#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>#define SERVER_PORT 8888
#define BUFF_LEN 1024void handle_udp_msg(int fd)
{char buf[BUFF_LEN];  //接收缓冲区，1024字节
    socklen_t len;int count;struct sockaddr_in clent_addr;  //clent_addr用于记录发送方的地址信息while(1){memset(buf, 0, BUFF_LEN);len = sizeof(clent_addr);count = recvfrom(fd, buf, BUFF_LEN, 0, (struct sockaddr*)&clent_addr, &len);  //recvfrom是拥塞函数，没有数据就一直拥塞if(count == -1){printf("recieve data fail!\n");return;}printf("client:%s\n",buf);  //打印client发过来的信息memset(buf, 0, BUFF_LEN);sprintf(buf, "I have recieved %d bytes data!\n", count);  //回复clientprintf("server:%s\n",buf);  //打印自己发送的信息给sendto(fd, buf, BUFF_LEN, 0, (struct sockaddr*)&clent_addr, len);  //发送信息给client，注意使用了clent_addr结构体指针
}
}/*server:socket-->bind-->recvfrom-->sendto-->close
*/int main(int argc, char* argv[])
{int server_fd, ret;struct sockaddr_in ser_addr; server_fd = socket(AF_INET, SOCK_DGRAM, 0); //AF_INET:IPV4;SOCK_DGRAM:UDPif(server_fd < 0){printf("create socket fail!\n");return -1;}memset(&ser_addr, 0, sizeof(ser_addr));ser_addr.sin_family = AF_INET;ser_addr.sin_addr.s_addr = htonl(INADDR_ANY); //IP地址，需要进行网络序转换，INADDR_ANY：本地地址ser_addr.sin_port = htons(SERVER_PORT);  //端口号，需要网络序转换
ret = bind(server_fd, (struct sockaddr*)&ser_addr, sizeof(ser_addr));if(ret < 0){printf("socket bind fail!\n");return -1;}handle_udp_msg(server_fd);   //处理接收到的数据
close(server_fd);return 0;
}

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>#define SERVER_PORT 8888
#define BUFF_LEN 512
#define SERVER_IP "172.0.5.182"void udp_msg_sender(int fd, struct sockaddr* dst)
{socklen_t len;struct sockaddr_in src;while(1){char buf[BUFF_LEN] = "TEST UDP MSG!\n";len = sizeof(*dst);printf("client:%s\n",buf);  //打印自己发送的信息sendto(fd, buf, BUFF_LEN, 0, dst, len);memset(buf, 0, BUFF_LEN);recvfrom(fd, buf, BUFF_LEN, 0, (struct sockaddr*)&src, &len);  //接收来自server的信息printf("server:%s\n",buf);sleep(1);  //一秒发送一次消息
    }
}/*client:socket-->sendto-->revcfrom-->close
*/int main(int argc, char* argv[])
{int client_fd;struct sockaddr_in ser_addr;client_fd = socket(AF_INET, SOCK_DGRAM, 0);if(client_fd < 0){printf("create socket fail!\n");return -1;}memset(&ser_addr, 0, sizeof(ser_addr));ser_addr.sin_family = AF_INET;//ser_addr.sin_addr.s_addr = inet_addr(SERVER_IP);ser_addr.sin_addr.s_addr = htonl(INADDR_ANY);  //注意网络序转换ser_addr.sin_port = htons(SERVER_PORT);  //注意网络序转换
udp_msg_sender(client_fd, (struct sockaddr*)&ser_addr);close(client_fd);return 0;
}