How to communicate with Win CE device connected by usb - .NET (Core and Framework) Discussion Boards

Broadcasting custom windows message(Interprocess communication)

callousfantom7-Aug-09 2:17

7-Aug-09 2:17

Hi I have a service written in Visual C++ 6 that needs to interact with an application written in vb.net. In my service I have used :

DWORD mymsg=RegisterWindowMessage("my_message")

to register a unique custom message.
I then use:

BOOL b=SendNotifyMessage(HWND_BROADCAST,mymsg,NULL,NULL)

to broadcast my message. However, I can't seem to be able to capture this message in the Windowproc function of my vb.net application.

Private Declare Function RegisterWindowMessage Lib "user32" Alias "RegisterWindowMessageA" (ByVal lpString As String) As Integer
Dim mymsg As Integer = RegisterWindowMessage("my_message")

Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
if m.Msg=mymsg then
--do something--
end if
end sub

Please help! Sigh | :sigh:

P.S.:I need to show a pop up in my .net application when it receives this message. The message values have all registered properly in both applications and are returned to be the same when I print them. Also the SendNotitfyMessage in my service returns a non zero value(supposed to indicate success). What do I do?? What am I doing wrong? Is there something wrong with my message receiving code in vb.net?

Re: Broadcasting custom windows message(Interprocess communication)

Moreno Airoldi7-Aug-09 2:45

Moreno Airoldi

7-Aug-09 2:45

Try changing your WndProc declaration to:

<System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
Protected Overrides Sub WndProc(ByRef m As Message)

2+2=5 for very large amounts of 2
(always loved that one hehe!)

Re: Broadcasting custom windows message(Interprocess communication)

callousfantom9-Aug-09 18:43

callousfantom

9-Aug-09 18:43

Thanks for the suggestion but I tried it and it didn't really work. I don't think it's a security issue. I doubt that.

Re: Broadcasting custom windows message(Interprocess communication)

Moreno Airoldi9-Aug-09 22:46

Moreno Airoldi

9-Aug-09 22:46

Erm I just read your post again and see you are talking about a "service". If you mean a windows system service, then what Mark said is right: you shouldn't be using windows messages to exchange information - follow his advice and use some other form of inter process communications. Smile | :)

2+2=5 for very large amounts of 2
(always loved that one hehe!)

Re: Broadcasting custom windows message(Interprocess communication)

Mark Salsbery7-Aug-09 6:21

Mark Salsbery

7-Aug-09 6:21

callousfantom wrote:
a service written in Visual C++

A Windows service application? If so, services run in a different desktop
so you may want to use a more suitable IPC mechanism instead of window messages
which don't cross the desktop boundary.

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Broadcasting custom windows message(Interprocess communication)

callousfantom9-Aug-09 18:47

callousfantom

9-Aug-09 18:47

Are you trying to say that since the service (SYSTEM acct) is running under a different user context than the application, that the messages won't reach the application from the service? Because my application can communicate via messages with my service using its handle.I've already done that. This implies I can only communicate from the app. to the service and not the other way around. Or does it mean that I can only use handles to communicate one-to-one and broadcasting won't work? Neither of the two seem to make sense to me.

As for another way, I could use custom named events but I've already done one way via messages and I thought I could do the same thing in the other direction.

If there's something else you were trying to suggest then I'm sorry I don't think I quite understood you. Confused | :confused:

Re: Broadcasting custom windows message(Interprocess communication)

callousfantom9-Aug-09 23:14

callousfantom

9-Aug-09 23:14

Hi thanks for all the advice. I've managed to take care of it. I had to make the service interactive in order to make my application visible to it and I found no other way of making it visible due to the different user contexts. So you were right Blush | :O

How to communicate with Win CE device connected by usb

Deflinek7-Aug-09 1:23

Deflinek

7-Aug-09 1:23

Greetings.

I'm trying to communicate between desktop PC and Windows CE 5.0 device connected by usb (cradle).

I feel like I'm missing something obvious, because I can't find how to establish connection between them. What namespace to look? I just want simple communication: connect, exchange some data, disconnect. Sockets are more then enough, but what address should I access? The one assigned by usb connection on handheld is not accessible on desktop machine.

Communication should be initiated from desktop PC.
My handheld is running Windows CE 5.0 with .NET Compact Framework 2.0

Please point me to the right direction Smile | :)

--
"My software never has bugs. It just develops random features."

Re: How to communicate with Win CE device connected by usb

annathor10-Aug-09 2:27

annathor

10-Aug-09 2:27

Maybe take a look at the rapi.dll and see if it does what you need, you need to p/invoke the methodes.

Take a look here
And here

datagridview

akr_0456-Aug-09 23:08

akr_045

6-Aug-09 23:08

how to perform calculations in datagridview columns
(adding two columns and result in new column)

can any one suggest me any site

thanks in advance

Re: datagridview

Hypermommy7-Aug-09 2:25

Hypermommy

7-Aug-09 2:25

Some of the gurus on here will probably have a better idea for this but this is what I would try:

Dim myCol As New DataGridViewColumn   ' I think this is the type.  My code was an image column<br />
myCol.Name = "colname"<br />
dgvMyGrid.Columns.Insert(1, myCol)

Then you'll need to access the values of the numbers you need to add and the column where the result should go. I do most of my processing in my OnCellFormatting event. And in there, I access the values of the current row's items with something like this:

(sender.Rows(e.RowIndex).Cells(14).Value <br />

Of course, you'll need to know your column's number. And don't forget to account for the one you entered.

Hope this helps.

Denise "Hypermommy" Duggan

Re: datagridview

Jack Vanderhorst7-Aug-09 14:19

Jack Vanderhorst

7-Aug-09 14:19

If your DataGridView is bound to a DataTable then this may be what you're looking for:
http://msdn.microsoft.com/en-us/library/system.data.datacolumn.expression.aspx[^]

I love these columns, they're smokin' fast Smile | :)

Tabcontrol of Visual Studio 2005

J.K.Sharma6-Aug-09 22:52

J.K.Sharma

6-Aug-09 22:52

Hi
I have made a project and used

tabcontrol

of Visual Studio 2005. The problem is that when I run the project and bring the mouse arrow to the tab heading it start blinking/trembling.

Please, reply if anybody can.

Thanks in advance.

Re: Tabcontrol of Visual Studio 2005

Arindam Sinha7-Aug-09 3:04

Arindam Sinha

7-Aug-09 3:04

It does not give idea..Provide some details..some code snippet..otherwise none can understand..

Regards,
Arindam Sinha
MyBlog - http://arindamsinha.wordpress.com/
Please give your feedback on this answer.

Re: Tabcontrol of Visual Studio 2005

Luc Pattyn7-Aug-09 3:47

Luc Pattyn

7-Aug-09 3:47

seems like you have a lot of activity in some kind of hover event.

Smile | :)

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FTP Append in .net 1.1

Member 41816696-Aug-09 10:30

Member 4181669

6-Aug-09 10:30

Hi,
I want to append a file into a remote server file using FTP can you please suggest how i can do it .net 1.1

Thanks in Advance

Re: FTP Append in .net 1.1

N a v a n e e t h6-Aug-09 18:12

N a v a n e e t h

6-Aug-09 18:12

WebClient[^] class can work with FTP.

Navaneeth

How to use google | Ask smart questions

Re: FTP Append in .net 1.1

Member 41816697-Aug-09 11:52

Member 4181669

7-Aug-09 11:52

Webclient supports only upLoadFile and UpLoadData , But how can i use to append a file which is already existing in Server.
if you have any sample code to perform Append please provide me i will be great help

Thanks in Advance.

Re: FTP Append in .net 1.1

N a v a n e e t h7-Aug-09 18:27

N a v a n e e t h

7-Aug-09 18:27

Member 4181669 wrote:
But how can i use to append a file which is already existing in Server.

You need to read the existing file contents, do the appending from your application and upload the new file. FTP doesn't provide a way to append to a file.

Navaneeth

How to use google | Ask smart questions

Thread Sincronization Issue: Aborting thread with locked resources

Leonardo Muzzi6-Aug-09 7:40

Leonardo Muzzi

6-Aug-09 7:40

Hi. I've a multithreaded service application with many threads accessing a comom resource. I have a typical Readers/Writers environment, where many threads may read at the same time but only one can write to the resource, exclusively.

The thing is, whenever two threads (or more) asks for writing permission, I do not need to wait for the first thread to finish, I can just abort it (the first thread is no longer needed) and execute the second thread. Since writing is an expensive operation, it's desirable that I abort the first thread and execute the second.

So, here's my doubt: if I abort a thread that holds a lock, will it release the lock?

My simplified code looks like this:

private static System.Threading.Thread WritingThread =   
    System.Threading.Thread(MyClass.PerformWriting)

private void TryWrite()
{
   If (WritingThread.IsAlive)
      WritingThread.Abort();

   WritingThread.Start();
   
}

private void PerformWriting()
{
   MyReaderWriterLockSlim.EnterWriteLock();

   try{
      //writing operation - takes a long time
   }
   finally{
      MyReaderWriterLockSlim.ExitWriteLock();
   }
}

So here's the deal. I have a commom fixed writing thread for everybody, so I can test if the thread is already running, and if is, I can just abort it and initiate it again. This get the effect of aborting the first writing and executing the second. Whenever a thread needs to write to the resouce, it just calls the TryWrite function. The original calling thread doesn't need to wait the end of the operation, so it returns and finishes.

But, since "writing operation" takes a long time, it is more likely that the WritingThread will be aborted when it is writing, that is, when it holds the lock.

Is that code ok, or it will deadlock when the thread gets aborted in the middle of the writing?

Regards,

Leonardo Muzzi

Re: Thread Sincronization Issue: Aborting thread with locked resources

Luc Pattyn6-Aug-09 8:05

Luc Pattyn

6-Aug-09 8:05

Hi,

aborting a thread is a bad idea, as it (1) may not occur right away (e.g. when inside some I/O operations) and (2) will get kicked out in an unknown state, without getting a chance for cleaning up after itself.

so the recommendation is not to abort at all, rather to implement a cooperative thread exit scheme, where the thread regularly checks a flag to make sure it should continue its work or exit.

And as you would abort a thread to start a similar thread, there is no need to do any thread operation at all, just tell the thread to abandon its current job and start executing the new job.

Smile | :)

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Re: Thread Sincronization Issue: Aborting thread with locked resources

Leonardo Muzzi6-Aug-09 8:16

Leonardo Muzzi

6-Aug-09 8:16

Good !

I'll try implementing the "restart flag" inside the writing operation.

But, let's say I can not interfere in the writing code (I don't know if I can, not my implementation), so I can't change the writing operation to test a flag eventually. Any other ideas?

Thanks !

Regards,

Leonardo Muzzi

Re: Thread Sincronization Issue: Aborting thread with locked resources

Leonardo Muzzi6-Aug-09 8:32

Leonardo Muzzi

6-Aug-09 8:32

I'm thinking about implementing another thread that just sleeps for a while and checks for the flag, and abort the WritingThread if it finds the restart flag true. This new thread would hold the lock and therefore I can make sure it will release it.

Still, I'm aborting threads and creating new ones.

Is it good?

Regards,

Leonardo Muzzi

Re: Thread Sincronization Issue: Aborting thread with locked resources

Luc Pattyn6-Aug-09 8:38

Luc Pattyn

6-Aug-09 8:38

You don't need a thread to hold a lock; you can implement the thread stuff and the lock inside a class.

BTW: when you reply to yourself, you're the one getting the mail notification...

Smile | :)

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Re: Thread Sincronization Issue: Aborting thread with locked resources

Luc Pattyn6-Aug-09 8:35

Luc Pattyn

6-Aug-09 8:35

This[^] is the best I ever found about .NET threading.

Smile | :)

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