Example: IPv4 or IPv6 client

This sample program can be used with the server application that accepts requests from either IPv4 or IPv6 clients.

Note: By using the examples, you agree to the terms of the Code license and disclaimer information.

/**************************************************************************//* This is an IPv4 or IPv6 client.                                        *//**************************************************************************//**************************************************************************//* Header files needed for this sample program                            *//**************************************************************************/#include <stdio.h>#include <string.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <netdb.h>/**************************************************************************//* Constants used by this program                                         *//**************************************************************************/#define BUFFER_LENGTH    250#define FALSE              0#define SERVER_NAME     "ServerHostName"/* Pass in 1 parameter which is either the *//* address or host name of the server, or  *//* set the server name in the #define      *//* SERVER_NAME.                            */void main(int argc, char *argv[]){   /***********************************************************************/   /* Variable and structure definitions.                                 */   /***********************************************************************/   int    sd=-1, rc, bytesReceived=0;   char   buffer[BUFFER_LENGTH];   char   server[NETDB_MAX_HOST_NAME_LENGTH];   char   servport[] = "3005";   struct in6_addr serveraddr;   struct addrinfo hints, *res=NULL;   /***********************************************************************/   /* A do/while(FALSE) loop is used to make error cleanup easier.  The   */   /* close() of the socket descriptor is only done once at the very end  */   /* of the program along with the free of the list of addresses.        */ /***********************************************************************/   do   {      /********************************************************************/      /* If an argument was passed in, use this as the server, otherwise  */      /* use the #define that is located at the top of this program.      */      /********************************************************************/      if (argc > 1)         strcpy(server, argv[1]);      else         strcpy(server, SERVER_NAME);      memset(&hints, 0x00, sizeof(hints));      hints.ai_flags    = AI_NUMERICSERV;      hints.ai_family   = AF_UNSPEC;      hints.ai_socktype = SOCK_STREAM;      /********************************************************************/      /* Check if we were provided the address of the server using        */      /* inet_pton() to convert the text form of the address to binary    */      /* form. If it is numeric then we want to prevent getaddrinfo()     */      /* from doing any name resolution.                                  */      /********************************************************************/      rc = inet_pton(AF_INET, server, &serveraddr);      if (rc == 1)    /* valid IPv4 text address? */      {         hints.ai_family = AF_INET;         hints.ai_flags |= AI_NUMERICHOST;      }      else      {         rc = inet_pton(AF_INET6, server, &serveraddr);         if (rc == 1) /* valid IPv6 text address? */         {            hints.ai_family = AF_INET6;            hints.ai_flags |= AI_NUMERICHOST;         }      }      /********************************************************************/      /* Get the address information for the server using getaddrinfo().  */      /********************************************************************/      rc = getaddrinfo(server, servport, &hints, &res);      if (rc != 0)      {         printf("Host not found --> %s\n", gai_strerror(rc));         if (rc == EAI_SYSTEM)            perror("getaddrinfo() failed");         break;      }      /********************************************************************/      /* The socket() function returns a socket descriptor, which represents   */      /* an endpoint.  The statement also identifies the address family,  */      /* socket type, and protocol using the information returned from    */      /* getaddrinfo().                                                   */      /********************************************************************/      sd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);      if (sd < 0)      {         perror("socket() failed");         break;      }      /********************************************************************/      /* Use the connect() function to establish a connection to the      */      /* server.                                                          */      /********************************************************************/      rc = connect(sd, res->ai_addr, res->ai_addrlen);      if (rc < 0)      {         /*****************************************************************/         /* Note: the res is a linked list of addresses found for server. */         /* If the connect() fails to the first one, subsequent addresses */         /* (if any) in the list can be tried if required.               */         /*****************************************************************/         perror("connect() failed");         break;      }      /********************************************************************/      /* Send 250 bytes of a's to the server                              */      /********************************************************************/      memset(buffer, 'a', sizeof(buffer));      rc = send(sd, buffer, sizeof(buffer), 0);      if (rc < 0)      {         perror("send() failed");         break;      }      /********************************************************************/      /* In this example we know that the server is going to respond with */      /* the same 250 bytes that we just sent.  Since we know that 250    */      /* bytes are going to be sent back to us, we can use the          */      /* SO_RCVLOWAT socket option and then issue a single recv() and     */      /* retrieve all of the data.                                        */      /*                                                                  */      /* The use of SO_RCVLOWAT is already illustrated in the server      */      /* side of this example, so we will do something different here.    */      /* The 250 bytes of the data may arrive in separate packets,        */      /* therefore we will issue recv() over and over again until all     */      /* 250 bytes have arrived.                                          */      /********************************************************************/      while (bytesReceived < BUFFER_LENGTH)      {         rc = recv(sd, & buffer[bytesReceived],                   BUFFER_LENGTH - bytesReceived, 0);         if (rc < 0)         {            perror("recv() failed");            break;         }         else if (rc == 0)         {            printf("The server closed the connection\n");            break;         }         /*****************************************************************/         /* Increment the number of bytes that have been received so far  */         /*****************************************************************/         bytesReceived += rc;      }   } while (FALSE);   /***********************************************************************/   /* Close down any open socket descriptors                              */   /***********************************************************************/   if (sd != -1)      close(sd);   /***********************************************************************/   /* Free any results returned from getaddrinfo                          */   /***********************************************************************/   if (res != NULL)      freeaddrinfo(res);
}
https://www.ibm.com/support/knowledgecenter/ssw_i5_54/rzab6/xip6client.htm
再转一篇windows上的使用ipv6的文章
https://msdn.microsoft.com/en-us/library/windows/desktop/ms738639(v=vs.85).aspx