Hi Folks,

I got a weird problem, I create an XMLWriter to post a document via the
webrequest stream and after running a network trace, I notice the data
is prefixed with 3 invalid characters!

The invalid characters are:   ef bb bf, at the top of the stream, which
are . Why is this occuring, I am totally baffled by this?

Here is the stream:
000000A5  ef bb bf 3c 3f 78 6d 6c  20 76 65 72 73 69 6f 6e ...<?xml
version
000000B5  3d 22 31 2e 30 22 20 65  6e 63 6f 64 69 6e 67 3d ="1.0" e
ncoding=
000000C5  22 75 74 66 2d 38 22 3f  3e 3c 54 43 4e 5f 52 65 "utf-8"?
000000D5  63 65 69 70 74 20 78 6d  6c 6e 73 3d 22 75 72 6e ceipt xm
lns="urn
000000E5  3a 65 75 2e 63 65 63 2e  74 72 65 6e 2e 74 63 6e :eu.cec.
tren.tcn
000000F5  22 3e 3c 48 65 61 64 65  72 20 56 65 72 73 69 6f "><Heade r
Versio
00000105  6e 3d 22 31 2e 34 22 20  54 65 73 74 49 64 3d 22 n="1.4"
TestId="
00000115  54 65 73 74 49 64 5f 31  22 20 4d 53 52 65 66 49 TestId_1 "
MSRefI
00000125  64 3d 22 4d 53 52 65 66  49 64 5f 31 22 20 54 43 d="MSRef
Id_1" TC
00000135  4e 52 65 66 49 64 3d 22  30 30 30 30 30 30 30 30 NRefId="
00000000
00000145  2d 30 30 30 30 2d 30 30  30 30 2d 30 30 30 30 2d -0000-00
00-0000-
00000155  30 30 30 30 30 30 30 30  30 30 30 30 22 20 53 65 00000000
0000" Se
00000165  6e 74 41 74 3d 22 31 39  39 39 2d 30 39 2d 30 39 ntAt="19
99-09-09
00000175  54 30 30 3a 30 30 3a 30  30 2d 30 30 3a 30 30 22 T00:00:0
0-00:00"
00000185  20 46 72 6f 6d 3d 22 55  6e 6b 6e 6f 77 6e 22 20  From="U
nknown"
00000195  54 6f 3d 22 55 6e 6b 6e  6f 77 6e 22 20 53 74 61 To="Unkn
own" Sta
000001A5  74 75 73 43 6f 64 65 3d  22 4f 4b 22 20 53 74 61 tusCode=
"OK" Sta
000001B5  74 75 73 4d 65 73 73 61  67 65 3d 22 54 68 69 73 tusMessa
ge="This
000001C5  20 69 73 20 61 20 6d 65  73 73 61 67 65 20 73 65  is a me
ssage se
000001D5  6e 74 20 61 75 74 6f 6d  61 74 69 63 61 6c 6c 79 nt autom
atically
000001E5  20 62 79 20 74 68 65 20  54 43 4e 20 70 72 6f 62  by the  TCN
prob
000001F5  65 20 74 6f 6f 6c 2c 20  70 6c 65 61 73 65 20 69 e tool,
please i
00000205  67 6e 6f 72 65 20 69 74  2c 20 74 68 61 6e 6b 73 gnore it ,
thanks
00000215  22 3e 3c 2f 48 65 61 64  65 72 3e 3c 2f 54 43 4e "></Head
er></TCN
00000225  5f 52 65 63 65 69 70 74  3e                      _Receipt >



Here is the code:
Imports System.Security.Cryptography.X509Certificates
Imports System.Net
Imports System.Net.Security
Imports System.Xml
Imports System.Security.Policy 'Important for SSL validation checks


Public Class HTTPPost

    Dim cName As String
    Dim wReq As HttpWebRequest
    Dim wResp As WebResponse
    Dim xmlWriter As XmlTextWriter
    Dim timeNow As DateTime
    Dim interval As Double
    Dim xmlDoc As New XmlDocument
    Dim httpCode As String
    Dim statusMessage As String
    Dim secondsToComplete As String
    Dim DataWriter As New DataWriter
    Dim c_url As String
    Dim email As New Email
    Dim _emailTable As TachonetPingDataSet.EmailDataTable


    Public Sub GenerateXML(ByVal countryTable As
TachonetPing_Con.TachonetPingDataSet.CountryDataTable, ByVal emailTable
As TachonetPing_Con.TachonetPingDataSet.EmailDataTable, ByVal
NetworkTimeoutMilliseconds As Integer)
        _emailTable = emailTable
        Dim cert As X509Certificate =
X509Certificate.CreateFromCertFile(My.Settings.ClientCertificatePath)
        For Each dr As TachonetPing_Con.TachonetPingDataSet.CountryRow
In countryTable
            If Not dr(2) Is System.DBNull.Value Then
                Dim xmlString As String = TCNReceipt.CreateXML("TCN_" &
dr(0))
                SendXML(dr(1), dr(2), xmlString, cert,
NetworkTimeoutMilliseconds, emailTable)
            End If

        Next
    End Sub

    Private Function SendXML(ByVal countryName As String, ByVal url As
String, ByVal xmlText As String, ByVal cert As X509Certificate, ByVal
NetworkTimeoutMilliseconds As Integer, ByVal emailTable As
TachonetPing_Con.TachonetPingDataSet.EmailDataTable) As Boolean
        Try
            cName = countryName
            c_url = url
            xmlDoc.LoadXml(xmlText)
            'Setup the delegate with the address of the handling
function for certificate validation.
            ServicePointManager.ServerCertificateValidationCallback =
New RemoteCertificateValidationCallback(AddressOf MyCertValidationCb)
            timeNow = Date.Now 'Get the time which will be used by
exceptions
            wReq = HttpWebRequest.Create(url) ' Connect to URL
            wReq.ClientCertificates.Add(cert)
            wReq.Timeout = NetworkTimeoutMilliseconds

            wReq.Method = "POST" 'Set HTTP Method
            wReq.ContentType = "text/xml charset=utf-8" ' Set Content
Type
            'Open Stream
            xmlWriter = New XmlTextWriter(wReq.GetRequestStream(),
System.Text.Encoding.UTF8)
            'Send the XML Data
            xmlDoc.WriteTo(xmlWriter)
            xmlWriter.Close()

            'Get Response Stream
            timeNow = Date.Now 'If an exception did not occur, grab the
time here
            wResp = wReq.GetResponse
            If TypeOf wResp Is HttpWebResponse Then
                httpCode = CType(wResp, HttpWebResponse).StatusCode
'Convert to HTTPWebResponse
                If httpCode = HttpStatusCode.Accepted Or httpCode =
HttpStatusCode.OK Then
                    interval = Date.Now.Subtract(timeNow).TotalSeconds
                    secondsToComplete = interval.ToString("f3")
                    statusMessage = "UP - Response Time: " &
secondsToComplete & " milliseconds"
                    DataWriter.UpdateAlertTracker(Date.Now,
countryName, statusMessage)
                Else
                    statusMessage = "Down - HTTP Code: " & httpCode
                    DataWriter.UpdateAlertTracker(Date.Now,
countryName, statusMessage)
                    WindowsEventLogger.LogMessageWarning(countryName &
": " & statusMessage & vbNewLine & "HTTPCode: " & httpCode)
                    email.SendEmail(cName, httpCode, emailTable)
                End If
            End If
            wResp.Close()

        Catch wex As WebException
            If Not CType(wex.Response, Net.HttpWebResponse) Is Nothing
Then
                httpCode = CType(wex.Response,
Net.HttpWebResponse).StatusCode
                statusMessage = "Down - HTTP Code: " & httpCode
                DataWriter.UpdateAlertTracker(Date.Now, countryName,
statusMessage)
                WindowsEventLogger.LogMessageWarning(countryName & ": "
& statusMessage & vbNewLine & "HTTPCode: " & httpCode)
                email.SendEmail(cName, "httpCode: " & httpCode,
emailTable)
            Else
                httpCode = "n/a"
                statusMessage = wex.Message
                statusMessage = "Down: " & wex.Message
                DataWriter.UpdateAlertTracker(Date.Now, countryName,
statusMessage)
                WindowsEventLogger.LogMessageWarning(countryName & ": "
& statusMessage & vbNewLine & "HTTPCode: " & httpCode)
                email.SendEmail(cName, "httpCode: " & httpCode,
emailTable)
            End If

        Catch ex As Exception
            statusMessage = ex.Message
            httpCode = "n/a"
            DataWriter.UpdateAlertTracker(Date.Now, countryName,
statusMessage)
            WindowsEventLogger.LogMessageCritical(countryName & ": " &
statusMessage & vbNewLine & "HTTPCode: " & httpCode)
            Throw
        Finally
            If Not xmlWriter Is Nothing Then
                xmlWriter.Close()
            End If
            If Not wResp Is Nothing Then
                wResp.Close()
            End If
        End Try
    End Function

    Public Function MyCertValidationCb(ByVal sender As Object, ByVal
certificate As X509Certificate, ByVal chain As X509Chain, ByVal
sslPolicyErrors As SslPolicyErrors) As Boolean

        If sslPolicyErrors =
Security.SslPolicyErrors.RemoteCertificateChainErrors Then
            WindowsEventLogger.LogMessageWarning(cName & ": Remote
Certificate Chain Error" & vbNewLine & c_url)
            email.SendEmail(cName, "Certificate Error: Remote
Certificate Chain Error", _emailTable)
            Return False
        ElseIf sslPolicyErrors =
sslPolicyErrors.RemoteCertificateNameMismatch Then
            Dim z As Zone
            z = Zone.CreateFromUrl(CType(sender,
HttpWebRequest).RequestUri.ToString())
            If (z.SecurityZone = System.Security.SecurityZone.Intranet
Or z.SecurityZone = System.Security.SecurityZone.MyComputer) Then
                Return True
            Else
                WindowsEventLogger.LogMessageWarning(cName & ": Remote
Certificate Name Mismatch" & vbNewLine & c_url)
                email.SendEmail(cName, "Certificate Error: Remote
Certificate Name Mismatch", _emailTable)
                Return False
            End If
        ElseIf sslPolicyErrors =
sslPolicyErrors.RemoteCertificateNotAvailable Then
            WindowsEventLogger.LogMessageWarning(cName & ": Remote
Certificate not available" & vbNewLine & c_url)
            email.SendEmail(cName, "Certificate Error: Remote
Certificate not available", _emailTable)
            Return False
        ElseIf sslPolicyErrors = sslPolicyErrors.None Then
            Return True
        End If
    End Function
End Class

Thus wrote romiko2***@yahoo.co.uk,

These are not "invalid characters". It's the UTF-8 byte order mark (BOM).

To omit it, change

xmlWriter = New XmlTextWriter(wReq.GetRequestStream(),
System.Text.Encoding.UTF8)

to

' Don't trust me writing proper VB .NET code ;-)
Dim Encoding utf8 as Encoding
utf8 = New UTF8Encoding()
xmlWriter = New XmlTextWriter(wReq.GetRequestStream(), utf8)

The default instance System.Text.Encoding.UTF8 prepends a BOM, but if you
create your own UTF8Encoding instance, you can change this behaviour.

Cheers,

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