linux下udp编程

在Linux下进行UDP编程，可以使用C语言的套接字（socket）编程。下面是一个简单的UDP客户端和服务器的示例，你可以参考它进行开发。

UDP客户端：

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

#define SERVER_IP "127.0.0.1"
#define SERVER_PORT 8000

int main(int argc, char *argv[])
{
    int sockfd;
    struct sockaddr_in server_addr;
    char send_buf[1024] = "Hello, UDP server!";
    char recv_buf[1024] = {0};

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("socket error");
        exit(-1);
    }

    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
    server_addr.sin_port = htons(SERVER_PORT);

    sendto(sockfd, send_buf, strlen(send_buf), 0, 
           (struct sockaddr *)&server_addr, sizeof(server_addr));

    recvfrom(sockfd, recv_buf, sizeof(recv_buf), 0, NULL, NULL);
    printf("recv from server: %s\n", recv_buf);

    close(sockfd);

    return 0;
}

UDP服务器：

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

#define SERVER_PORT 8000

int main(int argc, char *argv[])
{
    int sockfd;
    struct sockaddr_in server_addr, client_addr;
    char recv_buf[1024] = {0};
    char send_buf[1024] = "Hello, UDP client!";

    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("socket error");
        exit(-1);
    }

    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(SERVER_PORT);

    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind error");
        exit(-1);
    }

    printf("UDP server is running...\n");

    while (1) {
        socklen_t len = sizeof(client_addr);
        int n = recvfrom(sockfd, recv_buf, sizeof(recv_buf), 0, 
                         (struct sockaddr *)&client_addr, &len);
        if (n < 0) {
            perror("recvfrom error");
            continue;
        }

        printf("recv from client %s:%d : %s\n", 
               inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), recv_buf);

        sendto(sockfd, send_buf, strlen(send_buf), 0, 
               (struct sockaddr *)&client_addr, sizeof(client_addr));
    }

    close(sockfd);

    return 0;
}

这里的服务器会一直监听客户端发送的消息，并且将收到的消息原样返回给客户端。你可以在命令行中编译并运行这两个程序，然后在另一个终端中使用netcat等工具向服务器发送UDP报文，观察服务器的响应。