Can not terminate a thread when using SDK

[DavidLee]

I have code a program which will communicate between 2 process . At the server side , the code phase is as follows :


Static int quitFlag =1;
int main ()
{
int eThreadPoolHandle ;
HANDLE pipeHandle ;
int wThreadID ;
�.
CmtNewThreadPool (EGN_THREAD_NUM, &eThreadPoolHandle); //Create a thread pool
//Create a named pipe
pipeHandle=CreateNamedPipe(DATA_PIPE,PIPE_ACCESS_DUPLEX, PIPE_TYPE_BYTE|PIPE_READMODE_BYTE|PIPE_WAIT, AVAILABLE_PIPE_NUM,0, 0, INFINITE,NULL);
//Spawn a thread to monitor the connect from client side
CmtScheduleThreadPoolFunction (eThreadPoolHandle, WaitForConnectAsk, pipeHandle, &wThreadID);
�..
//When received the quit message , then do follows
CmtDiscardThreadPool (eThreadPoolHandle);

��
Ret
urn 0 ;
}


//The thread using to monitor the client�s call

int CVICALLBACK WaitForConnectAsk (void *functionData)
{
HANDLE pipeHandle ;

pipeHandle = functionData ;
while (quitFlag)
{
if(ConnectNamedPipe(pipeHandle,NULL))// Once there is a connect call , then execute the task
{
/* doing something */
���.
DisconnectNamedPipe(pipeHandle);
}
Sleep(300);
}

CloseHandle(pipeHandle);
return 0;
}

The problem is when execute the sentence "ConnectNamedPipe(pipeHandle,NULL)" , it will always wait for the client call , any belows sentence will not be executed . So when press the Quit button on the panel , I need finish the thread first but it seems not has any method to perform the task . Anyone can advise me how to terminate the thread ? Thanks.

David

[JuanCarlos]

David,

The trick here is not in the ConnectNamedPipe;to be able to execute the ConnectNamedPipe wihtout blocking you execution you must specify this when you create the pipe.

When you call CreateNamedPipe you are specifying in the dwPipeMode parameter PIPE_WAIT; this causes the call to ConnectNamedPipe to hang until there is a connection thus not allowing you to terminate your application prperly.

Change that flag to PIPE_NOWAIT and you while loop should be running constantly, you may want to add a small delay there too.

I hope this helps.

Juan Carlos
N.I.

[DavidLee]

Hello Juan,

yes ,you are right. but in this situation , the ConnectNamedPipe() always return FALSE, because my condition is this : if(ConnectNamedPipe(...)){ MessageBox(...);...}. So when the client using CreateFile(...) to construct a connect , I can not find the dialog window popup by the MesageBox(). I am not sure if it is due to the competion .

David

[Jeremy_L]

Hi David,

The messagebox seems to only open if there is a valid connection to the pipe, as per your code. So, that may be why you are not seeing a messagebox appear. You would probably have to do some time of polling loop to run ConnectNamedPipe, and until there is a valid connection or the user presses the quit button will you exit that loop and finish out the function.

Jeremy L.
National Instruments

[DavidLee]

Hi Jeremy,

I am not clear what you said , could you show a code phase ? thanks.

David Lee

[Jeremy_L]

I meant something like this:

while (quitFlag)
{
int status;
do{
status = ConnectNamedPipe(pipeHandle,NULL));
} while (status == NOT_CONNECTED || quitFlag);
if (status == CONNECTED)
{
/* do your work */
}
}

Basically, add another loop to wait for a connection or a stop sign. That way, regardless of if you get the connection or not, if you press 'Stop', it'll quit out of your loops.

Jeremy L.
National Instruments

[DavidLee]

Thanks Jeremy, I'll try it .

David