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Hi,
I'm currently developping an internet hotspot. This hotspot is connected to the internet by a cell-phone modem. Since this solution is used on passenger ships trough Europe, sometimes there is no connection to the internet. When this is the case, the hotspots clients will receive 'page cannot be displayed' errors. (the client can't reach the DNS server on the internet).
Right now I'm researching the possibility to write a DNS server, which normaly should forward all incomming request to another (internet) DNS server and return them to my clients. ONLY if there is no response from the forwarding DNS server, my DNS server should return a default address. On this address I will configure a webpage informing the clients about the current connection status.
If anybody has suggestions about this I would be glad to hear them.
Thanks in advance!
Kind regards,
Tom
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You don't need your own DNS server. A Proxy server could do this though. Just about anything off-the-shelf would work and let you configure the error page.
Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007
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Thank you for your reaction.
I'm aware of the possibilities of using a proxy server. The first version of my solution was in fact based on a proxy server. But there is one major problem with that approach. Since the clients are unknown users, I need to redirect them to a page where they can log in. Only after this, they are allowed to use the Internet. (the system is based on a radius server for authentication and accounting.) As far as I know, this isn't possible with a proxy server.
Authentication isn't a problem at all when using a proxy server, it is the redirection part that is quite hard to accomplish WITHOUT installing a proxy client or something like that.
It is my intention to have the clients use this hotspot without the need to install any software or having to make changes to their settings.
In fact, I have accomplished that part to my satisfaction. The only problem that remains is the problem that I described in my first post.
I think I need a multithreading server and a DNS component to reach my goal. In fact, all I want to do is forward all incomming DNS queries and return them to my clients. I only want to send a custom address when the forwarding server is unreachable.
Do you know of any project that is usable as a basis for this? I already found a DNS component for queriyng servers, but I still need something to listen / answer DNS requests.
Any comment would be usefull and appreciated.
Kind regards,
Tom.
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TomPanjer1974 wrote: it is the redirection part that is quite hard to accomplish WITHOUT installing a proxy client or something like that.
What client? This is stuff that's built into every web browser already. You don't need a client, just the configuration.
TomPanjer1974 wrote: In fact, all I want to do is forward all incomming DNS queries and return them to my clients. I only want to send a custom address when the forwarding server is unreachable.
DNS servers already do this. but, they'll cache the fesults and pass the cached versions to the client if the upstream DNS isn't available. Now you run into the same problem. The DNS server doesn't care that the web page isn't available, but a proxy server does. Thats why i said this could be done using the proxy. If the page isn't available, it'll send down either a standard 400 or 500 error page or a custom one which you supply, like your status page.
Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007
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Is it possible to automaticly configure an anonymous client's webbrowser to use a proxy server?
Dave Kreskowiak wrote: DNS servers already do this. but, they'll cache the fesults and pass the cached versions to the client if the upstream DNS isn't available
I know. That's why I'm still thinking of building my own DNS server, so I can controll the way it give's answers to my clients. No caching, just forwarding all the queries.
I realy appreciate your suggestions, it's just that I want to offer a solution where my clients do not need to change any settings. And as I sayd before: I don't know of a way to configure my clients webbrowsers to use a proxy server, while pointing them to a diffrent DNS server is easy enough.
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TomPanjer1974 wrote: Is it possible to automaticly configure an anonymous client's webbrowser to use a proxy server?
Nope, and you don't have to.
You also don't have to write a DNS server to do this either.
I don't know exactly how it's done, but do some research into how Internet server works in a hotel. If you connect to the wireless network in a hotel and request a page, the first page you get is a login page for charges or some other "Welcome to Holiday Inn" page or some garbage like that.
Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007
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Hi Dave,
Thanks again for your response.
Dave Kreskowiak wrote: I don't know exactly how it's done, but do some research into how Internet server works in a hotel. If you connect to the wireless network in a hotel and request a page, the first page you get is a login page for charges or some other "Welcome to Holiday Inn" page or some garbage like that.
That's exactly what I did some months ago. There are several programs available to do this, and in fact I'm using one. The only problem is, that ALL these hotspot programs depend on a normal internet connection, which isn't supose to fail. In my case, my internet connection is cell-phone based and therefore not as reliable as an xDSL line for example.
The software i'm currently using takes care of the redirection part. As soon as my clients connect to one of my accespoints, they are provided with an IP address, subnetmask, gateway and dns server. The gateway is my hotspot server which redirects my clients as soon as they try to access the internet. They get redirected to my authentication page. As soon as they are authenticated, there mac address is allowed in the radius server and off they go.
Again, this solution works perfect (in fact it does on a 100 or so locations) as long as the internet connection doesn't fail.
So I would like to thank you again for your comments, but I realy would like some help with building my custom DNS server. On this website I have found an article by Xiangyang Liu
called "A Simple .NET TCP Socket Component". In your opinion, is this usefull for what I'm trying to accomplish? I would like to use it as basis for my server, but I can't get it to work...
Looking forward to hear from you again!
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Please respond only if you can complete this assignment immediately! I need to create a name list program using parallel arrays. The first array lists names and the second array holds the gender of each person. There is an M for male names and an F for female names. I have created a list box (lstNames) and command buttons (cmdBoys, cmdGirls), but I need the code set so that the user will get a list of male names or female names in the list box. I've created the arrays, and put some code in but it's not working.
This is the code I wrote... well... the mess i've created
PLEASE any help greatly appreciated, but I'm just learning... please keep it simple!
' Declare and initialize the name array
Dim strNames() As String = {"John", "Paul", "Mary", "Jane", "Peter", "Sam", "Andrew", _
"Laura", "Juan", "Rachel", "Clifford", "Thomas", "Rebecca", "Susan", "Roberto", _
"Stefano", "Sara", "Jean", "Fred", "Roseann", "Alan", "Sally", "Dean", "Karen", "Carol"}
' Declare gender
Dim strGender() As String = {"M", "M", "F", "F", "M", "M", "M", "F", "M", "F", "M", "M", _
"F", "F", "M", "M", "F", "F", "M", "F", "M", "F", "M", "F", "F"}
Private Sub cmdBoys_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdBoys.Click
lstNames.Items.Clear()
'Declare an index variable
Dim intIndex As Integer
Dim intGender As Integer
'Set the index to the lower bound
intIndex = strNames.GetLowerBound(0)
'While the index is in range compare an element in the array with the search text
While ((intIndex < strNames.GetUpperBound(0)) And (strGender(intGender) = "M"))
intIndex += 1
End While
If strGender(intGender) = "M" Then
lstNames.Items.Add(strNames)
End If
End Sub
End Class
Laura
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laura h wrote: 'While the index is in range compare an element in the array with the search text
While ((intIndex < strNames.GetUpperBound(0)) And (strGender(intGender) = "M"))
intIndex += 1
End While
If strGender(intGender) = "M" Then
lstNames.Items.Add(strNames)
End If
There's so many problem with this, I don't know where to start other than the trash can. So, scrap everything from intIndex = strNames.GetLowerBound(0) down to End Sub.
I'm going to write any code for you because this screams "homework". What would you learn if I just wrote the code for you??
You need to create a loop than goes from the LowerBound, which you already have, to the Upperbound, which you already know how to get. You already have the variable that's going to track where you are in the arrays you're looking at, intIndex.
Inside this loop is where you check one index for the gender in every array position. If you find an M in the strGender array at the position indexed by intIndex, you just need to add the name from the strNames array to the ListBox, which you already know how to do.
When you get to the end of the loop, you're done. Oh! You don't need the intGender variable - get rid of it.
Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007
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This is my homework. I tried really hard to follow your instructions and you've helped immensly, but I'm still having trouble with one thing. I was able to make all of the names display, but I couldn't figure out how to get just the male names to display. Now I've got it displaying a place holder for each male name (instead of all names) but now it's not displaying the actual name. Here is what I have: But it just displays String[]Array instead of the name. I'm not sure how to fix it. Do you have time to help me? I've always figured out the code in the other assignments but this one has me pulling my hair out. Any help is greatly appreciated. 
Public Class Form1
' Declare and initialize the name array
Dim strNames() As String = {"John", "Paul", "Mary", "Jane", "Peter", "Sam", "Andrew", _
"Laura", "Juan", "Rachel", "Clifford", "Thomas", "Rebecca", "Susan", "Roberto", _
"Stefano", "Sara", "Jean", "Fred", "Roseann", "Alan", "Sally", "Dean", "Karen", "Carol"}
' Declare gender
Dim strGender() As String = {"M", "M", "F", "F", "M", "M", "M", "F", "M", "F", "M", "M", _
"F", "F", "M", "M", "F", "F", "M", "F", "M", "F", "M", "F", "F"}
Private Sub cmdBoys_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdBoys.Click
'Declare variable for boy names
Dim intIndex As Integer
'Set the index to the lower bound
intIndex = strNames.GetLowerBound(0)
'Display Boy names
For intIndex = 0 To strNames.GetUpperBound(0)
If strGender(intIndex) = "M" Then
lstNames.Items.Add(strNames)
End If
Next
End Sub
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I was able to figure it out. I know what piece I was missing. Thank you so much for your help. I appreciate you not writing the code, but just steering me in the right direction. I'll keep this site in mind for future assignments.
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laura h wrote: Please respond only if you can complete this assignment immediately
ROTFL - no-one is going to 'complete your assignment' for you.
Like Dave said, all of this sucks. Create a struct that contains the two bits of data you need, and a single array of the struct. If two pieces of data belong together, put them together.
Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
"I am working on a project that will convert a FORTRAN code to corresponding C++ code.I am not aware of FORTRAN syntax" ( spotted in the C++/CLI forum )
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just wondering if anyone knows y this wont work, i want to display the tables of the database selected in the next combo box and it gets stuck on "SQLDatabase = SQLServer.Databases.Item(cboDatabases.Text)" in the button2_click procedure , prob easy i no but brain not functioning, cheers
Option Strict Off
Option Explicit On
Friend Class Form1
Inherits System.Windows.Forms.Form
Public SQLServer As New SQLDMO.SQLServer
Dim SQLDatabase As SQLDMO.Database
'UPGRADE_WARNING: Event chkNTAuthentication.CheckStateChanged may fire when form is initialized. Click for more: 'ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?keyword="88B12AE1-6DE0-48A0-86F1-60C0686C026A"'
Private Sub chkNTAuthentication_CheckStateChanged(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles chkNTAuthentication.CheckStateChanged
' Enable Disable the Authentication dialog box ...
If chkNTAuthentication.CheckState = 1 Then
txtLogin.Enabled = False
txtPassword.Enabled = False
Else
txtLogin.Enabled = True
txtPassword.Enabled = True
End If
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim sqlApp As New SQLDMO.Application
Dim NameList As SQLDMO.NameList
Dim index As Integer
NameList = sqlApp.ListAvailableSQLServers
' Get the Servers on the network and display the Values into the combo
For index = 1 To NameList.Count
cboServer.Items.Add(NameList.Item(index))
Next
' Enable NT Auth by deafult.
If chkNTAuthentication.CheckState = 1 Then
txtLogin.Enabled = False
txtPassword.Enabled = False
End If
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim SQLServer As New SQLDMO.SQLServer
On Error GoTo ErrorHandler
SQLServer.LoginTimeout = 10
' Check for the type of authentication and Logon to the Server.
If chkNTAuthentication.CheckState Then
' For Integrated NT security
SQLServer.LoginSecure = True
SQLServer.Connect(cboServer.Text)
Else
' SQL Server security
SQLServer.Connect(cboServer.Text, txtLogin.Text, txtPassword.Text)
End If
cboDatabases.Visible = True
Label4.Visible = True
Button2.Visible = True
Dim db As SQLDMO.Database
cboDatabases.Items.Clear()
' Fill the database combobox
For Each db In SQLServer.Databases
If Not db.SystemObject Then
cboDatabases.Items.Add(db.Name)
End If
Next db
' Select the first database by default
cboDatabases.SelectedIndex = 0
Exit Sub
ErrorHandler:
MsgBox(Err.Description, MsgBoxStyle.Critical, "Error - Connecting")
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim tbl As SQLDMO.Table
Dim sp As SQLDMO.StoredProcedure
cboTables.Visible = True
Label5.Visible = True
' Get a reference to the selected database
SQLDatabase = SQLServer.Databases.Item(cboDatabases.Text)
' Fill the Tables combo
cboTables.Items.Clear()
cboTables.Items.Add("(none)")
cboTables.Items.Add("(all)")
' Fill all the table looping from the SQL Object
For Each tbl In SQLDatabase.Tables
If Not tbl.SystemObject Then
cboTables.Items.Add(tbl.Name)
End If
Next tbl
cboTables.SelectedIndex = 0
End Sub
End Class
gvm
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I have so far been using Using in the following way.
Using swOutputWriter as New StreamWriter(file, whatever)
swOutputWriter.Writeline(line)
End Using but today I saw the following
Dim swOutputWriter as StreamWriter
Using swOutputWriter
swOutputWriter.Writeline(line)
End Using Are both correct? If the 2nd is correct, is it also as safe?
CleaKO
"I think you'll be okay here, they have a thin candy shell. 'Surprised you didn't know that.'" - Tommy (Tommy Boy)
"Fill it up again! Fill it up again! Once it hits your lips, it's so good!" - Frank the Tank (Old School)
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There's actually a serious bug in the second example, but they boil down to exactly the same code:
Dim swOutputWriter As StreamWriter
swOutputWriter = New StreamWriter(file,whatever)
Using swOutputWriter
....
End Using
They are both correct and safe...
Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007
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Oh yes I missed the New portion.
Thanks...
One more though, if you create it a new instance of that object and then use the surrounding "Using/End Using" later, is that object now gone and will need to be re-instantiated?
-- modified at 12:25 Friday 20th April, 2007
CleaKO
"I think you'll be okay here, they have a thin candy shell. 'Surprised you didn't know that.'" - Tommy (Tommy Boy)
"Fill it up again! Fill it up again! Once it hits your lips, it's so good!" - Frank the Tank (Old School)
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Yep. The object that's specified on the Using line will automatically be Disposed when execution ever, for ANY reason, leaves the Using block. If you still need it beyond that, maybe you shouldn't be using Using, or you'll have to expand the scope of the Using block to encompass the code you need.
Using was put in so you didn't have to make absolutely sure you disposed an object in the event you forgot to or an error occured in your code, forcing it to take an execution path you didn't anticipate.
Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007
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what is max rows we can have on msflexgrid
Develop2Program & Program2Develop
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Theoretically, the maximum number is the maximum long value - 2,147,483,647.
In practice, it will depend on the resources available to you - I ran a quick test and was able to get 145,000 rows.
Tim
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The real question is why would you want to show that many? The scroll wheel on a mouse is only good for 5,000 miles.
Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007
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Hi,
I am using the following to redirect the output of a dos command to a richtextbox but anytime I try run it to get the directory listing of a large CD nothing happens but if there is only one file on the CD it works. Can anyone help.
Dim myProcess As Process = New Process
Dim prgOutput As String ' Output from DOS program
myProcess.StartInfo.FileName = "c:\dir.bat" 'Full pathname to including file name
myProcess.StartInfo.CreateNoWindow = True ' Does not create a window DOS program
myProcess.StartInfo.UseShellExecute = False ' Must be false to redirect output
myProcess.StartInfo.RedirectStandardOutput = True
myProcess.Start() ' Start the DOS program
myProcess.WaitForExit() ' Wait until it completes before moving on
prgOutput = myProcess.StandardOutput.ReadToEnd ' Get the DOS output
rtbOutput.Text = prgOutput
I am using a .bat file which has the following commands:
@ECHO OFF
d:
dir /A /S /O:GNE
c:
Running the .bat file directly from the command prompt works on the disc with loads of files
Thanks
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johnjsm wrote: myProcess.WaitForExit() ' Wait until it completes before moving on
prgOutput = myProcess.StandardOutput.ReadToEnd ' Get the DOS output
Try changing the order of these two lines
Cheers,
Suresh
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I did what you suggested and it works. Thnaks for your help.
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Just got VB 2005 and wonder, How do you add code snippets to the list.
Also can anyone recommend any web sites for code snippets?
Thanks
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