        catch (SocketException e1)
        {
            Console.WriteLine("SocketException: " + e1);
        }


    }

    static byte[] ImageToByte(Bitmap iImage)
    {
        MemoryStream mMemoryStream = new MemoryStream();
        iImage.Save(mMemoryStream, System.Drawing.Imaging.ImageFormat.Png);
        return mMemoryStream.ToArray();
    }
}

客户

private static void SendCommand()  
{
    while (true)
    {
        Console.WriteLine("Please enter a command: ");
        string userInput = Console.ReadLine();
        //Convert out string message to a byteArray because we will send it as a buffer later.
        byte[] bytesToSend = Encoding.Default.GetBytes(userInput);

        //Write out to the console what we are sending.
        Console.WriteLine("Sending: " + userInput);

        //Use the networkstream to send the byteArray we just declared above, start at the offset of zero, and the size of the packet we are sending is the size of the messages length.
        nwStream.Write(bytesToSend, 0, bytesToSend.Length);


        //RecieveBuffer();
        //Recieve the bytes that are coming from the other end (server) through the client and store them in an array.
        byte[] bytesToRead = new byte[client.ReceiveBufferSize];
        //byte[] bitmap = GetYourImage();


        //read the bytes, starting from the offset 0, and the size is what ever the client has recieved.
        int bytesRead = nwStream.Read(bytesToRead, 0, client.ReceiveBufferSize);

        //Decode the bytes we just recieved using the Encoding.ASCII.GetString function and give it the correct parameters
        //1. What it should decode
        //2. Starting to decode from what offset
        //3. How much do we want to decode?

        Bitmap bmp;
        using (var ms = new MemoryStream(bytesToRead))
        {
            bmp = new Bitmap(ms);
            bmp.Save("Image.png");
        }
        //Console.WriteLine("Recieved: " + Encoding.ASCII.GetString(bytesToRead, 0, bytesRead));


    }

Answer 1

在向客户端发送流之前尝试MemoryStream.Seek(0, SeekOrigin.Begin)。您可能会下载 0 个字节，因为当您收到它时会在其末尾流式传输。