UDP文件传输程序在C中，而循环不会做任何事情

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define PORT 8888
#define BUFLEN 512

int main() {
    int sockfd;
    struct sockaddr_in servaddr, cliaddr;
    char buffer[BUFLEN];

    // 创建UDP套接字
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    memset(&servaddr, 0, sizeof(servaddr));
    memset(&cliaddr, 0, sizeof(cliaddr));

    // Filling server information
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = INADDR_ANY;
    servaddr.sin_port = htons(PORT);

    // Bind the socket with the server address
    if (bind(sockfd, (const struct sockaddr *)&servaddr, sizeof(servaddr)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    int n;
    socklen_t len;
    while (1) {
        len = sizeof(cliaddr); // len is value/result

        // 接收数据
        n = recvfrom(sockfd, (char *)buffer, BUFLEN, MSG_WAITALL, (struct sockaddr *)&cliaddr, &len);
        buffer[n] = '\0';
        printf("Server : %s\n", buffer);

        // 发送响应
        sendto(sockfd, (const char *)buffer, strlen(buffer), MSG_CONFIRM, (const struct sockaddr *)&cliaddr, len);
    }

    close(sockfd);
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

#define SERVER_IP "127.0.0.1"
#define PORT 8888
#define BUFLEN 512

int main() {
    int sockfd;
    struct sockaddr_in servaddr;
    char buffer[BUFLEN] = "Hello from client";

    // 创建UDP套接字
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    memset(&servaddr, 0, sizeof(servaddr));

    // Filling server information
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(PORT);
    servaddr.sin_addr.s_addr = inet_addr(SERVER_IP);

    int n;
    socklen_t len;

    sendto(sockfd, (const char *)buffer, strlen(buffer), MSG_CONFIRM, (const struct sockaddr *)&servaddr, sizeof(servaddr));
    printf("Message sent to server\n");

    n = recvfrom(sockfd, (char *)buffer, BUFLEN, MSG_WAITALL, (struct sockaddr *)&servaddr, &len);
    buffer[n] = '\0';
    printf("Client : %s\n", buffer);

    close(sockfd);
    return 0;
}

int running = 1;
while (running) {
    // 循环体内容
    if (/* 某些条件 */) {
        running = 0; // 设置退出条件
    }
}