nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping_nw socket

更新Xcode8.2以后 做个项目，发现控制台有如下的打印，项目可以正常运行。然而 出现了这样....fail，开始以为是与网络有关系，有类似socket的字样，然后去stackflower查阅资料，得知还是如8.1是多余的打印信息。 

Xcode->EditScheme ->Run -> Arguments ->Environment Variables ->添加 Name（OS_ACTIVITY_MODE）:Value(disable)即可去除这条打印信息。

[] nw_socket_set_common_sockopts setsockopt SO_NOAPNFALLBK failed: [42] Protocol not available, dumping backtrace:

        [x86_64] libnetcore-856.30.16

    0   libsystem_network.dylib             0x000000010caec666 __nw_create_backtrace_string + 123

    1   libnetwork.dylib                    0x000000010d8da006 nw_socket_add_input_handler + 3164

    2   libnetwork.dylib                    0x000000010d8b7555 nw_endpoint_flow_attach_protocols + 3768

    3   libnetwork.dylib                    0x000000010d8b6572 nw_endpoint_flow_setup_socket + 563

    4   libnetwork.dylib                    0x000000010d8b5298 -[NWConcrete_nw_endpoint_flow startWithHandler:] + 2612

    5   libnetwork.dylib                    0x000000010d8d0ae1 nw_endpoint_handler_path_change + 1261

    6   libnetwork.dylib                    0x000000010d8d0510 nw_endpoint_handler_start + 570

    7   libdispatch.dylib                   0x000000010c869978 _dispatch_call_block_and_release + 12

    8   libdispatch.dylib                   0x000000010c8930cd _dispatch_client_callout + 8

    9   libdispatch.dylib                   0x000000010c870e17 _dispatch_queue_serial_drain + 236

    10  libdispatch.dylib                   0x000000010c871b4b _dispatch_queue_invoke + 1073

    11  libdispatch.dylib                   0x000000010c874385 _dispatch_root_queue_drain + 720

    12  libdispatch.dylib                   0x000000010c874059 _dispatch_worker_thread3 + 123

    13  libsystem_pthread.dylib             0x000000010cc3c4de _pthread_wqthread + 1129

    14  libsystem_pthread.dylib             0x000000010cc3a341 start_wqthread + 13