Socket ==> recv ==> returns -1 ?!?!?!?

[aryaxt]

Sorry that my question is not directly related to iphone.
Ok I finally got the socket on iphone to connect to my server and send messages , but it can't receilve any messages. The recv function returns -1
What does -1 mean?

- (void) Receive
{
	NSThread *myThread=[[NSThread alloc]initWithTarget:self 
											selector:@selector(ReceiveOperation) 
											  object:nil]; 
	[myThread start]; 
	[myThread release];

}

- (void) ReceiveOperation
{
	NSAutoreleasePool *pool=[[NSAutoreleasePool alloc]init]; 
	char buffer[512];
	int bytesReceived = recv(_socket, buffer, sizeof(buffer), MSG_OOB);
	if (bytesReceived > 0)
	{
			printf("%s\n", [@"recv bytes" UTF8String]);
	}
	//buffer= NULL;
	NSThread *myThread=[[NSThread alloc]initWithTarget:self 
											  selector:@selector(ReceiveOperation) 
												object:nil]; 
	[myThread start]; 
	[myThread release];
	[pool release];
}

Does my code look fine?
Thanks You