1. 說明：

此篇博客主要記錄一種客戶端實現方式，和兩種使用poll或者epoll分別創建echo服務器的方式，具體可看代碼注釋：

2. 相關代碼：

2.1 echoClient.cpp

#include <iostream>
#include <cstdio>
#include <cstring>#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>#define ERR_EXIT(m) \do {\perror(m); \exit(EXIT_FAILURE); \} while(0)int main() {int sock;struct sockaddr_in svrAddr, localAddr;socklen_t addrlen = sizeof(sockaddr);sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);if (sock < 0)ERR_EXIT("socket");memset(&svrAddr, 0, sizeof(svrAddr));svrAddr.sin_family = AF_INET;svrAddr.sin_port = htons(8888);svrAddr.sin_addr.s_addr = inet_addr("127.0.0.1");if (connect(sock, (sockaddr *)&svrAddr, sizeof(svrAddr)) < 0)ERR_EXIT("connect");if (getsockname(sock, (sockaddr *)&localAddr, &addrlen) < 0)ERR_EXIT("getsockname");std::cout << "ip = " << inet_ntoa(localAddr.sin_addr)<< " port = " << ntohs(localAddr.sin_port) << std::endl;char sendBuf[1024] = {0};char recvBuf[1024] = {0};while (fgets(sendBuf, sizeof(sendBuf), stdin) != NULL){write(sock, sendBuf, strlen(sendBuf));read(sock, recvBuf, sizeof(recvBuf));fputs(recvBuf, stdout);memset(sendBuf, 0, sizeof(sendBuf));memset(recvBuf, 0, sizeof(recvBuf));}close(sock);return 0;
}

2.2 echoServer_poll.cpp

#include <iostream>
#include <vector>
#include <string>#include <cstdio>
#include <cstring>#include <arpa/inet.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <unistd.h>#include <signal.h>
#include <poll.h>
#include <sys/socket.h>#define ERR_EXIT(m) \do {\perror(m); \exit(EXIT_FAILURE); \} while(0)using PollfdList = std::vector<pollfd>;int main()
{//忽略系統提示的一些錯誤信號/*signal(para1,para2)para1:信號類型para2:信號處理函數(可以自定義)講解參考：https://blog.csdn.net/u013271656/article/details/114537411*/signal(SIGPIPE, SIG_IGN);signal(SIGCHLD, SIG_IGN);//創建一個監聽套接字(非阻塞套接字)int listenfd;listenfd = socket(PF_INET, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, IPPROTO_TCP);if(listenfd < 0){ERR_EXIT("socket");}//設置地址struct sockaddr_in srvAddr;memset(&srvAddr,0,sizeof(srvAddr));//初始化srvAddr.sin_family = AF_INET;srvAddr.sin_port = htons(8888);srvAddr.sin_addr.s_addr = htonl(INADDR_ANY);//設置地址的重復利用int on = 1;if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0){ERR_EXIT("setsockopt");}//綁定if(bind(listenfd, (sockaddr *)&srvAddr, sizeof(srvAddr)) < 0){ERR_EXIT("bind");}//監聽if(listen(listenfd, SOMAXCONN) < 0){ERR_EXIT("listen");}//使用poll并關注pollin事件struct pollfd pfd;pfd.fd = listenfd;pfd.events = POLLIN;//儲存poll的描述符PollfdList pollfds;pollfds.push_back(pfd);int nready;struct sockaddr_in peerAddr;socklen_t peerlen;int connfd;int idlefd;//空閑描述符//循環處理while (true) {//取事件nready = poll(pollfds.data(), pollfds.size(), -1);if(nready == -1){if(errno == EINTR){continue;}ERR_EXIT("poll");}else if(nready == 0){continue;}//如果有POLLIN事件if(pollfds[0].revents & POLLIN){//接受peerlen = sizeof(peerAddr);connfd = ::accept4(listenfd, (sockaddr *)&peerAddr, &peerlen, SOCK_NONBLOCK | SOCK_CLOEXEC);//剔除空閑連接if (connfd == -1) {if (errno == EMFILE) {close(idlefd);idlefd = accept(listenfd, NULL, NULL);close(idlefd);idlefd = open("/dev/null", O_RDONLY | O_CLOEXEC);continue;}else ERR_EXIT("accept4");}//加入到監聽pfd.fd = connfd;pfd.events = POLL_IN;pfd.revents = 0;pollfds.push_back(pfd);--nready;//連接成功std::cout << "ip = " << inet_ntoa(peerAddr.sin_addr)<< " port = " << ntohs(peerAddr.sin_port) << std::endl;if (nready == 0)continue;}//std::cout << "pollfds size: " << pollfds.size() << std::endl;//std::cout << "nready fds: " << nready << std::endl;//遍歷判斷哪些套接字產生了事件for (auto it = pollfds.begin() + 1; it != pollfds.end() && nready > 0; ++it) {//如果是可讀事件if (it->revents & POLL_IN) {--nready;connfd = it->fd;char buf[1024] = {0};//讀取數據int ret = read(connfd, buf, 1024);if (ret == -1)ERR_EXIT("read");if (ret == 0) {std::cout << "client closed" << std::endl;it = pollfds.erase(it);--it;close(connfd);continue;}std::cout << buf << std::endl;//將接收的消息返回給客戶端write(connfd, buf, strlen(buf));}}}return 0;
}

2.3 echoServer_epoll.cpp

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>#include <cstdio>
#include <cstring>#include <arpa/inet.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <unistd.h>#include <signal.h>
#include <sys/epoll.h>
#include <sys/socket.h>#define ERR_EXIT(m) \do {\perror(m); \exit(EXIT_FAILURE); \} while(0)using EventList = std::vector<epoll_event>;int main()
{signal(SIGPIPE, SIG_IGN);signal(SIGCHLD, SIG_IGN);//創建一個監聽套接字(非阻塞套接字)int listenfd;listenfd = socket(PF_INET, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, IPPROTO_TCP);if(listenfd < 0){ERR_EXIT("socket");}//設置地址struct sockaddr_in srvAddr;memset(&srvAddr,0,sizeof(srvAddr));//初始化srvAddr.sin_family = AF_INET;srvAddr.sin_port = htons(8888);srvAddr.sin_addr.s_addr = htonl(INADDR_ANY);//設置地址的重復利用int on = 1;if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0){ERR_EXIT("setsockopt");}//綁定if(bind(listenfd, (sockaddr *)&srvAddr, sizeof(srvAddr)) < 0){ERR_EXIT("bind");}//監聽if(listen(listenfd, SOMAXCONN) < 0){ERR_EXIT("listen");}std::vector<int> clients;int epollfd = epoll_create(EPOLL_CLOEXEC);//使用EPOLLIN并關注EPOLLIN事件struct epoll_event event;event.data.fd = listenfd;event.events = EPOLLIN;epoll_ctl(epollfd, EPOLL_CTL_ADD, listenfd, &event);//儲存epoll的描述符EventList events(16);struct sockaddr_in peerAddr;socklen_t peerlen;int connfd;int idlefd;//空閑描述符int nready;//循環處理while (true) {//取事件nready = epoll_wait(epollfd, events.data(), static_cast<int>(events.size()), -1);if(nready == -1){if(errno == EINTR){continue;}ERR_EXIT("epoll_wait");}else if(nready == 0){continue;}if (static_cast<size_t>(nready) == events.size()) {events.resize(events.size() * 2);} for (auto e : events) {if (e.data.fd == listenfd) {peerlen = sizeof(peerAddr);connfd = ::accept4(listenfd, (sockaddr *)&peerAddr, &peerlen, SOCK_NONBLOCK | SOCK_CLOEXEC);if (connfd == -1) {if (errno == EMFILE) {close(idlefd);idlefd = accept(listenfd, NULL, NULL);close(idlefd);idlefd = open("/dev/null", O_RDONLY | O_CLOEXEC);continue;}else ERR_EXIT("accept4");}clients.push_back(connfd);event.data.fd = connfd;event.events = EPOLLIN;epoll_ctl(epollfd, EPOLL_CTL_ADD, connfd, &event);std::cout << " connection from ip = " << inet_ntoa(peerAddr.sin_addr)<< " port = " << ntohs(peerAddr.sin_port) << std::endl;}else if (e.events & EPOLLIN) {connfd = e.data.fd;char buf[1024] = {0};int ret = read(connfd, buf, 1024);if (ret == -1)ERR_EXIT("read");if (ret == 0) {std::cout << "client closed" << std::endl;event = e; epoll_ctl(epollfd, EPOLL_CTL_DEL, connfd, &event);clients.erase(std::remove(clients.begin(), clients.end(), connfd), clients.end());close(connfd);continue;}std::cout << "msg: " << buf << std::endl;write(connfd, buf, strlen(buf));}}}return 0;
}