Testing Access Method using Sockets (SSH,TELNET)

I need to parse a list of IPaddresses and determin if they are using SSH (port 22) or telnet (port 23). The best way I can think to do this is by attempting to open a socket (not the full connection). If port 22 is refused it's not SSH, then try port 23. The big problem is that there are 5000 entries in this list and I can't wait for the default timeout for each socket to determine the access method. That would be a total of 10,000 connection attempts and a complete waste of the users day!

Any help would be greatly appreciated.

P.S. I'm using VB 2005

Here's what I have so far...It always comes back as Telnet though.

VB Code:

For Z = 1 To NumRows
            ProgressBar2.Value = Z
            ipaddr = Hostlist(Z, 0)
            System.Windows.Forms.Application.DoEvents()
 
            Try
                Using tcpClient
 
                    tcpClient.Connect(ipaddr, 23)
                    ProgressBar1.Value = 1
                    isConnected = tcpClient.Connected
                    tcpclient.close
                End Using
 
            Catch ex As Exception
 
            End Try
 
 
 
 
            Select Case isConnected
 
                Case True
                    
                    Hostlist(Z, 2) = "Telnet"
                Case False
                    ProgressBar1.Value = 2
                    Try
                        Using tcpClient
                            tcpClient.Connect(ipaddr, 22)
                            ProgressBar1.Value = 1
                            isConnected = tcpClient.Connected
                tcpclient.close
                        End Using
 
                    Catch ex As Exception
 
                    End Try
 
                    If isConnected = True Then
                        
                        Hostlist(Z, 2) = "SSH"
                    Else : Hostlist(Z, 2) = "ERR"
                    End If
 
            End Select
 
 
        Next

I find it hard to believe that nobody has the skills to solve this problem. Is there another reason there are no responses?

Your code is the reverse of your stated goal. The code first checks to see if the server accepts a telnet connection. If it does, whether the server accepts a SSH connection or not, the code says it's telnet. Try changing your code to match your goal.

As far as the time it takes to run through 5,000 addresses, that's how long it's going to take. You can't make 60 minutes take less than an hour, and you can't make 5,000 timeouts happen in less than 5,000 * <the time of one timeout>.

Thanks for the response.

Actually, if you look at it, it tries telnet, if it connects then it calls it telnet. If it doesn't connect, it tries ssh. If ssh succeeds, it calls it ssh. The problem turned out to be that I wasn't assigning isConnected = "" so on the next iteration of the loop, it already thought it was connected and therefore everyting else after that was deemed to be telnet. I'll paste in my current working code. As for the hour taking less than an hour. Well I don't agree with you. First, there could be some code optimization that would make the routine faster. Secondly, the answer for making 60min = 30min lies in multithreading. I plan to implement that sometime in the next few weeks.

Also, on our network the devices are either telnet with SSH disabled or SSH with Telnet disabled, so there's no reason to continue if the device responds to Telnet.

In addition, You'd be correct about not being able to change the time it takes to iterate through 5000 timeouts * 20seconds (the default) if you simply relied on default timeouts. I managed to speed things up significantly by pinging the device first using a 500 millisecond timeout (since there's no way to change the TCP Connect timeout). If the device doesn't respond, I assume it's dead and move to the next without ever trying to connect to it, so I've just reduced the time from 20 seconds to 1/2 second.

And for those who care (and there weren't many) here is the code that works. I hope that someone having similar issues in future finds it useful:

vb Code:

Friend Sub ParseList()
        Dim Hostlist(10000, 2) As String
        Dim temp, Path As String
        Dim CurrentField As String
        Dim CurrentRow As String()
        Dim X, Y, NumRows, Z As Integer
        Dim tcpClient As New System.Net.Sockets.TcpClient()
        Dim isConnected, HostAvailable As Boolean
        Dim ipaddr As String
 
 
 
        With ProgressBar2
 
            .Show()
            .Style = ProgressBarStyle.Continuous
            .Minimum = 0
            .Maximum = 10000
            .Value = 0
 
        End With
 
        Path = App_Path()
 
 
        Using HostReader As FileIO.TextFieldParser = My.Computer.FileSystem.OpenTextFieldParser(Path & "hostlist.txt")
 
            HostReader.SetDelimiters(vbTab)
 
            While Not HostReader.EndOfData
 
                temp = HostReader.ReadFields.ToString
                X = X + 1
                ProgressBar2.Value = X
                System.Windows.Forms.Application.DoEvents()
                NumRows = X
 
            End While
 
 
        End Using
 
        ProgressBar2.Hide()
 
        ReDim Hostlist(X, 2)
 
        X = 0
        Y = 0
 
 
        With ProgressBar2
 
            .Show()
            .Style = ProgressBarStyle.Continuous
            .Minimum = 0
            .Maximum = 10000
            .Value = 0
 
        End With
 
        Using HostReader As FileIO.TextFieldParser = My.Computer.FileSystem.OpenTextFieldParser(Path & "hostlist.txt")
 
            HostReader.TextFieldType = FileIO.FieldType.Delimited
            HostReader.SetDelimiters(vbTab)
 
            While Not HostReader.EndOfData
 
                CurrentRow = HostReader.ReadFields
 
                For Each CurrentField In CurrentRow
 
                    Hostlist(X, Y) = CurrentField
                    Y += 1
 
                Next
 
                X += 1
                Y = 0
                ProgressBar2.Value = X
                System.Windows.Forms.Application.DoEvents()
            End While
 
        End Using
        PictureBox2.Show()
        ProgressBar2.Value = 0
 
        X = 0
        Y = 0
 
        With ProgressBar2
 
            .Show()
            .Style = ProgressBarStyle.Continuous
            .Minimum = 0
            .Maximum = NumRows
            .Value = 0
 
        End With
 
        With ProgressBar1
 
            .Show()
            .Style = ProgressBarStyle.Continuous
            .Minimum = 0
            .Maximum = 2
            .Value = 0
 
        End With
 
        Label1.Visible = True
        Label2.Visible = True
 
        For Z = 1 To NumRows
            ProgressBar2.Value = Z
            ipaddr = Hostlist(Z, 0)
            Label2.Text = "Currently Processing:  " & Z.ToString & " of " & NumRows.ToString
            System.Windows.Forms.Application.DoEvents()
 
            Try
                HostAvailable = My.Computer.Network.Ping(ipaddr, 500)
            Catch ex As Exception
 
            End Try
 
            If HostAvailable = True Then
                Try
                    Using tcpClients As New TcpClient
                        Label1.Text = "Trying: " & ipaddr & " On " & "Port 23"
                        ProgressBar1.Value = 2
                        System.Windows.Forms.Application.DoEvents()
                        tcpClients.Connect(ipaddr, 23)
 
                        isConnected = tcpClients.Connected
                        System.Windows.Forms.Application.DoEvents()
 
                    End Using
 
                Catch ex As Exception
                    Select Case Err.Number
                        Case 5
                            isConnected = False
                        Case Else
                            MsgBox(Err.Number)
                    End Select
 
                End Try
 
 
 
 
                Select Case isConnected
 
                    Case True
                        Hostlist(Z, 2) = "Telnet"
                        ProgressBar1.Value = 0
 
                    Case False
                        ProgressBar1.Value = 2
                        Try
                            Using TcpClients As New TcpClient
                                Label1.Text = "Trying: " & ipaddr & " On " & "Port 22"
                                ProgressBar1.Value = 2
                                System.Windows.Forms.Application.DoEvents()
                                TcpClients.Connect(ipaddr, 22)
                                isConnected = TcpClients.Connected
                                System.Windows.Forms.Application.DoEvents()
 
                            End Using
 
                        Catch ex As Exception
                            Select Case Err.Number
                                Case 5
                                    isConnected = False
                                Case Else
                                    MsgBox(Err.Number)
                            End Select
 
                        End Try
 
                        If isConnected = True Then
 
                            Hostlist(Z, 2) = "SSH"
                            isConnected = Nothing
 
                        Else : Hostlist(Z, 2) = "ERR"
                        End If
 
                End Select
 
 
            End If
            'Debug.Print(Z & "  " & Hostlist(Z, 0) & "  " & Hostlist(Z, 2))
        Next
 
        PictureBox3.Show()
        System.Windows.Forms.Application.DoEvents()
 
       
    End Sub