要求：1.有新用户登录，其他在线的用户可以收到登录信息

           2.有用户群聊，其他在线的用户可以收到群聊信息

           3.有用户退出，其他在线的用户可以收到退出信息

           4.服务器可以发送系统信息

效果图：

service.c

#include <head.h>
typedef struct _MSG
{char type; // 类型  'L' 登录  'C' 群聊  'Q' 退出char name[32];char txt[128];
} msg_t;
typedef struct _NODE
{struct sockaddr_in clientaddr;struct _NODE *next;
} node_t;
void create_node(node_t **p);
void do_login(node_t *phead, msg_t msg, int sockfd, struct sockaddr_in clientaddr);
void do_chat(node_t *phead, msg_t msg, int sockfd, struct sockaddr_in clientaddr);
void do_quit(node_t *phead, msg_t msg, int sockfd, struct sockaddr_in clientaddr);int main(int argc, const char *argv[])
{// 入参合理性检查if (argc != 3){printf("usage error:%s <ip> <port>...\n", argv[0]);exit(-1);}int sockfd = 0;// 创建套接字if (-1 == (sockfd = socket(AF_INET, SOCK_DGRAM, 0))){perror("socket error");exit(-1);}// 填充服务器网络信息结构体struct sockaddr_in serveraddr;socklen_t serveraddr_len = sizeof(serveraddr);memset(&serveraddr, 0, sizeof(serveraddr));serveraddr.sin_family = AF_INET;serveraddr.sin_addr.s_addr = inet_addr(argv[1]);serveraddr.sin_port = htons(atoi(argv[2]));struct sockaddr_in clientaddr;socklen_t clientaddr_len = sizeof(clientaddr);// 绑定if (-1 == (bind(sockfd, (struct sockaddr *)&serveraddr, serveraddr_len))){perror("bind error");exit(-1);}node_t *phead = NULL;create_node(&phead);msg_t msg;// 收发数据char buff[128] = {0};pid_t pid = 0;pid = fork();if (pid == -1){perror("fork error");exit(-1);}else if (pid == 0){// 子进程用于接收数据while (1){memset(&msg, 0, sizeof(msg));if (-1 == recvfrom(sockfd, &msg, sizeof(msg), 0, (struct sockaddr *)&clientaddr, &clientaddr_len)){perror("recvfrom error");exit(-1);}printf("%s:%s\n", msg.name, msg.txt);switch (msg.type){case 'L':do_login(phead, msg, sockfd, clientaddr);break;case 'C':do_chat(phead, msg, sockfd, clientaddr);break;case 'Q':do_quit(phead, msg, sockfd, clientaddr);break;}}}else if (pid > 0){// 父进程用于发送数据// 把父进程当做一个客户端 以群聊的方式 把系统消息发给子进程strcpy(msg.name, "server");msg.type = 'C';while (1){memset(msg.txt, 0, 128);fgets(msg.txt, sizeof(msg.txt), stdin);msg.txt[strlen(msg.txt) - 1] = '\0';if (-1 == sendto(sockfd, &msg, sizeof(msg), 0, (struct sockaddr *)&serveraddr, serveraddr_len)){perror("sento error");exit(-1);}}}close(sockfd);return 0;
}void create_node(node_t **p)
{*p = (node_t *)malloc(sizeof(node_t));memset(*p, 0, sizeof(node_t));
}
// 登录操作函数
void do_login(node_t *phead, msg_t msg, int sockfd, struct sockaddr_in clientaddr)
{// 遍历链表 当前在线的所有人发“***加入了群聊”的消息node_t *ptemp = phead;while (ptemp->next != NULL){ptemp = ptemp->next;if (-1 == sendto(sockfd, &msg, sizeof(msg), 0, (struct sockaddr *)&(ptemp->clientaddr), sizeof(ptemp->clientaddr))){perror("sento error");exit(-1);}}// 把新加入的群聊客户端网络信息结构体加入到链表中node_t *pnew = NULL;create_node(&pnew);pnew->clientaddr = clientaddr;pnew->next = phead->next;phead->next = pnew;return;
}
void do_chat(node_t *phead, msg_t msg, int sockfd, struct sockaddr_in clientaddr)
{// 遍历链表 将群聊的消息 发给除了自己之外的所有人node_t *ptemp = phead;while (ptemp->next != NULL){ptemp = ptemp->next;if (memcmp(&clientaddr, &(ptemp->clientaddr), sizeof(clientaddr)) != 0){if (-1 == sendto(sockfd, &msg, sizeof(msg), 0, (struct sockaddr *)&(ptemp->clientaddr), sizeof(ptemp->clientaddr))){perror("sento error");exit(-1);}}}return;
}
void do_quit(node_t *phead, msg_t msg, int sockfd, struct sockaddr_in clientaddr)
{// 把 xxx 退出群聊的消息 发给在线的除自己的所有人  并且将自己在链表中删除node_t *ptemp = phead;while (ptemp->next != NULL){if (memcmp(&clientaddr, &(ptemp->next->clientaddr), sizeof(clientaddr)) != 0){if (-1 == sendto(sockfd, &msg, sizeof(msg), 0, (struct sockaddr *)&(ptemp->next->clientaddr), sizeof(ptemp->next->clientaddr))){perror("sento error");exit(-1);}ptemp = ptemp->next;}else{node_t *pdel = ptemp->next;ptemp->next = pdel->next;free(pdel);pdel = NULL;}}return;
}

client.c

#include <head.h>
typedef struct _MSG
{char type; // 类型  'L' 登录  'C' 群聊  'Q' 退出char name[32];char txt[128];
} msg_t;int main(int argc, const char *argv[])
{// 入参合理性检查if (argc != 3){printf("usage error:%s <ip> <port>...\n", argv[0]);exit(-1);}int sockfd = 0;// 创建套接字if (-1 == (sockfd = socket(AF_INET, SOCK_DGRAM, 0))){perror("socket error");exit(-1);}// 填充服务器网络信息结构体struct sockaddr_in serveraddr;socklen_t serveraddr_len = sizeof(serveraddr);memset(&serveraddr, 0, sizeof(serveraddr));serveraddr.sin_family = AF_INET;serveraddr.sin_addr.s_addr = inet_addr(argv[1]);serveraddr.sin_port = htons(atoi(argv[2]));msg_t msg;memset(&msg, 0, sizeof(msg));printf("请输入用户名：");fgets(msg.name, sizeof(msg.name), stdin);msg.name[strlen(msg.name) - 1] = '\0';msg.type = 'L';strcpy(msg.txt, "加入群聊");if (-1 == sendto(sockfd, &msg, sizeof(msg), 0, (struct sockaddr *)&serveraddr, serveraddr_len)){perror("sendto error");exit(-1);}// 收发数据char buff[128] = {0};pid_t pid;pid = fork();if (pid == -1){perror("fork error");exit(-1);}else if (pid == 0){// 子进程用于接收数据while (1){memset(&msg, 0, sizeof(msg));if (-1 == recvfrom(sockfd, &msg, sizeof(msg), 0, NULL, NULL)){perror("recvfrom error");exit(-1);}printf("%s : %s\n", msg.name, msg.txt);}}else if(pid>0){// //父进程 在终端获取数据 发给服务器while (1){memset(msg.txt, 0, sizeof(msg.txt));fgets(msg.txt, 128,stdin);msg.txt[strlen(msg.txt) - 1] = '\0';if (strcmp(msg.txt, "quit") == 0){msg.type = 'Q';strcpy(msg.txt, "退出群聊");}else{msg.type = 'C';}if (-1 == sendto(sockfd, &msg, sizeof(msg), 0, (struct sockaddr *)&serveraddr, serveraddr_len)){perror("sendto error");exit(-1);}if ('Q' == msg.type){// 父进程退出之前先给子进程发信号 杀死子进程kill(pid, SIGKILL);wait(NULL);break;}}}close(sockfd);return 0;
}