Running NSStream in background Thread - objective-c

Question

I'm currently trying to run my whole network stuff in a background thread, as it currently blocks the main thread, when the server is not reachable (i.e.).
I'm currently creating the network connection through the following code. Is there a simple way to run this in a new background thread?
An how can I throw back the received message to the main thread? An how can I send messages through the background thread?
CFReadStreamRef readStream;
CFWriteStreamRef writeStream;
CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)ipAdress, port, &readStream, &writeStream);
inputStream = (__bridge NSInputStream *)readStream;
outputStream = (__bridge NSOutputStream *)writeStream;
[inputStream setDelegate:self];
[outputStream setDelegate:self];
[inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
[inputStream open];
[outputStream open];

Answer 1

here is a tutorial that does exactly what you're talking about. although it focuses more on audio streaming, but the principles are exactly the same (ie in terms of spawning a worker thread, having it talk with the parent thread etc etc).
the idea is simple.. you create a new thread and have it handle the streaming work, and then you schedule the stream reader with the run loop that belongs to the thread you just created. The stream will have callbacks that will be fired when ceratain events happen (ie you get some data, the connect times out etc).. in the callback methods you can alert or communicate with the mainthread (which is the thread that handles the UI).
Here is some code to point you in the right direction, but if you download the code from the above tutorial and follow through.. you'll get it:
// create a new thread
internalThread =
[[NSThread alloc]
initWithTarget:self
selector:#selector(startInternal)
object:nil];
[internalThread start];
// creating a stream inside the 'startInternal' thread*
stream = CFReadStreamCreateForHTTPRequest(NULL, message);
// open stream
CFReadStreamOpen(stream)
// set callback functions
// ie say: if there are bites available in the stream, fire a callback etc
CFStreamClientContext context = {0, self, NULL, NULL, NULL};
CFReadStreamSetClient(
stream,
kCFStreamEventHasBytesAvailable | kCFStreamEventErrorOccurred | kCFStreamEventEndEncountered,
ASReadStreamCallBack,
&context);
// schedule stream in current thread runloop, so that we DON'T block the mainthread
CFReadStreamScheduleWithRunLoop(stream, CFRunLoopGetCurrent(), kCFRunLoopCommonModes);
// create the callback function to handle reading from stream
// NOTE: see where else in the code this function is named (ie CFReadStreamSetClient)
static void ASReadStreamCallBack
(
CFReadStreamRef aStream,
CFStreamEventType eventType,
void* inClientInfo
)
{
//handle events you registered above
// ie
if (eventType == kCFStreamEventHasBytesAvailable) {
// handle network data here..
..
// if something goes wrong, create an alert and run it through the main thread:
UIAlertView *alert = [
[[UIAlertView alloc]
initWithTitle:title
message:message
delegate:self
cancelButtonTitle:NSLocalizedString(#"OK", #"")
otherButtonTitles: nil]
autorelease];
[alert
performSelector:#selector(show)
onThread:[NSThread mainThread]
withObject:nil
waitUntilDone:NO];
}
}