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send image via tcp/ip

Posted on 2008-10-30
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Last Modified: 2013-11-26
i am trying to send a picturebox image to a client computer using tcp.but im really struggling. i have converted the image to bytes before sending it. but i am having trouble converting the bytes back to image once it gets to the client. how do i determine the about of bytes to be read.
Server Side code'''''''''''''''''''''''''''''''''''''''
 Public Sub start()
        Listener.Start()
        Client = Listener.AcceptTcpClient
        Stream = Client.GetStream()
        '----
        w = New BinaryWriter(Stream)
        r = New BinaryReader(Stream)
        '----
        If r.ReadString() = "RequestConnect" Then
            w.Write("Connected")
            Do
                w.Write(imageToByteArray(Form1.PictureBox1.Image))
                w.Write("Connected")
            Loop Until r.ReadString() = "Disconnect"
            w.Write("Disconnected")
        End If
        Client.Close()
        Listener.Stop()
    End Sub
 
    Public Function imageToByteArray(ByVal imageIn As Image) As Byte()
        Dim ms As MemoryStream = New MemoryStream()
        imageIn.Save(ms, System.Drawing.Imaging.ImageFormat.jpg)
        Return ms.ToArray()
    End Function
''---------------------------------------------------------------
 
CLIENT SIDE CODE''''''''''''''''''''''''''''''''''''''''''''''''''''
 Public Sub connect()
        Client.Connect(IP, port)
        Stream = Client.GetStream
        '----
        w = New BinaryWriter(Stream)
        r = New BinaryReader(Stream)
        '----
        
        w.Write("RequestConnect")
        If r.ReadString() = "Connected" Then
            Do
 ''HERES THE PROBLEM. how do i determine the amount of bytes to read
    Form1.PictureBox1.Image = byteArrayToImage(r.ReadBytes(126643))
                Application.DoEvents()
                w.Write("RequestConnect")
            Loop Until r.ReadString() = "Disconnected"
        End If
        Client.Close()
    End Sub
 
 Public Function byteArrayToImage(ByVal byteArrayIn() As Byte) As Image
        Dim ms As MemoryStream = New MemoryStream(byteArrayIn)
        Dim returnImage As Image = Image.FromStream(ms)
        Return returnImage
    End Function

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Question by:carl5121
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drichards earned 1000 total points
ID: 22846127
The best way to do it would be to send a header indicating the number of bytes to expect.  That way you can be sure to get them all.  Without that, the best you can do is to have a fixed size buffer (say 1024 bytes) and use the Read method.  You don't need the binary reader for this as it exists on the stream itself.

After doing a read, you transfer the bytes to a MemoryStream and then read again.  You read until no bytes are received for some period of time.  The problem is that you cannot predict the correct wait time as it might range from milliseconds to many seconds, or the data may not show up at all due to network conditions.  The most robust way to do it will be to send the image size in bytes ahead of the image data.  You'll need to make the header a fixed size so you know where the header ends and the image data starts.
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Author Closing Comment

by:carl5121
ID: 31511682
thank you for your help. i've been looking for an answer for a week. i joined this website today and a good choice that was.
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Expert Comment

by:agoud
ID: 25328194
This is how I do it with messages but it will have to be adapted to 'adding to the byte array'. I believe the keyphrase here is "While stream.DataAvailable". You will also have to use the stream (from Client.GetStream) directly. This is simply another way to do it.


While stream.DataAvailable
       i = stream.Read(bytes, 0, bytes.Length)
      Msg = Msg + System.Text.Encoding.ASCII.GetString(bytes, 0, i)
      Console.WriteLine("Received: {0}", Msg)
End While

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