UDP 基本通信框架

概述

UDP（User Datagram Protocol）用户数据报协议。是一种无需建立连接就可以发送封装的 IP 数据包的方法。

UDP 开发基本框架：

服务端：

• socket
• bind
• recvfrom

客户端：

• socket
• sendto

服务端示例

文件名: udp_server.c

#include <sys/socket.h> /* included for socket */
#include <arpa/inet.h> /* included for sockaddr */
#include <stdbool.h> /* included for true */
#include <stdint.h> /* included for uint8_t */
#include <stdio.h> /* included for printf */
#include <string.h> /* included for memeset */
#include <unistd.h> /* included for close */

int main(int argc, char const *argv[])
{
    
    /* socket */
    int fd = socket(AF_INET, SOCK_DGRAM, 0);

    /* bind */
    struct sockaddr_in localaddr;
    memset(&localaddr, 0x00, sizeof(localaddr));
    localaddr.sin_family = AF_INET;
    localaddr.sin_port = htons(50352);
    localaddr.sin_addr.s_addr = inet_addr("0.0.0.0");
    bind(fd, (const struct sockaddr *)&localaddr, sizeof(localaddr));

    /* recvfrom */
    uint8_t data[1024] = {
    0x00};
    struct sockaddr_in peeraddr;
    socklen_t peerlen = sizeof(peeraddr);
    ssize_t len = 0;
    while (true) {
    
        len = recvfrom(fd, data, sizeof(data), 0, (struct sockaddr *)&peeraddr,
                       &peerlen);
        printf("recvfrom %s:%d with %ld bytes\n", inet_ntoa(peeraddr.sin_addr),
               ntohs(peeraddr.sin_port), len);
    }

    close(fd);
    return 0;
}

编译命令：

gcc -o server udp_server.c

客户端示例

文件名：udp_client.c

#include <sys/socket.h> /* included for socket */
#include <arpa/inet.h> /* included for sockaddr */
#include <stdbool.h> /* included for true */
#include <stdint.h> /* included for uint8_t */
#include <stdio.h> /* included for printf */
#include <string.h> /* included for memeset */
#include <unistd.h> /* included for close */

int main(int argc, char const *argv[])
{
    
    /* socket */
    int fd = socket(AF_INET, SOCK_DGRAM, 0);

    uint8_t data[8] = {
    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07};

    /* sendto */
    struct sockaddr_in addr;
    memset(&addr, 0x00, sizeof(addr));
    addr.sin_family = AF_INET;  // Address family
    addr.sin_port = htons(50352);
    addr.sin_addr.s_addr = inet_addr("10.133.5.170");
    ssize_t len = sendto(fd, data, sizeof(data), 0, (const struct sockaddr *)&addr,
                  sizeof(addr));
    close(fd);
    return 0;
}

编译命令：

gcc -o client udp_client.c