linux实现基础网络库（socket,epoll,pthread,cmake,pipe, sem,codition,）
面试时经常会问到网络库，好久没看过这块知识了，实现一下，用到了一下一些知识点
- socket搭建网络库必须用到的
- epoll 多路复用技术用的是epoll
- pthread 服务器用到了多线程，主线程启动服务器，子线程处理来自各个连接的数据
- pipe 用在进程间通讯 0是读 1是写
- sem 信号 用在进程间通讯
- pthread_con_t 条件变量，用于进程间通讯
- cmake 用来编译工程
下面是服务器代码：epollserver.cpp
#include<stdio.h>
#include<iostream>
#include<cstring>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<fcntl.h>
#include<sys/epoll.h>
#include<errno.h>
#include<pthread.h>
#include <semaphore.h>using namespace std;
typedef struct sockaddr_in sockaddr_in;sem_t sem; // 信号
pthread_cond_t cond; // 条件变量
pthread_mutex_t mutex; // 互斥锁int pipeHandle[2]; // 管道 0读端， 1写端void set_non_blocking(int sock)
{int flag;flag = fcntl(sock, F_GETFL);if (flag < 0) {cout << "error fcntl(sock, GETFL)! " << endl;return;}flag |= O_NONBLOCK;if (fcntl(sock, F_SETFL, flag) < 0) {cout << "error fcntl(sock, F_SETFL, opts)! " << endl;return;}
}void* voteAction(void* data) {while (1){pthread_cond_wait(&cond, &mutex); // 无条件等待，与互斥锁配合防止多个线程同时调用pthread_t senderId;read(pipeHandle[0], &senderId, sizeof(senderId));cout << "vote action: people " << senderId << " vote action happen, please call 110" << endl;write(pipeHandle[1], &senderId, sizeof(senderId));sem_post(&sem);}return NULL;
}void* policeCenter(void* data)
{while (1) {sem_wait(&sem);pthread_t senderId;read(pipeHandle[0], &senderId, sizeof(senderId));cout << "110 center recevice people" << senderId << " notify vote event happened" << endl;}return NULL;
}struct my_params {int main_listenfd;int con_fd;int sock_event;int epoll_fd;
};
void* recvfromclient(void* args)
{// cout << "thread pod = " << gettid() << endl;struct my_params* params;params = (struct my_params*)args;int listenfd = (*params).main_listenfd;int co_fd = (*params).con_fd;int epfd = (*params).epoll_fd;int events = (*params).sock_event;struct epoll_event ev;int sockfd;int socklen = sizeof(struct sockaddr_in);struct sockaddr_in client_addr;char buffer[1024];if (co_fd == listenfd){cout << "accept connection, fd is " << listenfd << endl;int connfd = accept(listenfd, (struct sockaddr*)&client_addr, (socklen_t*)&socklen);if (connfd < 0){cout << "connect fd < 0" << endl;pthread_exit(NULL);return NULL;}set_non_blocking(connfd);char* str = inet_ntoa(client_addr.sin_addr);cout << "connect from " << str << endl;ev.data.fd = connfd;ev.events = EPOLLIN | EPOLLET;epoll_ctl(epfd, EPOLL_CTL_ADD, connfd, &ev);}else if (events & EPOLLIN){sockfd = co_fd;if (sockfd < 0){cout << "epoll in sockfd < 0" << endl;pthread_exit(NULL);return NULL;}memset(buffer, 0, sizeof(buffer));int ret = recv(sockfd, buffer, sizeof(buffer), 0);if (ret < 0){cout << "recv error" << endl;}else if (ret == 0) // 对端主动关闭连接是可读事件，需要处理发送改过来的FIN包,对应的是read返回0{close(sockfd);sockfd = -1;cout << inet_ntoa(client_addr.sin_addr) << "closed" << endl;return NULL;}if (string(buffer) == "exit"){cout << inet_ntoa(client_addr.sin_addr) << " closed connect" << endl;close(sockfd);sockfd = -1;return NULL;}if (string(buffer) == "vote") // 报警{pthread_t pid = gettid();write(pipeHandle[1], &pid, sizeof(pid));pthread_cond_signal(&cond); // 唤醒条件变量}cout << "receive :" << buffer << endl;ev.data.fd = sockfd;ev.events = EPOLLOUT | EPOLLET;epoll_ctl(epfd, EPOLL_CTL_MOD, sockfd, &ev);}else if (events & EPOLLOUT){sockfd = co_fd;strcpy(buffer, "ok");int ret = send(sockfd, buffer, strlen(buffer), 0);if (ret <= 0){cout << "send error" << endl;pthread_exit(NULL);return NULL;}cout << "send: " << buffer << endl;ev.data.fd = sockfd;ev.events = EPOLLIN | EPOLLET;epoll_ctl(epfd, EPOLL_CTL_MOD, sockfd, &ev);}pthread_exit(NULL);return NULL;
}int main()
{int listenfd = socket(AF_INET, SOCK_STREAM, 0); // AF_INET 协议族，ipv4协议 SOCK_STREAM tcp链接，提供序列化的，可靠的，双向连接的字节流， 第三个参数是指定协议，0自动选择type类型对应的默认协议if (listenfd == -1){cout << "socket create fail" << endl;return -1;}set_non_blocking(listenfd);struct epoll_event ev, events[20]; // ev用于注册事件，数组用于回传要处理的事件int epfd = epoll_create(256);ev.data.fd = listenfd;ev.events = EPOLLIN | EPOLLET;epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev);struct sockaddr_in serveraddr; //sockaddr_in 分别将端口和地址存储在两个结构体中memset(&serveraddr, 0, sizeof(serveraddr));serveraddr.sin_family = AF_INET;serveraddr.sin_port = htons(8000);serveraddr.sin_addr.s_addr = INADDR_ANY;if (bind(listenfd, (struct sockaddr*)&serveraddr, sizeof(serveraddr)) != 0){cout << "bind error" << endl;return -1;}if (listen(listenfd, 5) != 0){cout << "Listen error" << endl;close(listenfd);return -1;}pthread_t voteThread;int res = pthread_create(&voteThread, NULL, voteAction, NULL); // 创建一个报警线程if (res < 0){cout << "crete vote thread fail" << endl;close(listenfd);return -1;}pthread_cond_init(&cond, NULL); // 动态创建条件变量pthread_mutex_init(&mutex, NULL); // 动态创建互斥锁pthread_t policeThread;res = pthread_create(&policeThread, NULL, policeCenter, NULL);if (res < 0){cout << "crete police center thread fail" << endl;close(listenfd);return -1;}sem_init(&sem, 1, 0); // 信号量res = pipe(pipeHandle); // 管道if (res < 0){cout << "create pipe fail" << endl;close(listenfd);return -1;}cout << "*******************************welcome connect to server******************************" << endl;while (1){int nfds = epoll_wait(epfd, events, 20, 1000);if (nfds > 0){for (int i = 0; i < nfds; i++){struct my_params param;param.main_listenfd = listenfd;param.con_fd = events[i].data.fd;param.sock_event = events[i].events;param.epoll_fd = epfd;pthread_t thread;res = pthread_create(&thread, NULL, recvfromclient, (void*)¶m);if (res < 0){cout << "thread create fail" << endl;continue;}res = pthread_detach(thread); // 线程分离状态，该线程结束后，其退出状态不由其他线程获取，而字何解自己自动释放清理pcb的残留资源（进程没有该机制）if (res < 0){cout << "thread deatch fail" << endl;}}}}pthread_join(voteThread, NULL);pthread_join(policeThread, NULL);close(listenfd);return 0;
}
以下是服务器的编译文件：CMakeLists.txt
cmake_minimum_required(VERSION 3.16.3)
project(epollserver LANGUAGES CXX)link_libraries(pthread)
add_executable(server epollserver.cpp)
以上文件都是服务器端的代码，需要放在同一个目录下
以下是客户端代码：epollclient.cpp
#include<iostream>
#include<unistd.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<cstring>using namespace std;int main()
{int sockfd = socket(AF_INET, SOCK_STREAM, 0);if (sockfd <= 0){cout << "socket error";return -1;}struct sockaddr_in remote_addr;memset(&remote_addr, 0, sizeof(remote_addr));remote_addr.sin_family = AF_INET;remote_addr.sin_addr.s_addr = inet_addr("127.0.0.1");remote_addr.sin_port = htons(8000);if (connect(sockfd, (struct sockaddr*)&remote_addr, sizeof(struct sockaddr)) < 0){cout << "connect eror";return -1;}cout << "connected to server" << endl;char buffer[1024];while (1){memset(buffer, 0, sizeof(buffer));cout << "please enter message:";cin >> buffer;int len = send(sockfd, buffer, strlen(buffer), 0);if (len <= 0){cout << "send error" << endl;break;}if (string(buffer) == "exit"){cout << "good bye" << endl;break;}memset(buffer, 0, sizeof(buffer));len = recv(sockfd, buffer, 256, 0);if (len > 0){buffer[len] = '\0';cout << "Received:" << buffer << endl;}}close(sockfd);return 0;
}
以下是客户端的编译文件：CMakeLists.txt
cmake_minimum_required(VERSION 3.16.3)
project(epollclient)add_executable(client epollclient.cpp)如果不会使用Cmake 可以直接使用命令
客户端命令编译：g++ epollclient.cpp -o client -lpthread
服务器命令编译：g++ epollserver.cpp -o server -lpthread