在xcode8下运行iphone6s的模拟器，在日志里看到了下面的信息如下：
[] nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping backtrace:
[x86_64] libnetcore-856.1.8
0 libsystem_network.dylib 0x000000010badf80e __nw_create_backtrace_string + 123
1 libnetwork.dylib 0x000000010c6e4194 nw_socket_add_input_handler + 3002
2 libnetwork.dylib 0x000000010c6c1db8 nw_endpoint_flow_attach_protocols + 3768
3 libnetwork.dylib 0x000000010c6c0dd5 nw_endpoint_flow_setup_socket + 563
4 libnetwork.dylib 0x000000010c6bfb34 -[NWConcrete_nw_endpoint_flow startWithHandler:] + 2612
5 libnetwork.dylib 0x000000010c6dad11 nw_endpoint_handler_path_change + 1261
6 libnetwork.dylib 0x000000010c6da740 nw_endpoint_handler_start + 570
7 libnetwork.dylib 0x000000010c6f2003 nw_endpoint_resolver_start_next_child + 2240
8 libdispatch.dylib 0x000000
解决方法就是
在xcode,进入菜单product-scheme-edit scheme 添加环境变量 OS_ACTIVITY_MODE 为 disable 即可，如下图
