epoll实现简易聊天小程序

前言

前几天博客托管平台被墙了，正好碰上阿里云学生计划送了7个月的云服务器，把博客部署完想着正好能用来学学网络编程

代码

服务器端

#include <iostream>
#include <map>
#include <sys/epoll.h>	// epoll_create
#include <sys/socket.h>	
#include <unistd.h>	
#include <netinet/in.h>	
#include <stdio.h>	// perror
#include <string>

// 最大连接数
const int MAX_CONN = 1024;

// 客户端信息
struct Client
{
	int sockfd;
	std::string name;
};

int main()
{
	// 创建监听socket
	int sockfd = socket(AF_INET, SOCK_STREAM, 0);
	if (sockfd < 0)
	{
		perror("socket create error!\n");
		return -1;
	}

	// 绑定本地IP和端口
	struct sockaddr_in addr;	// <netinet/in.h>
	addr.sin_family = AF_INET;	// IPv4
	addr.sin_addr.s_addr = htonl(INADDR_ANY);	// 绑定本地所有IP
	addr.sin_port = htons(9999);

	int ret = bind(sockfd, (struct sockaddr *)&addr, sizeof(addr));
	if (ret < 0)	
	{
		perror("bind error!\n");
		return -1;
	}

	// 监听客户端连接
	ret = listen(sockfd, 1024);
	if (ret < 0)
	{
		perror("listen error!\n");
		return -1;
	}

	// 创建epoll实例
	int epld = epoll_create(1);	// 参数需要大于0
	if (epld < 0)
	{
		perror("epoll create error!\n");
		return -1;
	}

	// 将监听的socket加入epoll
	struct epoll_event ev;
	ev.events = EPOLLIN;	// 读事件
	ev.data.fd = sockfd;	

	ret = epoll_ctl(epld, EPOLL_CTL_ADD, sockfd, &ev);
	if (ret < 0)
	{
		perror("epoll_ctl error!\n");
		return -1;
	}

	// 保存客户端信息
	std::map<int, Client> clients;

	// 循环监听客户端
	while (1)
	{
		struct epoll_event evs[MAX_CONN];
		int n = epoll_wait(epld, evs, MAX_CONN, -1);	// 阻塞，返回有操作的客户端的数量
		if (n < 0)
		{
			perror("epoll_wait error!\n");
			break;
		}

		for (int i = 0; i < n; ++i)
		{
			int fd = evs[i].data.fd;
			// 监听的fd收到消息
			if (fd == sockfd)
			{
				struct sockaddr_in client_addr;
				socklen_t client_addr_len = sizeof(client_addr);
				int client_sockfd = accept(sockfd, (struct sockaddr *) & client_addr, &client_addr_len);
				if (client_sockfd < 0)
				{
					perror("accept error!\n");
					continue;
				}

				// 将客户端socket加入epoll
				struct epoll_event ev_client;
				ev_client.events = EPOLLIN;	// 读事件, 检测客户端消息
				ev_client.data.fd = client_sockfd;
				ret = epoll_ctl(epld, EPOLL_CTL_ADD, client_sockfd, &ev_client);
				if (ret < 0)
				{
					perror("client_epoll_ctl error!\n");
					break;
				}
				std::cout << client_addr.sin_addr.s_addr << "has entered~" << std::endl;

				// 保存该客户端的信息
				Client client;
				client.sockfd = client_sockfd;
				client.name = "";
				clients[client_sockfd] = client;
			}
			else  // 监听到客户端消息
			{
				char buffer[1024];
				int n = read(fd, buffer, 1024);
				if (n < 0)
				{
					std::cout << "消息接收错误!" << std::endl;
					break;
				}
				else if (0 == n)	// 客户端断开连接
				{
					// 清除客户端信息
					close(fd);
					epoll_ctl(epld, EPOLL_CTL_DEL, fd, 0);
					clients.erase(fd);
				}
				else
				{
					// char数组转化为string
					std::string msg(buffer, n);
					// 若客户端name为空，则消息是该客户端的用户名
					if (clients[fd].name == "")
					{
						clients[fd].name = msg;
					}
					// 否则是聊天消息
					else
					{
						std::string name = clients[fd].name;
						// 将消息发送给其他所有客户端
						for (auto &c : clients)
						{
							if (c.first != fd)
							{
								write(c.first, ('[' + name + ']' + ": " + msg).c_str(), msg.size() + name.size() + 4);
							}
						}
					}
				}
			}
		}
	}

	// 关闭epoll实例
	close(epld);
	close(sockfd);
}

客户端

#include <Windows.h>
#include <stdio.h>
#include <iostream>
#include <WinSock2.h>
#include <WS2tcpip.h>
#pragma comment(lib,"Ws2_32.lib")   // link with Ws2_32.lib

#define BUF_SIZE 1024
char szMsg[BUF_SIZE];

unsigned SendMsg(void *arg) // 固定写法，接收任何消息
{
    SOCKET sock = *((SOCKET *)arg);

    while (1)
    {
        scanf("%s", szMsg);
        if (!strcmp(szMsg, "QUIT\n") || !strcmp(szMsg, "quit\n"))
        {
            closesocket(sock);
            exit(0);
        }

        send(sock, szMsg, strlen(szMsg), 0);
    }

    return 0;
}

unsigned RecvMsg(void* arg)
{
    SOCKET sock = *((SOCKET*)arg);

    char msg[BUF_SIZE];
    while (1)
    {
        int len = recv(sock, msg, sizeof(msg) - 1, 0);    // 字符串结束有一个'\0'所以减一
        if (len == -1)  // 服务器崩溃
        {
            return -1;
        }
        msg[len] = '\0';
        printf("%s\n", msg);
    }

    return 0;
}

int main()
{
	// 初始化socket环境
    WORD wVersionRequested;
    WSADATA wsaData;
    int err;

    wVersionRequested = MAKEWORD(2, 2);

    err = WSAStartup(wVersionRequested, &wsaData);
    if (err != 0) {
        /* Tell the user that we could not find a usable */
        /* WinSock DLL.                                  */
        return -1;
    }

    if (LOBYTE(wsaData.wVersion) != 2 ||
        HIBYTE(wsaData.wVersion) != 2) {
        WSACleanup();
        return -1;
    }
    // 建立windows socket环境

    // 创建socket
    SOCKET hSock;
    hSock = socket(AF_INET, SOCK_STREAM, 0);

    // 绑定端口
    SOCKADDR_IN servAdr;
    memset(&servAdr, 0, sizeof(SOCKADDR_IN));
    servAdr.sin_family = AF_INET;
    servAdr.sin_port = htons(9999);
    inet_pton(AF_INET, "47.115.204.216", &servAdr.sin_addr);

    // 连接服务器
    if (connect(hSock, (SOCKADDR*)&servAdr, sizeof(servAdr)) == SOCKET_ERROR)
    {
        printf("connect error: %d\n", GetLastError());
        return -1;
    }
    else
    {
        printf("欢迎来到聊天室，请输入您的用户名: ");
    }

    // 循环发消息
    HANDLE hSendHandle = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)SendMsg, (void *)&hSock, 0, NULL);

    // 循环收消息
    HANDLE hReceiveHand = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)RecvMsg, (void*)&hSock, 0, NULL);

    // 等待两个线程结束
    WaitForSingleObject(hSendHandle, INFINITE);
    WaitForSingleObject(hReceiveHand, INFINITE);

    closesocket(hSock);
    WSACleanup();
}

测试

服务器运行服务端程序，多台电脑运行客户端程序即可实现简易的收发消息

注：这里演示用的本机