error "Passing address of non-local object to __autoreleasing parameter for write-back"

I'm converting my socket client to ARC: - (id)initWithHostname:(NSString *)hostname AndPort:(NSInteger)port { if((self = [super init])) { oBuffer = [[NSMutableData alloc] init]; iBuffer = [[NSMutableData alloc] init]; iStream = [[NSInputStream alloc] init]; oStream = [[NSOutputStream alloc] init]; [NSStream getStreamsToHost:[NSHost hostWithName:hostname] port:port inputStream:&iStream outputStream