IPv4客户端和IPv6服务器端通信的c语言代码demo

以下是一个简单的示例代码，展示了如何使用C语言在IPv4客户端和IPv6服务器端之间进行通信：

IPv4客户端代码：

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

#define PORT "8080"

int main(int argc, char *argv[]) {
    int sockfd;
    struct addrinfo hints, *servinfo, *p;
    int rv;
    char s[INET6_ADDRSTRLEN];
    char buf[1024];

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    if ((rv = getaddrinfo("localhost", PORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

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

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

        break; // if we get here, we must have connected successfully
    }

    if (p == NULL) {
        fprintf(stderr, "client: failed to connect\n");
        return 2;
    }

    inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr),
            s, sizeof s);
    printf("client: connecting to %s\n", s);

    freeaddrinfo(servinfo); // all done with this structure

    while (1) {
        printf("Enter message to send: ");
        fgets(buf, sizeof(buf), stdin);

        if (send(sockfd, buf, strlen(buf), 0) == -1) {
            perror("send");
            exit(1);
        }

        printf("Waiting for server response...\n");
        int numbytes;
        if ((numbytes = recv(sockfd, buf, sizeof(buf), 0)) == -1) {
            perror("recv");
            exit(1);
        }

        buf[numbytes] = '\0';
        printf("Server response: %s\n", buf);
    }

    close(sockfd);

    return 0;
}

IPv6服务器端代码：

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

#define PORT "8080"

void *get_in_addr(struct sockaddr *sa) {
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void) {
    int sockfd, new_fd; // listen on sock_fd, new connection on new_fd
    struct addrinfo hints, *servinfo, *p;
    struct sockaddr_storage their_addr; // connector's address information
    socklen_t sin_size;
    int yes = 1;
    char s[INET6_ADDRSTRLEN];
    char buf[1024];
    int rv;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE; // use my IP

    if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

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

        if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
                sizeof(int)) == -1) {
            perror("setsockopt");
            exit(1);
        }

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

        break;
    }

    if (p == NULL) {
        fprintf(stderr, "server: failed to bind\n");
        return 2;
    }

    freeaddrinfo(servinfo); // all done with this structure

    if (listen(sockfd, 10) == -1) {
        perror("listen");
        exit(1);
    }

    printf("server: waiting for connections...\n");

    while (1) { // main accept() loop
        sin_size = sizeof their_addr;
        new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
        if (new_fd == -1) {
            perror("accept");
            continue;
        }

        inet_ntop(their_addr.ss_family,
                get_in_addr((struct sockaddr *)&their_addr),
                s, sizeof s);
        printf("server: got connection from %s\n", s);

        while (1) {
            int numbytes;
            if ((numbytes = recv(new_fd, buf, sizeof(buf), 0)) == -1) {
                perror("recv");
                exit(1);
            }

            if (numbytes == 0) {
                printf("Connection closed\n");
                break;
            }

            buf[numbytes] = '\0';
            printf("Client message: %s", buf);

            if (send(new_fd, buf, numbytes, 0) == -1) {
                perror("send");
                exit(1);
            }
        }

        close(new_fd); // parent doesn't need this
    }

    return 0;
}

注意：在IPv6服务器端代码中，我们使用了一个名为`get_in_addr()`的函数，它将IPv4和IPv6地址转换为通用的地址格式。在IPv4情况下，它返回`sin_addr`字段，而在IPv6情况下，它返回`sin6_addr`字段。