Accessing Web Interface using VB .net

dan.husted — Wed, 20 Jun 2018 19:20:03 GMT

I am attempting to automate VRED through the Web Interface as described in this Autodesk University tutorial:

http://au.autodesk.com/au-online/classes-on-demand/class-catalog/2015/vred/at10281#chapter=0

The tutorial uses the following python script to attach to the web interface:

import urllib
import socket

# Function to send a command to VRED and optionally return a response.
def sendVredCmd(cmd, replyNeeded):
reply = None
cmd = urllib.quote(cmd)
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("localhost", 8888))
s.send("GET ")
if replyNeeded:
s.send("/pythoneval?value=")
else:
s.send("/python?value=")
s.send(cmd)
s.send(" HTTP/1.1\r\n\r\n")
if replyNeeded:
reply = s.recv(5000)
s.close()
return reply

I am trying to use this method, but access VRED using VB .net. Below is a simplified version of the code I have tried. Eventually I plan to have two way communication with VRED, but for now I am just attempting to send a simple print command.

Imports System.Text
Imports System.IO
Imports System.Net.Sockets

Public Class Main

Private Sub GoButton_Click(sender As Object, e As EventArgs) Handles GoButton.Click

Dim sResp As String = SendVREDCmd("print 'Test'", False) '"getActiveCameraNode().getWorldTransform()", True)

End Sub

Private Const sServiceSite As String = "http://localhost:8888"
Private Const sContentType = "application/x-www-form-urlencoded"

Private Function SendVREDCmd(sPython As String, bReply As Boolean) As String

' Create byte array
Dim sPostData As String
If bReply Then
sPostData = "/pythoneval?value="
Else
sPostData = "/python?value="
End If
sPostData &= sPython
Dim byteArray As Byte() = Encoding.ASCII.GetBytes(sPostData)

' Mothod #1 - Socket
Dim oClient As New TcpClient(System.Net.Sockets.AddressFamily.InterNetwork)
oClient.Connect("localhost", 8888)
oClient.SendBufferSize = byteArray.Length
Dim oNetStream As NetworkStream = oClient.GetStream()
oNetStream.Write(byteArray, 0, byteArray.Length)
oNetStream.Flush()
oNetStream.Close()
oClient.Close()

' Mothod # 2 - Web Request - Post
Dim oReqPost As Net.WebRequest = Net.WebRequest.Create(sServiceSite)
oReqPost.Method = "POST"
oReqPost.ContentLength = byteArray.Length
Dim oStream As Stream = oReqPost.GetRequestStream()
oStream.Write(byteArray, 0, byteArray.Length)
oStream.Close()
oStream = Nothing

' Mothod #3 - Web Request - Get
Dim oReqGet As Net.WebRequest = Net.WebRequest.Create(sServiceSite & sPostData)
oReqGet.Method = "GET"
oReqGet.ContentType = sContentType
Dim oResp As Net.WebResponse = oReqGet.GetResponse()

Return ""

End Function

End Class

All 3 of the methods failed. The first two fail silently. The third method actually executes the python "print" command twice (printing "Test" twice in the terminal window) and errors out giving "The underlying connection was closed: The connection was closed unexpectedly."

Does anybody have any experience using the Web Interface for executing python scripts? I know this isn't a .net forum but maybe someone has tried something other than python.

Thanks for any help you can provide.

Re: Accessing Web Interface using VB .net

dan.husted — Thu, 21 Jun 2018 12:12:13 GMT

I solved my own problem. Revised VB .net code:

Imports System.Text
Imports System.IO
Imports System.Net.Sockets

Public Class Main

Private Sub GoButton_Click(sender As Object, e As EventArgs) Handles GoButton.Click

Dim sResp As String = SendVREDCmd("getActiveCameraNode().getWorldTransform()", True) '"print 'Test'"

If sResp IsNot Nothing Then Debug.Print(sResp)

End Sub

Private Const sPythonHead As String = "vred_python_result=["

Private Function SendVREDCmd(sPython As String, bReply As Boolean) As String

' Create stream byte array
Dim sPostData As String
If bReply Then
sPostData = "/pythoneval?value="
Else
sPostData = "/python?value="
End If
sPostData &= System.Net.WebUtility.UrlEncode(sPython)

Dim HTTP_string As String = "GET " & sPostData & " HTTP/1.1" & vbCrLf & vbCrLf
Dim encoding = New ASCIIEncoding()
Dim byteArray As Byte() = encoding.GetBytes(HTTP_string)

  ' Upload to vred
  Dim tcp As New TcpClient("localhost", 8888)
  Dim sReply As String = Nothing
  Dim tcp_stream As NetworkStream = tcp.GetStream()
  tcp_stream.Write(byteArray, 0, byteArray.Length)
  tcp_stream.Flush()
  If bReply Then

     ' Receive return data
     ReDim byteArray(10000)
     tcp_stream.Read(byteArray, 0, 10000)
     sReply = System.Text.Encoding.ASCII.GetString(byteArray)
     sReply = sReply.Substring(0, sReply.IndexOf(Chr(&H0)))
     If sReply.Contains(sPythonHead) Then
   sReply = sReply.Substring(sReply.IndexOf(sPythonHead) + sPythonHead.Length)
   sReply = sReply.Substring(0, sReply.Length - 1)
Else
   sReply = Nothing
End If
End If
tcp_stream.Close()
tcp_stream.Dispose()
tcp.Close()

Return sReply

End Function

End Class

Note that under the VRED Preferences for WebInterface "Enable Web Server" must be checked.

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Accessing Web Interface using VB .net

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