UDP持续收发的C代码

UDP（User Datagram Protocol）是一种无连接的数据报协议，适用于对实时性和低延迟有较高需求的应用，如网络游戏、在线聊天等。下面是一个简单的UDP客户端和服务器的C语言示例，展示了如何持续收发数据：

// 客户端发送部分
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>

#define PORT 12345

int main() {
    struct sockaddr_in server_address;
    int client_socket = socket(AF_INET, SOCK_DGRAM, 0);

    if (client_socket == -1) {
        perror("Failed to create socket");
        return 1;
    }

    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(PORT);
    inet_pton(AF_INET, "localhost", &server_address.sin_addr); // 本地IP

    char message[] = "Hello from client";
    while (1) {
        sendto(client_socket, message, strlen(message), 0,
               (struct sockaddr *)&server_address, sizeof(server_address));
        printf("Message sent.\n");
        sleep(1); // 持续发送，间隔1秒
    }

    close(client_socket);
    return 0;
}

// 服务器接收部分
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <errno.h>

#define BUFFER_SIZE 256

void receive_data(int server_socket) {
    struct sockaddr_in client_address;
    socklen_t address_length = sizeof(client_address);
    char buffer[BUFFER_SIZE];

    while (1) {
        ssize_t bytes_received = recvfrom(server_socket, buffer, BUFFER_SIZE, 0,
                                          (struct sockaddr *)&client_address, &address_length);

        if (bytes_received > 0) {
            printf("Received message from %s: %.*s\n",
                   inet_ntoa(client_address.sin_addr),
                   (int)bytes_received, buffer);
        } else if (bytes_received == 0) {
            printf("Client disconnected.\n");
        } else {
            perror("Error receiving data");
        }
    }
}

int main() {
    int server_socket = socket(AF_INET, SOCK_DGRAM, 0);

    if (server_socket == -1) {
        perror("Failed to create socket");
        return 1;
    }

    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(PORT);
    server_address.sin_addr.s_addr = htonl(INADDR_ANY); // 静态绑定到所有接口

    bind(server_socket, (struct sockaddr *)&server_address, sizeof(server_address));

    printf("Server started on port %d.\n", ntohs(PORT));

    // 异步处理接收请求
    pid_t child_pid = fork();
    if (child_pid == 0) { // 子进程
        receive_data(server_socket);
        exit(0);
    } else if (child_pid < 0) {
        perror("Fork failed");
        exit(1);
    }

    receive_data(server_socket); // 主进程继续接收其他请求

    close(server_socket);
    return 0;
}

在这个例子中，客户端持续向服务器发送消息，而服务器在独立的子进程中监听并打印接收到的消息。