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

1. socket搭建网络库必须用到的
2. epoll 多路复用技术用的是epoll
3. 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
4. pipe 用在进程间通讯 0是读 1是写
5. sem 信号 用在进程间通讯
6. pthread_con_t 条件变量，用于进程间通讯
7. cmake 用来编译工程

下面是服务器代码：epollserver.cpp

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include 

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
#include
#include
#include
#include
#include
#include

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