练习：

服务器：

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pthread.h>
#include <semaphore.h>
#include <wait.h>
#include <signal.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <semaphore.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <sys/un.h>
#include <head.h>
#include <sqlite3.h>
typedef struct sockaddr_in addr_in_t;
typedef struct sockaddr addr_t;
typedef struct sockaddr_un addr_un_t;enum Type {TYPE_REGIST = 1,TYPE_LOGIN
};enum Operation {SUCCESS = 1,ERR
};typedef struct Pack {enum Type type;enum Operation op;char name[20];char pswd[20];
} pack_t;void client_regist(sqlite3* db, pack_t pack, int client) {char* sql = "insert into stu(name,pswd) values(?,?)";sqlite3_stmt* stmt = NULL;sqlite3_prepare_v2(db, sql, -1, &stmt, 0);sqlite3_bind_text(stmt, 1, pack.name, -1, 0);sqlite3_bind_text(stmt, 2, pack.pswd, -1, 0);int res = sqlite3_step(stmt);if (res != SQLITE_DONE && res != SQLITE_ROW) {pack.op = ERR;} else {pack.op = SUCCESS;}write(client, &pack, sizeof(pack));sqlite3_finalize(stmt); 
}void client_login(sqlite3* db, pack_t pack, int client) {char* sql = "select pswd from stu where name = ?";sqlite3_stmt* stmt = NULL;sqlite3_prepare_v2(db, sql, -1, &stmt, 0);sqlite3_bind_text(stmt, 1, pack.name, -1, 0);int res = sqlite3_step(stmt);if (res == SQLITE_DONE) {pack.op = ERR;} else if (res == SQLITE_ROW) {const char* db_pswd = sqlite3_column_text(stmt, 0);if (strcmp(db_pswd, pack.pswd) == 0) {pack.op = SUCCESS;} else {pack.op = ERR;}}write(client, &pack, sizeof(pack));sqlite3_finalize(stmt); 
}int main(int argc, const char *argv[]) {if (argc < 2) {printf("请输入端口号\n");return 1;}int port = atoi(argv[1]);sqlite3* db = NULL;sqlite3_open("./stu.db", &db);int server = socket(AF_INET, SOCK_STREAM, 0);struct sockaddr_in addr = {0};addr.sin_family = AF_INET;addr.sin_port = htons(port);addr.sin_addr.s_addr = inet_addr("0.0.0.0");if (bind(server, (struct sockaddr*)&addr, sizeof(addr)) == -1) {perror("bind");return 1;}listen(server, 50);int epfd = epoll_create1(EPOLL_CLOEXEC);int count = 0;struct epoll_event server_ev = {0};server_ev.events = EPOLLIN;server_ev.data.fd = server;epoll_ctl(epfd, EPOLL_CTL_ADD, server, &server_ev);count++;struct epoll_event stdin_ev = {0};stdin_ev.events = EPOLLIN;stdin_ev.data.fd = 0;epoll_ctl(epfd, EPOLL_CTL_ADD, 0, &stdin_ev);count++;while (1) {struct epoll_event list[count];memset(list, 0, sizeof(list));int res = epoll_wait(epfd, list, count, -1);for (int i = 0; i < res; i++) {int fd = list[i].data.fd;if (fd == server) {int client = accept(server, 0, 0);printf("有新客户端连接\n");struct epoll_event client_ev = {0};client_ev.events = EPOLLIN | EPOLLET;client_ev.data.fd = client;epoll_ctl(epfd, EPOLL_CTL_ADD, client, &client_ev);count++;} else if (fd == 0) {char buf[64] = "";scanf("%s", buf);getchar();printf("键盘输入数据:%s\n", buf);} else {pack_t pack = {0};int client = fd;int res = read(client, &pack, sizeof(pack));if (res == 0) {printf("客户端断开连接\n");epoll_ctl(epfd, EPOLL_CTL_DEL, fd, 0);close(fd);break;}if (pack.type == TYPE_REGIST) {client_regist(db, pack, client);} else if (pack.type == TYPE_LOGIN) {client_login(db, pack, client);}}}}sqlite3_close(db);return 0;
}

客户端

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pthread.h>
#include <semaphore.h>
#include <wait.h>
#include <signal.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <semaphore.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <sys/un.h>
#include <head.h>
#include <sqlite3.h>
typedef struct sockaddr_in addr_in_t;
typedef struct sockaddr addr_t;
typedef struct sockaddr_un addr_un_t;enum Type {TYPE_REGIST = 1,TYPE_LOGIN
};enum Operation {SUCCESS = 1,ERR
};typedef struct Pack {enum Type type;enum Operation op;char name[20];char pswd[20];
} pack_t;void* thread_main(void* arg) {int client = *(int*)arg;while (1) {pack_t pack = {0};int res = read(client, &pack, sizeof(pack));if (res == 0) break;printf("接收到服务器回包\n");if (pack.type == TYPE_REGIST) {if (pack.op == ERR) {printf("该账号已存在\n");} else {printf("注册成功\n");}} else if (pack.type == TYPE_LOGIN) {if (pack.op == ERR) {printf("账号或密码错误\n");} else {printf("登录成功\n");}}}return NULL;
}int main(int argc, const char *argv[]) {if (argc < 2) {printf("请输入端口号\n");return 1;}int port = atoi(argv[1]);int client = socket(AF_INET, SOCK_STREAM, 0);struct sockaddr_in addr = {0};addr.sin_family = AF_INET;addr.sin_port = htons(port);addr.sin_addr.s_addr = inet_addr("127.0.0.1"); if (connect(client, (struct sockaddr*)&addr, sizeof(addr)) == -1) {perror("connect");return 1;}pthread_t id;pthread_create(&id, 0, thread_main, &client);pthread_detach(id);while (1) {int ch = 0;pack_t pack = {0};printf("1:注册\n");printf("2:登录\n");printf("请选择:");scanf("%d", &ch);getchar();if (ch == 1) {pack.type = TYPE_REGIST;} else if (ch == 2) {pack.type = TYPE_LOGIN;}printf("请输入账号:");scanf("%s", pack.name);getchar();printf("请输入密码:");scanf("%s", pack.pswd);getchar();write(client, &pack, sizeof(pack));}return 0;
}