- 网络编程基础
网络编程，首先了解计算机网络体系结构是有必要的，着重掌握TCP、IP协议，理解socket的概念，理解数据报方式和流式套接字的原理，熟练掌握相关数据结构的使用 -
数据报和流式套接字的工作过程
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基本概念
linux操作系统一切皆文件的概念在socket通信过程中体现的十分完整，通过一个文件描述符来索引一个socket，创建socket的系统调用为
相关参数的含义可查看manual文档，其中domain比较特殊，可取下表
一般我们使用的AF_INET域中的套接字地址
- 一个简单的例子
server.c
client.c#include#include #include #include #include #include int main(){ int server_fd, client_fd; int server_addr_len, client_addr_len; struct sockaddr_in server_addr, client_addr; server_addr_len = sizeof(server_addr); server_fd = socket(AF_INET, SOCK_STREAM, 0); server_addr.sin_family = AF_INET; server_addr.sin_addr.s_addr = inet_addr("127.0.0.1"); server_addr.sin_port = 8000; bind(server_fd, (struct sockaddr *)&server_addr, server_addr_len); listen(server_fd, 5); while(1){ printf("服务器等待消息！\n"); char ch; client_addr_len = sizeof(client_addr); client_fd = accept(server_fd, (struct sockaddr *) &client_addr, (socklen_t *)&client_addr_len); read(client_fd, &ch, 1); ch++; write(client_fd, &ch, 1); close(client_fd); } return 0; } #include#include #include #include #include #include #include #include int main(){ struct sockaddr_in server_addr; int server_addr_len = sizeof(sockaddr_in); server_addr.sin_addr.s_addr = inet_addr("127.0.0.1"); server_addr.sin_family = AF_INET; server_addr.sin_port = 8000; int socket_fd = socket(AF_INET, SOCK_STREAM, 0); char ch = 'A'; int res; if((res = connect(socket_fd, (sockaddr*) &server_addr, (socklen_t) server_addr_len)) == -1){ perror("连接目的地址出错！"); exit(1); } printf("请输入字符：\n"); scanf("%c", &ch); write(socket_fd, &ch, 1); read(socket_fd, &ch, 1); printf("%c\n", ch); close(socket_fd); return 0; } - 熟悉以下用来初始化socket地址的函数
inet_ntoa/inet_aton
inet_addr
htonl/htons/ntohl/ntohs - 异步I、O之epoll
有时为了处理大量的文件句柄，需要一种机制，在单线程中也可以处理多个socket请求，轮询的机制可以实现但是对系统的负载较高，epoll是linux系统用来处理类似socket这样的文件句柄的读写等操作的一种IO复用机制。服务端维护一个socket列表，使用epoll调用来取出准备好读或写的socket，随后可以对socket句柄进行操作
用到的系统调用epoll_create/epoll_ctl/epoll_wait
用到的数据结构epoll_event/epoll_data_t
查阅manual了解函数用法
一个简单的例子
common.h
server.c//include the header file socket,io,epoll,list,string,unistd,stdlib #include#include #include #include #include #include #include -
#include
#include #include #include #include #include //namespace using namespace std; //client list, C++ stl list list client_list; //macro statement server_ip,server_port,epollsize,buf_size,Welcome string,server_string #define SERVER_IP "127.0.0.1" #define SERVER_PORT 8888 #define EPOLL_SIZE 500 #define BUF_SIZE 2048 #define WELCOME_STRING "Welcome to join the chat room, your chat ID is: Client# %d" #define SERVER_STRING "Client id #%d say >> %s" #define CAUTION "only one client in the chat room" //set fd in nonblocking io mode, using fnctl void setNonBlocking(int fd){ int res = fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | O_NONBLOCK); if(res != 0){ perror("set fd nonblock failed"); return; } } //add fd to the epoll,with epoll_ctl void addFdToEpoll(int epollfd, int sockfd, bool enable_et){ struct epoll_event event; event.events = EPOLLIN; if(enable_et){ event.events = EPOLLIN | EPOLLET; } event.data.fd = sockfd; if(epoll_ctl(epollfd, EPOLL_CTL_ADD, sockfd, &event) != 0){ perror("add fd to epoll failed"); }; setNonBlocking(sockfd); } //send broadcast message to the client in clients list, except for which we received the data void sendBroadcastMessage(int sockfd){ char buf[BUF_SIZE], message[BUF_SIZE]; //initialize the space bzero(buf, BUF_SIZE); bzero(message, BUF_SIZE); int rlen = recv(sockfd, buf, BUF_SIZE, 0); printf("read data from Client #%d: %s\n", sockfd, buf); if(rlen == 0){ close(sockfd); client_list.remove(sockfd); printf("client #%ld closed, Now, there are %d clients in the chatroom\n",sockfd, client_list.size()); }else{ if(client_list.size() == 1){ int slen = send(sockfd, CAUTION, strlen(CAUTION), 0); return; } sprintf(message, SERVER_STRING, sockfd, buf); printf("will send:%s\n", message); list ::iterator iter; for( iter = client_list.begin(); iter != client_list.end(); iter++ ){ puts("sending data..."); if(*iter != sockfd){ send(*iter, message, BUF_SIZE, 0); } } } }
client.c#include "common.h" int main(){ //socket address statement struct sockaddr_in server_addr; //initialize the address server_addr.sin_addr.s_addr = inet_addr(SERVER_IP); server_addr.sin_port = htons(SERVER_PORT); server_addr.sin_family = AF_INET; //create server socket int listener = socket(AF_INET, SOCK_STREAM, 0); //bind the server address if(bind(listener, (struct sockaddr*)&server_addr, sizeof(server_addr)) != 0){ perror("bind failed"); return 1; } //listen on the address if(listen(listener, 5) != 0){ perror("listen failed"); return 2; } //create epoll int epollfd = epoll_create(EPOLL_SIZE); if(epollfd < 0){ perror("create epollfd failed"); return 3; } //add server fd to epoll addFdToEpoll(epollfd, listener, true); //epoll_event array static struct epoll_event events[EPOLL_SIZE]; //main loop int clientfd; while(1){ //epoll_wait puts("waiting clients..."); int event_count = epoll_wait(epollfd,events, EPOLL_SIZE, -1); printf("epoll event count is %d\n", event_count); for(int i = 0; i< event_count; i++){ clientfd = events[i].data.fd; //if fd is serverfd, accept a connection, print information, add new sockfd to epoll if(clientfd == listener){ struct sockaddr_in client_addr; socklen_t addrlen = sizeof(struct sockaddr_in); int newfd = accept(listener, (struct sockaddr*)&client_addr, &addrlen); if(newfd < 0){ perror("accept new connections failed"); exit(EXIT_FAILURE); } printf( "new connection from %s:%d, client id #%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), newfd ); addFdToEpoll(epollfd, newfd, true); client_list.push_back(newfd); printf("welcome message\n"); char message[BUF_SIZE]; bzero(message, BUF_SIZE); sprintf(message, WELCOME_STRING, newfd); send(newfd, message, strlen(message), 0); }//if not, sendbroadcast message else{ sendBroadcastMessage(clientfd); } } } }#include"common.h" int main(){ //server address statement struct sockaddr_in server_addr; //initilize server address server_addr.sin_family = AF_INET; server_addr.sin_port = htons(SERVER_PORT); server_addr.sin_addr.s_addr = inet_addr(SERVER_IP); //create sock int sock = socket(AF_INET, SOCK_STREAM, 0); if(sock < 0){ perror("create socket failed"); return 1; } if(connect(sock, (struct sockaddr*)&server_addr, sizeof(struct sockaddr_in)) != 0){ perror("connect server failed"); return 0; } int pipefd[2]; if(pipe(pipefd) != 0){ perror("create pipe failed"); return 2; } int epollfd = epoll_create(EPOLL_SIZE); if(epollfd< 0){ perror("create epollfd failed"); return 3; } addFdToEpoll(epollfd, sock, true); addFdToEpoll(epollfd, pipefd[0], true); pid_t pid = fork(); if(pid < 0){ perror("create child process failed"); return 4; } int client_running = 1; char message[BUF_SIZE]; char buf[BUF_SIZE]; struct epoll_event events[2]; if(pid == 0){ close(pipefd[0]); printf("please input your message, and type exit to terminate\n"); while(client_running){ //printf("input>"); bzero(message, BUF_SIZE); //bzero(buf, BUF_SIZE); fgets(message, BUF_SIZE, stdin); if(strncmp(message, "exit", strlen("exit")) == 0){ client_running = 0; close(sock); close(pipefd[1]); return 0; }else{ write(pipefd[1], message, strlen(message)); } } }else{ close(pipefd[1]); while(client_running){ int event_count = epoll_wait(epollfd, events, 2, -1); for(int i = 0; i < event_count; i++){ if(events[i].data.fd == pipefd[0]){ bzero(buf, BUF_SIZE); if(read(pipefd[0], buf, BUF_SIZE) == 0){ client_running = 0; }else{ printf("\nyour input:%s\n", buf); send(sock, buf, strlen(buf) - 1, 0); } }else{ recv(sock, buf, BUF_SIZE, 0); printf("\nServer message:%s\n", buf); } } } } close(sock); if(pid){ close(pipefd[0]); }else{ close(pipefd[1]); } return 0; } - 异步IO之libevent事件框架
事件驱动相比较于轮询更有效
参见libevent文档
