写一个 socket绑定iPv4和ipv6 源码

以下是一个简单的示例代码，用于在同一个 socket 上绑定 IPv4 和 IPv6 地址：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>

int main(int argc, char *argv[]) {
    int sockfd, status;
    struct addrinfo hints, *res, *p;
    char ipstr[INET6_ADDRSTRLEN];

    memset(&hints, , sizeof hints);
    hints.ai_family = AF_UNSPEC; // IPv4 or IPv6
    hints.ai_socktype = SOCK_STREAM; // TCP stream sockets

    if ((status = getaddrinfo("localhost", "808", &hints, &res)) != ) {
        fprintf(stderr, "getaddrinfo error: %s\n", gai_strerror(status));
        exit(1);
    }

    // loop through all the results and bind to the first we can
    for (p = res; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
            perror("socket");
            continue;
        }

        // set socket options to allow both IPv4 and IPv6
        int yes = 1;
        if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY, &yes, sizeof(yes)) == -1) {
            perror("setsockopt");
            exit(1);
        }

        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("bind");
            continue;
        }

        break;
    }

    if (p == NULL) {
        fprintf(stderr, "failed to bind socket\n");
        exit(1);
    }

    // convert the IP address to a string and print it
    void *addr;
    if (p->ai_family == AF_INET) {
        struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
        addr = &(ipv4->sin_addr);
    } else {
        struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
        addr = &(ipv6->sin6_addr);
    }
    inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
    printf("bound to %s\n", ipstr);

    freeaddrinfo(res); // free the linked list

    return ;
}

这个示例代码使用了 `getaddrinfo()` 函数来获取一个或多个与指定主机名和服务名匹配的地址信息。然后，它循环遍历这些地址信息，尝试在每个地址上绑定一个 socket。在绑定之前，它还设置了一个 socket 选项，以允许同时支持 IPv4 和 IPv6。最后，它将绑定的 IP 地址转换为字符串，并打印出来。