ntp服务端c语言代码

以下是一个简单的基于C语言的NTP服务器端代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define NTP_PORT 123
#define NTP_PACKET_SIZE 48
#define NTP_UNIX_OFFSET 2208988800UL

void sendNTPResponse(int sockfd, struct sockaddr_in* client_addr) {
    char buffer[NTP_PACKET_SIZE] = {0};
    memset(buffer, 0, NTP_PACKET_SIZE);

    // Set the Leap Indicator, Version Number, and Mode values
    buffer[0] = 0b00100011; // LI = 0, VN = 4, Mode = 3 (Server)

    // Set the Transmit Timestamp to the current time
    time_t current_time = time(NULL) + NTP_UNIX_OFFSET;
    *(uint32_t*)(buffer + 40) = htonl(current_time);

    // Send the NTP response packet to the client
    sendto(sockfd, buffer, NTP_PACKET_SIZE, 0,
           (struct sockaddr*)client_addr, sizeof(struct sockaddr_in));
}

int main() {
    int sockfd;
    struct sockaddr_in server_addr, client_addr;

    // Create a UDP socket
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("Failed to create socket");
        exit(EXIT_FAILURE);
    }

    // Bind the socket to port 123 and any available interface
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(NTP_PORT);

    if (bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        perror("Failed to bind socket");
        exit(EXIT_FAILURE);
    }

    // Main server loop
    while (1) {
        socklen_t client_addr_len = sizeof(client_addr);
        char buffer[NTP_PACKET_SIZE];

        // Receive request packet from client
        ssize_t n = recvfrom(sockfd, buffer, sizeof(buffer), 0,
                             (struct sockaddr*)&client_addr, &client_addr_len);

        if (n < 0) {
            perror("Failed to receive packet");
            continue;
        }

        // Process NTP request and send response
        sendNTPResponse(sockfd, &client_addr);
    }

    // Close the socket
    close(sockfd);

    return 0;
}

这是一个简单的NTP服务器端代码示例，它创建一个UDP socket并将其绑定到端口123。当接收到来自客户端的NTP请求时，服务器将发送NTP响应包含当前时间戳。

请注意，这只是一个简单的示例，并没有处理NTP协议的所有细节和错误情况。在实际应用中，可能需要更多的错误处理和协议细节的处理。