ASP.NET - remote screenshot - asp.net

Question

I made a very very simple small app to take screenshot of the desktop and send to network share. About 10 PC's would have this app installed.
My idea is, that there will be one dashboard in ASP.NET, which simply shows those screenshots on the webpage. So far, easy stuff.
But, because I don't want to clog the network and send the screenshot every 1 minute, I would like to launch the .exe on the remote PC's by demand of ASP.NET user.
Unfortunately I haven't found any information (and I'm a complete ASP.NET n00b), how to launch remote executable IN the context of the remote PC (so I won't see screenshots of ASP server :) )
If there is no such possibility, please advise about other way to solve this.

Answer 1

Update after clarification:
Take a look at the situation from another angle:
Why don't you run a web server on the clients that host an asp.net page that triggers the capture. Then you can, from your root server, simply sent http requests to the clients and fetch the image.
You can try http://CassiniDev.codeplex.com - it supports external IP and hostnames.
And you may also consider simply embedding the CassiniDev-lib (a very simple example is shown here - Using CassiniDev to host ASP.Net in your application, that way you can use the web server as the reciever and the forms app can do whatever it wants on the client.
I am confident in this approach as I designed cassinidev with this as one of the primary use cases.
From asp.net you cannot. It is only HTML/JavaScript once it gets to the browser.
ActiveX is a possibility but it is quite painful and dated and limited. And painful.
The new way to do something like this is to deploy a .net Forms application or WPF app via Click Once.
You can also write a WPF Browser Application but getting the kind of permissions you would need would entail setting the site as full trust.

Answer 2

If a web page could launch an arbitrary .exe file on your machine, that would be a security disaster.
However, since these are your PCs, you can require them to install an ActiveX control of some kind that you could then embed in your ASP.NET page.

Answer 3

As others have said, there is really no way for ASP.Net to call out to the apps, but reversing the control flow should work OK...
I suppose you could have the grabber application running all the time on the users desktop, but have it make a call to a web service / file served by the server that contains an instruction for that instance of the app to grab a screenshot.
Something like...
App : Do I have to do anything? (GET /workinstruction.aspx)
Server : no. (server decides whether to request work, and return the result in (workinstruction.aspx)
App : (waits 1 minute)
App : Do I have to do anything?
Server : yes.
App : (takes screenshot and submits)
App : (waits 1 minute)
App : Do I have to do anything?
etc...

Answer 4

Thank you all for answering, those were interesting approaches to the subject.
Yet due to many factors I ended up with following solution:
Pseudo-service (Windows Forms with tray icon and hidden form) application on client PC's. It is serving as TCP server.
ASP.Net web app on the server, with TCP client function.
On request of the web user, web app is sending preformatted TCP 'activation' string to the chosen PC. Tray app is making a screenshot and sending it to predefined SMB share, available for web app to display.
Thanks again!

Answer 5

I've done this exact thing a few times for monitoring remote display systems. What I found was that using MiniCap.exe to capture image also took video (which was required on remote display systems).
I also used Cassini as described by Sky Sanders with an ASPX-page with the following code.
Then I just reference the page from an img src="http://computer/page.aspx?paramters". (Let me know if you need more info)
<%# Import NameSpace="System.IO" %>
<%# Import NameSpace="System.Drawing" %>
<%# Import NameSpace="System.Drawing.Imaging" %>
<%# Import NameSpace="System.Diagnostics" %>
<%
Response.Buffer = True
Response.BufferOutput = True
Dim CompressionLevel As Integer = 1
Dim compress As Integer = 1
If Not Request.Item("compress") Is Nothing Then
If IsNumeric(Request.Item("compress")) = True Then
CompressionLevel = CInt(Request.Item("compress"))
End If
End If
compress = CompressionLevel
' Resize requested?
Dim SizeX As Integer = 100
Dim SizeY As Integer = 75
If Not Request.Item("width") Is Nothing Then
If IsNumeric(Request.Item("width")) = True Then
SizeX = CInt(Request.Item("width"))
CompressionLevel = 10
End If
End If
If Not Request.Item("height") Is Nothing Then
If IsNumeric(Request.Item("height")) = True Then
SizeY = CInt(Request.Item("height"))
CompressionLevel = 10
End If
End If
Dim Region As String = ""
If Not Request.Item("region") Is Nothing Then
Region = Request.Item("region")
End If
Dim XS As Integer = 0
Dim YS As Integer = 0
Dim XE As Integer = 1023
Dim YE As Integer = 766
Try
If Region.IndexOf(",") > -1 Then
Dim Rec() As String = Region.Split(",")
If Rec.GetUpperBound(0) >= 3 Then
If IsNumeric(Rec(0)) Then XS = Rec(0)
If IsNumeric(Rec(1)) Then YS = Rec(1)
If IsNumeric(Rec(2)) Then XE = Rec(2)
If IsNumeric(Rec(3)) Then YE = Rec(3)
End If
End If
Catch : End Try
Dim FileType As String = "jpg"
Dim MimeType As String = "jpeg"
If Not Request.Item("filetype") Is Nothing Then
FileType = Request.Item("filetype")
MimeType = FileType
End If
If Not Request.Item("mimetype") Is Nothing Then
FileType = Request.Item("mimetype")
End If
Dim ImageFile As String = ""
Dim ImageThumbFile As String = ""
Dim ImageFolder As String = Server.MapPath("~/ScreenShots/")
If IO.Directory.Exists(ImageFolder) = False Then
IO.Directory.CreateDirectory(ImageFolder)
End If
' Delete files older than 30 minutes
For Each File As String In IO.Directory.GetFiles(ImageFolder)
Response.Write("File: " & File & "<br>")
If IO.File.GetCreationTimeUtc(File).AddMinutes(30) < Now.ToUniversalTime Then
IO.File.Delete(File)
End If
Next
' Find available filename
Dim tmpC As Integer = 0
While tmpC < 100
tmpC += 1
ImageFile = "ScreenShot_" & CStr(tmpC).PadLeft(5, "0") & "." & FileType
ImageThumbFile = "ScreenShot_" & CStr(tmpC).PadLeft(5, "0") & "_thumb." & FileType
If IO.File.Exists(ImageFolder & "\" & ImageFile) = False Then
' Found our filename
' Reserve it
Dim ios As IO.FileStream = IO.File.Create(ImageFolder & "\" & ImageFile)
ios.Close()
ios = Nothing
Exit While
End If
End While
' Run MiniCap
' " -capturedesktop" & _
Dim CMD As String = """" & Server.MapPath("/MiniCap.EXE") & """" & _
" -save """ & ImageFolder & "\" & ImageFile & """" & _
" -captureregion " & XS & " " & YS & " " & XE & " " & YE & _
" -exit" & _
" -compress " & CompressionLevel
If Not CMD Is Nothing Then
Dim myProcess As Process = New Process
Dim RouteFB As String
With myProcess
With .StartInfo
.FileName = "cmd.exe"
.UseShellExecute = False
.CreateNoWindow = True
.RedirectStandardInput = True
.RedirectStandardOutput = True
.RedirectStandardError = True
End With
.Start()
End With
Dim sIn As IO.StreamWriter = myProcess.StandardInput
sIn.AutoFlush = True
' Create stream reader/writer references
Dim sOut As IO.StreamReader = myProcess.StandardOutput
Dim sErr As IO.StreamReader = myProcess.StandardError
' Send commands
sIn.Write(CMD & System.Environment.NewLine)
sIn.Write("exit" & System.Environment.NewLine)
' Wait one second
'Threading.Thread.CurrentThread.Sleep(60000)
' Read all data
Response.Write(sOut.ReadToEnd)
' Kill process if still running
If Not myProcess.HasExited Then
myProcess.Kill()
End If
sIn.Close()
sOut.Close()
sErr.Close()
myProcess.Close()
End If
Response.Clear()
Response.ClearContent()
If Not Request.Item("width") Is Nothing Or Not Request.Item("length") Is Nothing Then
' Resize, making thumbnail in desired size
Dim b As Bitmap = Bitmap.FromFile(ImageFolder & "\" & ImageFile)
Dim thumb As Bitmap = b.GetThumbnailImage(SizeX, SizeY, Nothing, IntPtr.Zero)
' Jpeg image codec
Dim jpegCodec As ImageCodecInfo
' Get image codecs for all image formats
Dim codecs As ImageCodecInfo() = ImageCodecInfo.GetImageEncoders()
' Find the correct image codec
For i As Integer = 0 To codecs.Length - 1
If (codecs(i).MimeType = "image/" & MimeType) Then
jpegCodec = codecs(i)
Exit For
End If
Next i
Dim qualityParam As New EncoderParameter(System.Drawing.Imaging.Encoder.Quality, compress * 10)
Dim encoderParams As New EncoderParameters(1)
encoderParams.Param(0) = qualityParam
thumb.Save(ImageFolder & "\" & ImageThumbFile, jpegCodec, encoderParams)
thumb.Dispose()
b.Dispose()
' Send thumb
Response.TransmitFile(ImageFolder & "\" & ImageThumbFile)
Else
' Send normal file
Response.TransmitFile(ImageFolder & "\" & ImageFile)
End If
Response.End()
%>