32网络通信之Poll模型

Posted 2021-02-09 gd-luojialin

多路复用并发模型  -- poll

#include<poll.h>

int  poll(struct pollfd *fds,  unsigned int nfds, int timeout);

struct pollfd {

    int       fd;                //轮询的文件描述符

    short  events;         //等待的事件

    short  revents;        //实际发生的事件

}

nfds      :     fds 数组大小

timeout :     超时时间(毫秒)， 0立即返回，负数一直等待

超时返回 0， 出错返回 -1， 正常返回 > 0

 

多路复用并发模型  -- poll

事件类型

POLLIN                      有数据可读

POLLRDNORM          有普通数据可读

POLLRDBAND           有优先数据可读

POLLPRI                     有紧迫数据可读

POLLOUT                    可以写数据(不会阻塞)

POLLWRNORM           可以写普通数据

POLLWRBAND            可以写优先数据

POLLMSGSIGPOLL     消息可用

POLLER                        发生错误 (revents 可用)

POLLHUP                      文件描述符挂起 (revents 可用)

POLLNVAL                    指定的文件描述符非法(revents可用)

 

多路复用并发模型  -- poll

用法

POLLIN  =  POLLRDNORM | POLLBAND

　　监控可读事件   events = POLLIN | POLLPRI

POLLOUT = POLLWRNORM

　　监控可写事件    events = POLLOUT | POLLWRBAND

 

同时监控多个事件   events = XX1 | XX2 | XX3 | ...

若干个事件发生，返回值   revents = XX_N | XX_M | ...

 

 

多路复用并发模型  -- poll

poll 模型和 select 本质上差不多，都是fd 轮询

优点：

　　比之 select，木有最大文件描述符限制

缺点：

　　和select一样，包含大量文件描述符时，系统开销会很大

 

#include<stdio.h>
#include<unistd.h>
#include<string.h>

#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>

#include<sys/poll.h>
#include<sys/time.h>

#define SRV_PORT 0xabcd
#define CONN_MAX 10000

void PollProcss(struct  pollfd *pfds,int *plen)
{
	int i;
	int fd;
	int iRet;
	struct sockaddr_in addr;
	socklen_t addrlen = sizeof(addr);
	char szMsg[1000] = { 0 };
	char szBuff[1000] = { 0 };

	//monitor POLLIN is 1 or 0
	if (pfds[0].revents & POLLIN) 
	{
		read(0,szMsg,1000);
		for (i = 2; i < *plen; ++i)
		{
			write(pfds[i].fd, szMsg, strlen(szMsg));
		}
	}
	if (pfds[1].revents & POLLIN)
	{
		fd = accept(pfds[1].fd, (struct sockaddr*)&addr, &addrlen);
		if (fd < 0)
		{
			perror("Fail to accept!");
			return;
		}
		if (*plen == CONN_MAX)
		{
			printf("
Connect over limit
");
			write(fd, "Connect over limit", 20);
			close(fd);
		}
		else
		{
			write(fd, "Welcome", 8);
			printf("
[%d]New connect from %s[%d]
", fd, inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));

			pfds[*plen].fd = fd;
			pfds[*plen].events = POLLIN;

			(*plen)++;
		}
	}
	//TranslateMessage DispatchMessage
	for (i = 3; i < *plen; ++i)
	{
		if (pfds[i].fd.revents & POLLIN)
		{
			memset(szBuff, 0, 1000);

			iRet = read((pfds[i].fd, szBuff, 1000);
			if (iRet < 0)
			{
				perror("Fail to read!");
				break;
			}
			//Disconnect
			else if (iRet == 0)
			{
				int j;
				//Back cover front
				for (j = i; j < *plen; ++j)
				{
					pfds[j].fd = pfds[j + 1].fd;
				}
				(*plen++);
				//
				i--;

				/*  That‘s the same thing as the top
					pfds.fd=pfds[*plen-1].fd; //replace pfds[i].fd to last fd
					(*plen)--;
					i--;
				*/

			}
			//Normal processing data
			else
			{
				printf("
[%d]Recv:%s
", pfds[i].fd, szBuff);
			}

		}
	}

	return;
}

void PollServer()
{
	int fd;
	int iRet;
	struct sockaddr_in addr;
	socklen_t addrlen = sizeof(addr);

	fd = socket(PF_INET, SOCK_STREAM, 0);
	if (fd < 0)
	{
		perror("Fail to socket!");
		return;
	}

	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = htonl(INADDR_ANY);
	addr.sin_port = htons(SRV_PORT);

	iRet = bind(fd, (struct sockaddr*)&addr, addrlen);
	if (iRet)
	{
		perror("Fail to bind!");
		close(fd);
		return;
	}

	iRet = listen(fd, 100);
	if (iRet)
	{
		perror("Fail to listen!");
		close(fd);
		return;
	}

	// /////////////init pollfd
	//struct pollfd pfds[CONN_MAX];
	struct  pollfd *pfds = (struct pollfd*)malloc(CONN_MAX *sizeof(struct pollfd));
	int nfds = 0;	//fd num of array:pfds

	//monitor stdin
	pfds[0].fd = 0;
	pfds[0].events = POLLIN;
	nfds++;

	//monitor tcp server fd
	pfds[1].fd = fd;
	pfds[1].events = POLLIN;
	nfds++;
	////////////////

	printf("Start server ok..
");

	while (1)
	{
		fprintf(stderr, "Send:");
		iRet = poll(pfds, nfds, -1);
		if (iRet == 0)
		{
			//timeout
			continue;
		}
		eles if (iRet < 0)
		{
			perror("Fail to poll!");
			break;
		}
		else
		{
			PollProcss(pfds, &nfds);
		}
	}
	close(fd);
	return;
}

int main()
{
	TcpServer();
	
	return 0;
}