linux 系统udp编程实例

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

#define BUFLEN 512  // 缓冲区大小
#define PORT 8888   // 监听端口

int main() {
    struct sockaddr_in si_me, si_other;
    int s, slen = sizeof(si_other);
    char buf[BUFLEN];

    // 创建UDP socket
    if ((s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 绑定socket到端口
    memset((char *)&si_me, 0, sizeof(si_me));
    si_me.sin_family = AF_INET;
    si_me.sin_port = htons(PORT);
    si_me.sin_addr.s_addr = htonl(INADDR_ANY);

    if (bind(s, (struct sockaddr*)&si_me, sizeof(si_me)) == -1) {
        perror("bind");
        close(s);
        exit(EXIT_FAILURE);
    }

    // 接收数据
    while (1) {
        memset(buf, 0, BUFLEN);
        if (recvfrom(s, buf, BUFLEN, 0, (struct sockaddr *)&si_other, &slen) == -1) {
            perror("recvfrom()");
            exit(EXIT_FAILURE);
        }
        printf("Received packet from %s:%d\nData: %s\n", inet_ntoa(si_other.sin_addr), ntohs(si_other.sin_port), buf);

        // 发送回复
        sendto(s, buf, strlen(buf), 0, (struct sockaddr*)&si_other, slen);
    }

    close(s);
    return 0;
}

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

#define SERVER "127.0.0.1"  // 服务器IP地址
#define BUFLEN 512         // 缓冲区大小
#define PORT 8888          // 服务器端口

int main(int argc, char *argv[]) {
    struct sockaddr_in si_other;
    int s, slen = sizeof(si_other);
    char buf[BUFLEN];
    char message[BUFLEN];

    if (argc != 2) {
        fprintf(stderr, "Usage: %s <message>\n", argv[0]);
        exit(1);
    }

    // 创建UDP socket
    if ((s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 设置服务器地址
    memset((char *)&si_other, 0, sizeof(si_other));
    si_other.sin_family = AF_INET;
    si_other.sin_port = htons(PORT);

    if (inet_aton(SERVER, &si_other.sin_addr) == 0) {
        fprintf(stderr, "inet_aton() failed\n");
        exit(1);
    }

    // 发送消息
    strcpy(message, argv[1]);
    if (sendto(s, message, strlen(message), 0, (struct sockaddr*)&si_other, slen) == -1) {
        perror("sendto()");
        exit(EXIT_FAILURE);
    }

    // 接收回复
    if (recvfrom(s, buf, BUFLEN, 0, (struct sockaddr *)&si_other, &slen) == -1) {
        perror("recvfrom()");
        exit(EXIT_FAILURE);
    }
    printf("Received reply: %s\n", buf);

    close(s);
    return 0;
}