receive https post (asp.net)

[Amoril]

I am currently developing an app that will post an XML file *(1 to
100MB+ in size) to an outside vendor application via HTTPS P*ost
(doing
this in a vb.net windows app). The vendor will then at some *later
date
post an updated return XML file to my webserver (asp.net). T*he
primary
problem I'm having is getting the posted stream to load in a*n
XMLDocument object. When trying to read the posted stream in*to the
XMLDocument the following error is kicked back from my webse*rver
(seen
by the vendor), "The remote server returned an error: (500) *Internal
Server Error." At minimum I want to make sure that the XML t*hey're
posting to me is well-formed so I don't need to load it into* an
XMLDocument object if there's another way to do it.
Also they're expecting to post their info to me via HTTPS, h*ow can I
set up my page so it's looking for credentials to be passed *along
with
the XML stream? I see how to send credentials to them using
System.Net.Netw orkCredential, but I don't see how accept cre*dentials
from the vendor when they post to me.
Code used to accept HTTP post from Vendor:
Dim str As Stream
Dim strmContent As String
Dim strLen As Integer
Dim strRead As Integer
'Request input stream from the poster
str = Request.InputSt ream
'Get the length of incoming string
strLen = str.Length
'make a Byte array the size of the stream
Dim strArr(strLen) As Byte
'read the stream into the array
strRead = str.Read(strArr , 0, strLen)
'the stream will be ASCII encoded
Dim ascii As ASCIIEncoding = New ASCIIEncoding
'Get ASCII into reg. string here
strmContent = ascii.GetString (strArr)
Dim doc As XmlDocument = New XmlDocument
doc.LoadXml(str mContent)
doc.Save("D:\te mp\test5.xml")
'Return Response to poster.
Response.Write( "some response")
Any suggestions on what I can do to fix this or possible res*ources
that
might help me out?
Thanks!