// b->服务端
#include <stdio.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>

int main(int argc, char const *argv[])
{
    int sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock_fd < 0)
    {
        perror("socket");
        return -1;
    }

    struct sockaddr_in addr;
    bzero(&addr, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8000);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);

    if (bind(sock_fd, (struct sockaddr *)&addr, sizeof(addr)) != 0)
    {
        perror("bind");
    }
    else
    {
        printf("bind success\n");

        struct sockaddr_in src_addr;
        int n = 0; // 接收数的空间
        socklen_t socklen = sizeof(src_addr);
        while (1)
        {
            bzero(&src_addr, sizeof(src_addr));

            // 接收数据，如果数据未到达，则会阻塞，直到数据到达为止
            ssize_t len = recvfrom(sock_fd, &n, sizeof(n), 0, (struct sockaddr *)&src_addr, &socklen);
            if (len < 0)
            {
                perror("recvfrom");
                break;
            }

            char srcIP[INET_ADDRSTRLEN];                                           // 16
            int port = ntohs(src_addr.sin_port);                                   // 将网络字节序转化为本地字节序
            inet_ntop(AF_INET, &src_addr.sin_addr.s_addr, srcIP, INET_ADDRSTRLEN); // 将网络数字转换为点分十进制 ip

            printf("从 %s:%d 位置接收到的数字为(%lu Bytes): %d\n", srcIP, port, len, n);


            char sendbuf[128] = "";

            if (n == 1)
                strcpy(sendbuf, "disen666");
            else if (n == 2)
                strcpy(sendbuf, "jack good");
            else if (n == 3)
                strcpy(sendbuf, "disen888");
            else if (n == 4)
                strcpy(sendbuf, "bye");

            sendto(sock_fd, &sendbuf, strlen(sendbuf), 0, (struct sockaddr *)&src_addr, socklen);
            printf("发送回去内容为 %s\n", sendbuf);
        }
    }

    close(sock_fd);

    return 0;
}