A function multi-threaded by:

```
[NSThread detachNewThreadSelector:@selecter(download:) toTarget:..... withObject:....];

```

Called a callback function inside. Before multi-threading, the callback mechanism worked fine, 
but now the callback function is never called.

I have checked that the threaded-function works.

Below is the code, thank you very much.

```
+(void) download:(id) param{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];  

    while(true){
        NSLog(@"Thread going ");
        NSArray* ary = [Data_Center sharedData_Center]->data;

        for(int i = 0; i < [ary count]; i++) {
            NSLog(@"code = %@", code);
            ..........            
            NSURL* url1 = [NSURL URLWithString:str_code];

            [str_code length];

            CFStreamClientContext dataStreamContext = {0, self, NULL, NULL, NULL};

            CFHTTPMessageRef message = CFHTTPMessageCreateRequest(kCFAllocatorDefault, CFSTR("GET"), (CFURLRef)url1, kCFHTTPVersion1_1);
            CFHTTPMessageSetBody(message, (CFDataRef)(CFSTR("")));

            CFReadStreamRef readStream = CFReadStreamCreateForHTTPRequest(kCFAllocatorDefault, message);
            CFOptionFlags events = kCFStreamEventHasBytesAvailable | kCFStreamEventErrorOccurred | kCFStreamEventEndEncountered;

            // print "client = 1" here                    
            //NSLog(@"client = %d" , CFReadStreamSetClient(readStream, events, readStreamEventCallBack, & dataStreamContext));

            if(CFReadStreamSetClient(readStream, events, readStreamEventCallBack, & dataStreamContext)) {
                CFReadStreamScheduleWithRunLoop(readStream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);
            }

            CFReadStreamOpen(readStream);
        }

        [NSThread sleepForTimeInterval:10];
    }
    [pool release];

}

```