Threading - Object reference not set to an instance of an object

28 Feb 2006 4:17 PM

jay

Believe it or not...I am new to this side of development. I will try
to provide a little background on this app...I am calling this from an
aspx page. Feeding in the params and basically hoping to go out to the
servers specified in the xml files, run the command that I passed in
and return the output from the server. I was able to make this work
with a single thread and a single server. Now...it is time to beef it
up a bit...and multi-thread it. I haven't messed with threading much
in the past...and I am sure that someone will respond with "learn to
crawl before you learn to run." If life were that simple...

I continue to get the Object reference not set error when I call this
dll. It compiles fine...but, something is obviously not initializing
properly...and I am just missing it. I wrote a quick test function and
put it in the sshSearch Class and it worked fine...shich means that the
SearchNet function is NOT working fine. I would really appreciate ANY
help that ANYONE can provide. I have been researching this for about 2
weeks...including the purchase of a new book (dang things are
expensive) and just about every group that I can find.
Again...thanks!!! Jay

Imports System
Imports System.IO
Imports System.Web
Imports System.Xml
Imports System.Text
Imports System.Data
Imports System.Threading
Imports System.Diagnostics
Imports Microsoft.VisualBasic

Namespace SearchThis

Public Class sshSearch

Public allResults As String
Public strNow As String

Public Function SearchNet( strSearch As String,intLogLevel As Integer )
    Dim dtmNow As DateTime
    dtmNow = DateTime.Now()
    strNow = dtmNow.ToString("MMddyyyyhhmmss")
    Dim usrname As String
    usrname = "username"
    Dim pw As String
    pw = "password"

    Dim cfg As New XmlDataDocument
    Dim strServerGroup As String
    strServerGroup = "cbaa"
    If strServerGroup = "cbaa" Then
        cfg.Load( "d:\inetpub\wwwroot\HAT\bin\searchnet" & strServerGroup &
".config" )
    End If
    Dim ndList As XmlNodeList
    ndList = cfg.SelectNodes("//ServerMenuItemIpAddress")

    Dim nd As XmlNode
    Dim i As Integer
    Dim s(32) As ThreadData
    Dim t As Thread
    i = 0
    For Each nd in ndList
        Dim serverIpAddress As String
        serverIpAddress = nd.InnerText
        Dim strPlinkArguments As String
        strPlinkArguments = "-ssh -l " & usrname & " -pw " & pw & " " &
usrname & "@" & serverIpAddress & " -batch " & strSearch
        s(i) = New ThreadData
        s(i).strPlinkArguments = strPlinkArguments
        t = New Thread(AddressOf s(i).DoTheWork)
        t.Start()
        i = i + 1
    Next

    Dim j As Integer
    Dim allDone as Boolean
    Do Until allDone
        allDone = True
        For j = 0 to i - 1
            allDone = allDone And s(i).Done
        Next
    Loop

    For j = 0 to i - 1
        allResults = allResults + s(j).GetResults
    Next

    If intLogLevel = 1 Then
            Dim sw As New
StreamWriter("D:\inetpub\wwwroot\HAT\searchnetlogs\searchnet" & strNow
& ".txt")
            sw.write(allResults)
            sw.Close()
    End If

    Return allResults

End Function

End Class

Public Class ThreadData
    Public strPlinkArguments As String
    Public Done As Boolean
    Public searchText As String

    Public Sub DoTheWork()

        Dim sr As StreamReader
        Dim sb As New StringBuilder("")
        Dim input As Integer
        Dim proc As Process = New Process()
        proc.StartInfo.FileName = "d:\inetpub\wwwroot\HAT\bin\plink.exe"
        proc.StartInfo.Arguments = strPlinkArguments
        proc.StartInfo.UseShellExecute = False
        proc.StartInfo.RedirectStandardOutput = True
        proc.Start()
        sr = proc.StandardOutput
        input = sr.Read
        Do Until input = -1
        sb.Append(ChrW(input))
        input = sr.Read
        Loop

        searchText = sb.ToString

        sr.Close()
        proc.Close()
        Done = True

    End Sub

    Public Function GetResults()
        Return searchText
    End Function

End Class

End Namespace

28 Feb 2006 6:53 PM

Cor Ligthert [MVP]

jay,

Do you really want to make from a ASPNet application a multithreading one.

Don't forget that the ASPNET application is the middle tier for all your
users being active with that. If you don't screw up your server with adding
extra threading, you are probably doing it yourself.

Just my thought,

Cor

28 Feb 2006 7:42 PM

jay

The thought has crossed my mind...more from a coding perspective (i.e.
I have been unable to solve this coding issue) than from a performance
perspective. There are times when this application will need to
connect to 16-20 servers, run a command and return the results. The
server that this is running on is a multiple CPU server wch does allow
for a performance gain when it comes to threading. I appreciate the
heads up...but, I also know that in the end, the amount of connections
needed to be made will require some form of threading to be efficient.

J