Linux----网络编程（IO复用之poll系统调用函数）

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本文详细介绍了一个使用Poll机制实现的网络编程示例，包括服务器端和客户端的代码实现。服务器端通过Poll函数监听多个套接字的活动状态，当有客户端连接请求或数据到达时，能够及时响应并进行数据收发处理。

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服务器端ser_poll.c

#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <assert.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/select.h>
#include <poll.h>

//宏定义结构体大小
#define MAXFD 10 

//io_poll
//初始化描述符大小
void fds_init(struct pollfd fds[])
{
	int i = 0;
	for(; i<MAXFD; i++)
	{
		fds[i].fd = -1;
		fds[i].events = 0;
	}
}

//遍历结构体，若没有存放描述符，则将新的描述符添加到结构体中
void fds_add(struct pollfd fds[], int fd)
{
	int i = 0;
	for(; i<MAXFD; i++)
	{
		if(fds[i] == -1)
		{
			fds[i].fd = fd;
			fds[i].events = POLLIN;
			//存放完成即返回，防止遍历整个数组
			return;  
		}
	}
}

//删除结构体中与fd相等的描述符
void fds_del(struct pollfd fds[], int fd)
{
	int i = 0;
	for(; i<MAXFD; i++)
	{
		if(fds[i].fd == fd)
		{
			fds[i].fd = -1;
			fds[i].events = 0;
			return;
		}
	}
}

int main()
{
	//定义套接字
	int sockfd = socket(AF_INET, SOCK_STREAM, 0); 
	assert(socket != NULL);

	//定义协议族，端口号及IP地址
	struct sockaddr_in saddr, caddr;
	memset(&saddr, 0, sizeof(saddr));
	saddr.sin_family = AF_INET;
	saddr.sin_port = htons(6000);
	saddr.sin_addr.s_addr = inet_addr("127.0.0.1");

	//命名套接字
	int res = bind(sockfd, (struct sockaddr*)&saddr, sizeof(saddr));
	assert(res != -1);

	//监听套接字
	listen(sockfd, 5);

	//定义结构体存放描述符
	struct pollfd fds[MAXFD];
	//初始化结构体
	fds_init(fds);
	//将套接字放入结构体中
	fds_add(fds, sockfd);

	while(1)
	{
		int n_ready = poll(fds, MAXFD, 3000);
		if(n_ready == -1)
		{
			printf("poll error\n");
			continue;
		}
		if(n_ready == 0)
		{
			printf("time out\n");
		}

		int i = 0;
		for(; i<MAXFD; i++)
		{
			if(fds[i].fd == -1)
			{
				continue;
			}
			if(fds[i].revents & POLLIN)
			{
				if(fds[i].fd == sockfd)
				{
					int len = sizeof(caddr);
					int c = accept(sockfd, (struct sockaddr*)&caddr, &len);

					if(c < 0)
					{
						continue;
					}
					printf("accept = %d\n",c);
					fds_add(fds, c);
				}
				else
				{
					//普通描述符用recv()
					char buff[128] = {0};
					int num = recv(fds[i].fd, buff, 127, 0);
					if(num <= 0)
					{
						close(fds[i].fd);
						fds_del(fds, fds[i].fd);
						printf("one client over!\n");
					}
					else
					{
						printf("recv(%d) = %s\n",fds[i].fd, buff);
						send(fds[i].fd, "ok", 2, 0);
					}
				}
			}
		}
	}

}

客户端cli_poll.c

#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <assert.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main()
{
	//定义套接字
	int sockfd = socket(AF_INET, SOCK_STREAM, 0); 
	assert(socket != NULL);

	//定义协议族，端口号及IP地址
	struct sockaddr_in saddr, caddr;
	memset(&saddr, 0, sizeof(saddr));
	saddr.sin_family = AF_INET;
	saddr.sin_port = htons(6000);
	saddr.sin_addr.s_addr = inet_addr("127.0.0.1");

	//命名套接字
	int res = bind(sockfd, (struct sockaddr*)&saddr, sizeof(saddr));
	assert(res != -1);

	while(1)
	{
		char buff[128] = {0};
		printf("input:\n");
		fgets(buff, 128, stdin);

		if(strnmp(buff, "end", 3) == 0)
		{
			break;
		}
		send(sockfd, buff, strlen(buff), 0);
		memset(buff, 0, 128);
		recv(sockfd, buff, 127, 0);//127表示接收数据的大小
		printf("buff = %s\n", buff);
	}
	close(sockfd);
	exit(0);
}

运行结果：