NSNetService问题

setTXTRecordData:

-(void)netServiceBrowser:(NSNetServiceBrowser *)aNetServiceBrowser didFindService:(NSNetService *)aNetService moreComing:(BOOL)moreComing
{
    [aNetService retain];

    [aNetService setDelegate:self];
    [aNetService startMonitoring];

    [aNetService performSelectorOnMainThread:@selector(resolve) withObject:nil waitUntilDone:YES];
[_serviceInstances addObject:aNetService];
}

NSNetService*service = [_serviceInstances objectAtIndex:[servicesTable selectedRow]];

[service setDelegate:self];

NSDictionary*txtRecordDataDictionary = [NSDictionary dictionaryWithObject:@\"2\" forKey:@\"Version\"];

if (service)
{
    BOOL success = [service setTXTRecordData:[NSNetService dataFromTXTRecordDictionary:txtRecordDataDictionary]];   

    if (!success)
    {
        NSRunCriticalAlertPanel(@\"Sync Error\", @\"Failed to contact Client. Please restart Carbon on your iPad and try again.\", @\"OK\", nil, nil);
    }

    NSLog(@\"Service: %@\",service);
}

NSNetService*service = [[NSNetService alloc] initWithDomain:@\"local.\" type:@\"_test._tcp.\" name:[[UIDevice currentDevice] name] port:28];
[service setDelegate:self];
[service setTXTRecordData:nil];
[service publish];

[service startMonitoring];


- (void)netService:(NSNetService *)sender didUpdateTXTRecordData:(NSData *)data
{
    NSLog(@\"Got Data! of %@\",sender);

    NSPropertyListFormat format;
    NSDictionary*dict = [NSPropertyListSerialization propertyListFromData:data mutabilityOption:NSPropertyListImmutable format:&format errorDescription:nil];


    UIAlertView *myAlert = [[UIAlertView alloc]
                            initWithTitle:[sender name] message:[dict objectForKey:@\"Version\"]
                            delegate:self 
                            cancelButtonTitle:nil
                            otherButtonTitles:@\"OK\", nil];
    [myAlert show];  
    [myAlert release];
}