Picture box is not displaying image coming from the TCP socket - winforms

Question

I am developing a TCP client - server program that the client will capture its screenshot and send it to the server via TCP socket continuously. The server will display the image in a picture box. As of now the image transfer between client and server is working fine but the image is not displaying in the picture box.
Server side code:
private void startListening()
{
//label1.Text = "Server is starting...";
Console.WriteLine("Server is starting...");
byte[] data = new byte[1024];
IPEndPoint ipep = new IPEndPoint(IPAddress.Any, 9050);
Socket newsock = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
newsock.Bind(ipep);
newsock.Listen(10);
//label1.Text="Waiting for a client...";
Socket client = newsock.Accept();
IPEndPoint newclient = (IPEndPoint)client.RemoteEndPoint;
//label1.Text = "Connected to client.";
while (true)
{
data = ReceiveVarData(client);
MemoryStream ms = new MemoryStream(data);
try
{
lock (this)
{
Image img = Image.FromStream(ms);
pictureBox1.Image = img;
pictureBox1.Invoke((MethodInvoker)delegate
{
pictureBox1.Refresh();
});
}
}
catch (ArgumentException e)
{
Console.WriteLine("something broke");
}
if (data.Length == 0)
newsock.Listen(10);
}
//Console.WriteLine("Disconnected from {0}", newclient.Address);
client.Close();
newsock.Close();
/////////////////////////////////////////////
}
private byte[] ReceiveVarData(Socket client)
{
int total = 0;
int recv;
byte[] datasize = new byte[4];
recv = client.Receive(datasize, 0, 4, 0);
int size = BitConverter.ToInt32(datasize, 0);
int dataleft = size;
byte[] data = new byte[size];
while (total < size)
{
recv = client.Receive(data, total, dataleft, 0);
if (recv == 0)
{
break;
}
total += recv;
dataleft -= recv;
}
return data;
}
private void button1_Click(object sender, EventArgs e)
{
var t = new Thread(startListening);
t.IsBackground = true;
t.Start();
}
Client side code:
static void Main(string[] args)
{
byte[] data = new byte[1024];
int sent;
IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 9050);
Socket server = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
try
{
server.Connect(ipep);
}
catch (SocketException e)
{
Console.WriteLine("Unable to connect to server.");
Console.WriteLine(e.ToString());
Console.ReadLine();
}
while (true)
{
Bitmap bmp = captureImage();
MemoryStream ms = new MemoryStream();
// Save to memory using the Jpeg format
bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
// read to end
byte[] bmpBytes = ms.ToArray();
bmp.Dispose();
ms.Close();
sent = SendVarData(server, bmpBytes);
//Console.WriteLine("Disconnecting from server...");
}
}
private static Bitmap captureImage()
{
Bitmap bmpScreenshot = null;
try
{
//Create a new bitmap.
bmpScreenshot = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
Screen.PrimaryScreen.Bounds.Height,
PixelFormat.Format32bppArgb);
}
catch (Exception ex)
{
Console.WriteLine("Image covertion exception: " + ex);
}
return bmpScreenshot;
}
private static int SendVarData(Socket s, byte[] data)
{
int total = 0;
int size = data.Length;
int dataleft = size;
int sent;
byte[] datasize = new byte[4];
datasize = BitConverter.GetBytes(size);
sent = s.Send(datasize);
while (total < size)
{
sent = s.Send(data, total, dataleft, SocketFlags.None);
total += sent;
dataleft -= sent;
}
return total;
}
}

Answer 1

I think your issue may be that you try to manipulate the GUI component from the network thread which this code:
lock (this)
{
Image img = Image.FromStream(ms);
pictureBox1.Image = img; // Access from network thread to GUI component
pictureBox1.Invoke((MethodInvoker)delegate
{
pictureBox1.Refresh();
});
}
You should do the following:
// No lock here - it's not needed
// The image data is created on the network thread, it get's captured
// by the closure and will only get applied on the UI thread
// If this also doesn't work you might try to capturing the MemoryStream
// and transfer that to the GUI thread
Image img = Image.FromStream(ms);
pictureBox1.Invoke((MethodInvoker)delegate
{
pictureBox1.Image = img;
pictureBox1.Refresh();
});
Some minor issues that I also found:
You don't handle endOfStream (recv == 0) completely. In that case you would try to pass an uncompletely received image to the GUI instead of stopping reception.
You are not capturing exceptions from the stream and cleanup in case it happens. This means your receive thread could crash. Consider using try/catch/finally. And/or a using which manages the lifetime of your socket.
You are not checking whether all bytes were received and have been sent on sending/receiving the 4 header bytes.