支持苹果IPV6 ONLY 的socket 修改方法

首先别错误理解以为app 必须支持 ipv6 的服务端， 只需要支持 ipv6的客户端需要访问 ipv4 的服务端。

目前需要经过  NAT64 转换就能达到目的，客户端只需要支持该转换就能实现， 在OS X的系统上是的wifi 共享有支持 NAT64转换，提供了这个功能就方便了我们可以使用手机链接 OS X上的热点模拟这个测试环境。

我们代码上所需要完成​的事情：

1.客户端需要链接的ip地址(ipv4) 通过转换。

 getaddrinfo​ //方法可以转换为 ipv6 的地址。

 ​struct addrinfo hints, *res, *res0;

 memset(&hints, , sizeof(hints));

 hints.ai_family = PF_UNSPEC;

 hints.ai_socktype = SOCK_STREAM;

 #if (PLATFORM == PLATFORM_WIN32)

 hints.ai_flags = AI_PASSIVE;

 #else

 hints.ai_flags = AI_DEFAULT;
18 #endif

 int error = getaddrinfo(pServerIP, "http", &hints, &res0);

2.经过转换后我们可以判断 ai_family 兼容 非NAT64 转换的网络环境与 NAT64转换的网络环境 下进行 socket的链接：

 struct sockaddr_in addr_in;

 struct sockaddr_in6 addr_in6;

 int connect_ret;

 for (res = res0; res; res = res->ai_next) {

      connect_ret = -;

       tempSocket = socket(res->ai_family, res->ai_socktype, res->ai_protocol);

      if (tempSocket < ) {

              continue;

        }

       if(AF_INET == res->ai_family){

            addr_in = *((struct sockaddr_in *)res->ai_addr);

            addr_in.sin_port = htons(ServerPort);

            connect_ret = connect(tempSocket, (struct sockaddr *)&addr_in, res-      >ai_addrlen);

         }else if(AF_INET6 == res->ai_family){

                 addr_in6  = *((struct sockaddr_in6 *)res->ai_addr);

                 addr_in6.sin6_port = htons(ServerPort);

                 connect_ret = connect(tempSocket, (struct sockaddr *)&addr_in6, res->ai_addrlen);

         }

        if (connect_ret < ) {

             cause = "connect";

 #if (PLATFORM == PLATFORM_WIN32)

             closesocket(tempSocket);

 #else

             close(tempSocket);

 #endif

             tempSocket = -;

             continue;

       }

       break; 

 }

OK，这样就支持 ipv6 对 ipv4 的网络 而且兼容 普通 ipv4 对 ipv4 的网络。​

上面是没有考虑链接时候客户端会进入卡死状态直到链接成功， 因为加上去代码会复杂点，为了好看就没有加上， 真实项目中需要改为非阻塞模式， 通过select 来判断是否connect成功。

下面是加上非阻塞模式：

     int tempSocket = -;
     struct addrinfo hints, *res, *res0;
     int error;
     const char *cause = NULL; 

     memset(&hints, , sizeof(hints));
     hints.ai_family = PF_UNSPEC;
     hints.ai_socktype = SOCK_STREAM;

     error = getaddrinfo(pServerIP, NULL, &hints, &res0);
     if (error) {
         CCLOG("getaddrinfo error:%d", error);
         return false;
     }

     struct sockaddr_in addr_in;
     struct sockaddr_in6 addr_in6;
     for (res = res0; res; res = res->ai_next) {
         tempSocket = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
         if (tempSocket < ) {
             cause = "socket";
             continue;
         }

 #if (CC_TARGET_PLATFORM == CC_PLATFORM_WIN32)
         // 设定 非阻塞
         unsigned long tmepOption = ;  //0：阻塞
         ioctlsocket(tempSocket, FIONBIO, &tmepOption);
 #else
         // 设定 非阻塞
         int flag = fcntl(tempSocket, F_GETFL, );
         fcntl(tempSocket, F_SETFL, flag | O_NONBLOCK);
 #endif

         if(AF_INET == res->ai_family){
             addr_in = *((struct sockaddr_in *)res->ai_addr);
             addr_in.sin_port = htons(ServerPort);
             connect(tempSocket, (struct sockaddr *)&addr_in, res->ai_addrlen);
         }else if(AF_INET6 == res->ai_family){
             addr_in6 = *((struct sockaddr_in6 *)res->ai_addr);
             addr_in6.sin6_port = htons(ServerPort);
             connect(tempSocket, (struct sockaddr *)&addr_in6, res->ai_addrlen);
         }

         fd_set fset;
         FD_ZERO(&fset);
         FD_SET(tempSocket, &fset);

         timeval timeout;
         timeout.tv_sec  = ;  // 1.5秒超时, 上层逻辑会尝试3次 >> 1.5 * 3
         timeout.tv_usec = ;
 #if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)
         socklen_t len = sizeof(error);
 #else
         int len = sizeof(error);
 #endif
         if( select(tempSocket+, NULL, &fset, NULL, &timeout) > )
         {
             if (FD_ISSET(tempSocket, &fset))
             {
                 getsockopt(tempSocket, SOL_SOCKET, SO_ERROR, (char *)&error, &len);
                 if(error == ){
                     break;
                 }
             }
         }

 #if (CC_TARGET_PLATFORM == CC_PLATFORM_WIN32)
         closesocket(tempSocket);
 #else
         close(tempSocket);
 #endif
         tempSocket = -; 

     }

     if (tempSocket < ) {
         CCLOG("connect server error:%d", tempSocket);
         goto RETURN_FALSE;
     }

     if(false){
 RETURN_FALSE:
         freeaddrinfo(res0);
         return false;
     }