DNSServiceNATPortMappingCreate始终返回错误代码-65540

Question

我正在做一个ios应用程序，它启动一个服务器并监听传入的连接，运行应用程序的设备可能在路由器后面，所以我需要建立一个端口转发。 我正在尝试使用DNSServiceNATPortMappingCreate创建一个端口，但它总是返回错误代码-65540

DNSServiceRef *sdRef = NULL ;
void ( *DNSServiceNATPortMappingReply) (DNSServiceRef sdRef,
                                        DNSServiceFlags flags,
                                        uint32_t interfaceIndex,
                                        DNSServiceErrorType errorCode,
                                        uint32_t externalAddress,
                                        DNSServiceProtocol protocol,
                                        uint16_t internalPort,
                                        uint16_t externalPort,
                                        uint32_t ttl,
                                        void *context );

DNSServiceNATPortMappingReply = &DNSServiceNATPortMappingCreate_callback ;

DNSServiceErrorType error = DNSServiceNATPortMappingCreate(sdRef,
                                                           0,
                                                           0,
                                                           kDNSServiceProtocol_TCP,
                                                           htons(2000),
                                                           htons(5000),
                                                           0,
                                                          DNSServiceNATPortMappingReply,
                                                           NULL
) ;

这是回调

void DNSServiceNATPortMappingCreate_callback(
                                         DNSServiceRef sdRef,
                                         DNSServiceFlags flags,
                                         uint32_t interfaceIndex,
                                         DNSServiceErrorType errorCode,
                                         uint32_t externalAddress, 
                                         DNSServiceProtocol protocol,
                                         uint16_t internalPort, 
                                         uint16_t externalPort, 
                                         uint32_t ttl, 
                                         void *context )
{
    printf("in callback\n") ;
}

Answer 1

根据DNSServiceDiscovery的文档，错误代码-65540表示kDNSServiceErr_BadParam。

DNSServiceNATPortMappingCreate的文档建议您必须为作为第一个参数传递的DNSServiceRef分配存储空间。即你需要改变

DNSServiceRef *sdRef = NULL ;
DNSServiceErrorType error = DNSServiceNATPortMappingCreate(sdRef, ...

到

DNSServiceRef sdRef;
DNSServiceErrorType error = DNSServiceNATPortMappingCreate(&sdRef, ...