NSFileHandle readInBackgroundAndNotify example ios

readInBackgroundAndNotify

Reads from the file or communications channel in the background and posts a notification when finished.

- (void)readInBackgroundAndNotify

Discussion

This method performs an asynchronous availableData operation on a file or communications channel and posts anNSFileHandleReadCompletionNotification notification on the current thread when that operation is complete. You must call this method from a thread that has an active run loop.[NSFileHandle readInBackgroundAndNotify]

The length of the data is limited to the buffer size of the underlying operating system. The notification includes auserInfo dictionary that contains the data read; access this object using the NSFileHandleNotificationDataItem key.[NSFileHandle readInBackgroundAndNotify]

Any object interested in receiving this data asynchronously must add itself as an observer ofNSFileHandleReadCompletionNotification. In communication via stream-type sockets, the receiver is often the object returned in the userInfo dictionary of NSFileHandleConnectionAcceptedNotification.

Note that this method does not cause a continuous stream of notifications to be sent. If you wish to keep getting notified, you’ll also need to call readInBackgroundAndNotify in your observer method.

Example of [NSFileHandle readInBackgroundAndNotify]

-(void)createSocket 

{

    // create socket and wait for events to come in

    NSSocketPort* serverSock = [[NSSocketPort alloc] initWithTCPPort: 1234];

    socketHandle = [[NSFileHandle alloc] initWithFileDescriptor: [serverSock socket]

                                                 closeOnDealloc: NO];

    [[NSNotificationCenter defaultCenter] addObserver: self selector: @selector(newConnection:) 

                                                 name: NSFileHandleConnectionAcceptedNotification

                                               object: socketHandle];

    [socketHandle acceptConnectionInBackgroundAndNotify];

}

- (void)newConnection:(NSNotification*)notification

{

    NSLog(@"connection accepted");

    NSDictionary* userInfo = [notification userInfo];

    NSFileHandle* remoteFileHandle = [userInfo objectForKey:

                                      NSFileHandleNotificationFileHandleItem];

    if([[userInfo allKeys] containsObject:@"NSFileHandleError"]){

        NSNumber* errorNo = [userInfo objectForKey:@"NSFileHandleError"];

        if( errorNo ) {

            NSLog(@"NSFileHandle Error: %@", errorNo);

            return;

        }

    }

    [socketHandle acceptConnectionInBackgroundAndNotify];

    [[NSNotificationCenter defaultCenter] addObserver:self 

       selector: @selector(processSocketData:)

           name: NSFileHandleReadCompletionNotification

         object: remoteFileHandle];

    // Send a message to the client, acknowledging that the connection was accepted

    [remoteFileHandle writeData: [@"OK" dataUsingEncoding: NSASCIIStringEncoding]];

    [remoteFileHandle readInBackgroundAndNotify];

}