第1关：UDP套接字创建与端口绑定
#include <sys/types.h>#include <sys/socket.h>#include <arpa/inet.h>#include <stdio.h>#include <errno.h>#include <string.h>/************************ * port: 需要绑定的端口号 * 返回值: 调用成功返回0，否则返回-1*************************/int UDPSocket(unsigned short port){int ret = -1;/********** BEGIN **********/int sockfd; struct sockaddr_in server_addr; // 创建UDP套接字 sockfd = socket(AF_INET, SOCK_DGRAM, 0); if (sockfd == -1) { printf("创建UDP套接字失败: %s\n", strerror(errno)); return -1; } // 初始化服务器地址结构体 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(port); // 绑定端口 ret = bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)); if (ret == -1) { printf("绑定端口失败: %s\n", strerror(errno)); close(sockfd); return -1; } ret = 0;/********** END **********/return ret;}
第2关：UDP数据传送
#include <sys/types.h>#include <sys/socket.h>#include <arpa/inet.h>#include <stdio.h>#include <errno.h>#include <string.h>#include <unistd.h>#define PORT 8888int main(){int sockfd;sockfd = socket(AF_INET, SOCK_DGRAM, 0);if(sockfd == -1){return -1;}struct sockaddr_in addr;bzero(&addr, sizeof(addr)); //清空addr.sin_family = AF_INET;addr.sin_port = htons(PORT);addr.sin_addr.s_addr = htonl(INADDR_ANY);//与PORT端口进行绑定if(bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) == -1){return -1;}char data[100];//接收客户端传来的数据，并打印出来(提示：换行打印)//同时将接收到的数据原样发送给客户端//当接收到"exit"字符串时，退出当前程序，不打印出"exit"字符串//提示：在每次接收字符串前要将存放字符串的变量清空/********** BEGIN **********/struct sockaddr_in clientAddr; socklen_t clientAddrLen = sizeof(clientAddr); while (1) { // 每次接收前清空存放字符串的变量 memset(data, 0, sizeof(data)); ssize_t recvLen = recvfrom(sockfd, data, sizeof(data), 0, (struct sockaddr *)&clientAddr, &clientAddrLen); if (recvLen == -1) { printf("接收数据失败: %s\n", strerror(errno)); continue; } else if (recvLen > 0) { // 去掉字符串末尾可能的换行符等空白字符 while (data[recvLen - 1] == '\n' || data[recvLen - 1] == '\r' || data[recvLen - 1] == '\t' || data[recvLen - 1] == ' ') { data[recvLen - 1] = '\0'; recvLen--; } if (strcmp(data, "exit") == 0) { break; } // 换行打印接收到的数据 printf("%s\n", data); // 将接收到的数据原样发送给客户端 ssize_t sendLen = sendto(sockfd, data, recvLen, 0, (struct sockaddr *)&clientAddr, clientAddrLen); if (sendLen == -1) { printf("发送数据失败: %s\n", strerror(errno)); } } }/********** END **********/close(sockfd);return 0;}
第3关：项目实战
#include <stdio.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <string.h>#include <errno.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <unistd.h>//定义数据块大小char data[16];//定义服务器端口和服务器地址#define PORT 8889#define SERVER_IP "127.0.0.1"int main(int argc, char *argv[]){int sockfd;sockfd = socket(AF_INET, SOCK_DGRAM, 0);if(sockfd == -1){return -1;}struct sockaddr_in servAddr;int servAddrLen = sizeof(servAddr);bzero(&servAddr, sizeof(servAddr));servAddr.sin_family = AF_INET;servAddr.sin_port = htons(PORT);servAddr.sin_addr.s_addr = inet_addr(SERVER_IP);//由用户传入的要下载文件的名称char *downLoadFileName = argv[1];printf("%s\n", argv[1]);//先在本地创建要下载的文件int fd = fd = open(downLoadFileName, O_CREAT | O_WRONLY | O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);//向服务器发送要上传文件的名称sendto(sockfd, downLoadFileName, strlen(downLoadFileName), 0, (struct sockaddr *)&servAddr, servAddrLen); /********** BEGIN **********/char ack[16]; int recvLen; // 循环接收服务器发送的数据块 while (1) { // 接收服务器发送的数据块 recvLen = recvfrom(sockfd, data, sizeof(data), 0, (struct sockaddr *)&servAddr, &servAddrLen); if (recvLen == -1) { printf("接收数据失败: %s\n", strerror(errno)); continue; } // 根据数据块类型判断是否下载完成 if (data[0] == 'e') { // 下载完成，关闭文件并退出程序 close(fd); break; } else if (data[0] == 'c') { // 数据块为文件内容，将内容写入本地文件 write(fd, &(data[1]), recvLen - 1); } // 向服务器发送接收确认请求 sendto(sockfd, "OK", strlen("OK"), 0, (struct sockaddr *)&servAddr, servAddrLen); // 清空数据块数据部分（除了类型标识字节） memset(&(data[1]), 0, sizeof(data) - 1); }/********** END **********/close(sockfd);return 0;}