程序启动,自以为的,在loop中循环,在loop中加入socket监听端口,还需要loop一直循环么?
答案自然不知道,但事实问题,在这种队列中监听.
导致其他线程出问题了.
1.创建随机队列方法不了解.
2.监听端口的机制学习.

下面是一个错误的示范,时刻留意这个bug.

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    CFSocketContext ctx = { 0, self, NULL, NULL, NULL };
    recvSocket_ = CFSocketCreate(kCFAllocatorDefault,
                                 PF_INET,
                                 SOCK_DGRAM,
                                 IPPROTO_UDP,
                                 kCFSocketDataCallBack,
                                 (CFSocketCallBack)DiscoverReceiveCallback,
                                 &ctx);
    
    if (recvSocket_ == NULL) {
        LOG(@"[DSCV] Cannot create listening socket. %d", errno);
        return ;
    }
    
    int flag = 1;
    setsockopt(CFSocketGetNative(recvSocket_), SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag));
    
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_len = sizeof(addr);
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = INADDR_ANY;
    
    NSData *addrData = [NSData dataWithBytes:&addr length:sizeof(addr)];
    if (CFSocketSetAddress(recvSocket_, (CFDataRef)addrData)) {
        CFSocketInvalidate(recvSocket_);
        CFRelease(recvSocket_);
        recvSocket_ = NULL;
        LOG(@"[DSCV] Cannot set address to socket.");
        return ;
    }
    LOG(@"recvSocket_------>%@",recvSocket_);
    CFRunLoopSourceRef source = CFSocketCreateRunLoopSource(kCFAllocatorDefault, recvSocket_, 0);
    CFRunLoopAddSource(CFRunLoopGetCurrent(), source, kCFRunLoopCommonModes);
    CFRelease(source);
    
   CFRunLoopRun();  });