Visual Basic

capture packet and manipulate fields

4-May-04 4:41

This is because IDList.ToArray() is returning an Array object and not an Object(). You might want to remove the GetType(Int32) and try it. But I think it's still going to fail. The problem your running into is an ArrayList is a general type collection, not an Object(). It can hold any type of data without being cast to a specific type first. You can create an ArrayList without any parameters and just start adding Strings to it and it won't complain. Same is true for Integers...if you just create the ArrayList and start adding numbers to it, chances are that ArrayList is a collection of Integers and not Int32s. This is were your casting problem is coming from. Your trying to do two cast's, an Integer to an Int32, and an Array to an Object(), under the Strict rules.

You either have to use the ArrayList as is, or use an Object() array instead of an ArrayList (consistancy of object types is key!), or get rid of the Option Strict.

Personally, I never use Option Strict...

RageInTheMachine9532

babur khan3-May-04 23:31

babur khan

3-May-04 23:31

Can anyone please tell me how to capture the packet in vb.net(code)in windows and how to program to manipulate the data field of the TCP and UDP packets. i have no idea about it. just tell me from the begining. should i have to do the SDK or device driver programming. so where to start.i really need help these days so i am looking forward to you people for some tips.

Colin Angus Mackay4-May-04 0:33

4-May-04 0:33

I'm trying to understand what you are trying to do.

1. Capture a packet.
2. Modify the data in that TCP or UDP packet.
3. Send the modified packet on its way.

Is this correct?

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

Coming soon: The Second EuroCPian Event

babur khan4-May-04 5:25

babur khan

4-May-04 5:25

yeah correct i want to do the same thing actually i want to make my encryption algorithm and apply on the data field of the UDP and TCP packets in wireless packets. can you tell me or guide me stepwise what should i do . main thing is that i want to do it in vb.net. lookiing forward to you.

Colin Angus Mackay4-May-04 6:21

4-May-04 6:21

The obvious question is why don't you encrypt the packets at source rather than in transit? (by "in transit" I mean that after the process that is sending the packets has created the packet but before the packet has left the PC) I am assuming that you did not create the process that is sending or receiving the data.

I think what you need to look at is something like an NDIS hook - which is effectively a kernel mode device driver that hooks into the network layer just as the packets are entering/leaving the PC. There is a solution out there that will allow you to create such a hook and pass it into something that isn't a kernel mode process (like VB.NET). However, I don't recall what it is called off the top of my head. (I'll get back to you on that). If you don't want to use that solution then I think you are going to have to create your own kernel mode device driver which most definitely cannot be written in VB.NET.

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

Coming soon: The Second EuroCPian Event

Dave Kreskowiak4-May-04 9:18

4-May-04 9:18

What your thinking of is an NDIS Intermediate Driver. These things slide in between the miniport and protocol drivers.

For original poster:
Docs on NDIS Intermediate drivers start here[^]. Your best best is to write the NDIS driver in C++. That'll save you time of recoding all of the structures, constants and function headers. You'll be doing this for about 3 dozen functions and structures. On top of that, you'll have a VERY difficult time debugging this thing unless your up to speed on debugging kernel mode drivers...

RageInTheMachine9532

Colin Angus Mackay4-May-04 9:29

4-May-04 9:29

Dave Kreskowiak wrote:
What your thinking of is an NDIS Intermediate Driver

Almost, what I was thinking of was an NDIS Filter Hook Driver[^]

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

Coming soon: The Second EuroCPian Event

babur khan4-May-04 23:03

babur khan

4-May-04 23:03

i cant understand you what are you saying, you mean that
i should NDIS hook , take its output to manipulate data field of TCP and then again pass this information to the driver? where should i write the code in vb.net which will do the work? is this or else?
can you briefly explain the steps involving in this thing?
and can you refer me some tutorials?
anyways thanks i seached on the google and found some sites on ndis.
waiting...

Colin Angus Mackay4-May-04 23:32

4-May-04 23:32

babur khan wrote:
you mean that
i should NDIS hook , take its output to manipulate data field of TCP and then again pass this information to the driver?

If you are not generating the packets in the first place then yes - The wording of your previous posts indicates that this is the case. If you are generating the packets there are easier solutions open to you.

babur khan wrote:
where should i write the code in vb.net which will do the work?

It is not something that VB.NET can do by itself, you will need a third party piece of software. NTKernel[^] produce a product called WinPKFilter[^] which might suit your needs.

To connect it to VB.NET you will need to P/Invoke the functions that you are interested in.

babur khan wrote:
and can you refer me some tutorials?

The web site, has a forum for its products and demo software to show how to build applications using its components.

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

Coming soon: The Second EuroCPian Event

Dave Kreskowiak4-May-04 4:24

4-May-04 4:24

babur khan wrote:
i have no idea about it. just tell me from the begining.

In the beginning, there were dinosaurs! Then they all died...;P

Packet capturing is not so simple that someone could explain everything about it here. It's just too big a topic. But there is a couple of articles on it here[^] and here[^] on CodeProject. There are also some packet capture libraries out there like this one[^]. It amazing what you can find with a Google search on "source code packet capture"!

RageInTheMachine9532

Colin Angus Mackay4-May-04 4:33

4-May-04 4:33

Dave Kreskowiak wrote:
In the beginning, there were dinosaurs! Then they all died

Airplane? (or Airplane II?)

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

Coming soon: The Second EuroCPian Event

Dave Kreskowiak4-May-04 4:42

ComboBox doesn't show last item added (but does when I use debugger)

4-May-04 4:42

I think it was Airplane! Laugh | :laugh:

RageInTheMachine9532

Rikard Skarp3-May-04 22:34

Rikard Skarp

3-May-04 22:34

Hi. I'm a newbie programmer so my problem probably have an easy solution.
Here's the code that adds items to my ComboBox:

*****************************************************'
Sub loadTypCombo()
Dim recset As New ADODB.Recordset
Dim conn As ADODB.Connection
Set conn = loadDatabase(CommonDialog1.FileName)

recset.CursorType = adOpenDynamic
recset.LockType = adLockOptimistic
Set recset.ActiveConnection = conn

recset.Open "SELECT * FROM tblObjects ORDER BY Name"
While Not recset.EOF
TypCombo.AddItem (recset("name"))
recset.MoveNext
Wend
recset.Close
Set recset = Nothing
conn.Close
Set conn = Nothing
End Sub
******************************************************

The problem I have is when I run the program only 4 of the 5 records in tblObjects are added to my ComboBox, however, when I debug all 5 are added and it works like it's supposed to.

How can I fix this?

Thanks in advance, Rikard

is it a modifier problem?

3hrguy3-May-04 22:26

3hrguy

3-May-04 22:26

i have a form allows me to add, edit, delete records, and also see the master list of my records, this form has a dataset and a winsock-like object (private withevents) this application is connected to a server using my winsock-like object

what it does is that everytime i click on add or edit, a new form is instantiated and the record which i want to edit from the previous form is loaded in this new form (in the case of add, no data is loaded on the form) after adding or making the changes, the new form calls the add record method / edit record method to...

1. update the changes to the database
2. pass the new data to the server using my winsock-like object

after executing, the new form closes itself. i don't have any problems with updating changes to the database, but when i try to send the new data thru my winsock-like object, it gives me a "object reference not set..." error where in fact i clearly created a new instance of my winsock class when the form was loaded and the connection is still alive between my application and the server, should i change the modifier of my winsock-like object from private to shared or protected? please tell me what went wrong, thanks

Re: is it a modifier problem?

Dave Kreskowiak4-May-04 4:15