网络编程--服务器编程模型

最新推荐文章于 2024-04-29 07:45:00 发布

yfk

最新推荐文章于 2024-04-29 07:45:00 发布

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分类专栏：网络编程网络编程文章标签：编程服务器网络 events struct 多线程

本文链接：https://blog.youkuaiyun.com/yfkiss/article/details/7553832

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本文通过一个简单的例子，介绍网络服务器编程模型
服务器接受客户端连接请求，回显客户端发过来的数据，发送当前时间给客户端

所有源码可打包下载：
http://download.youkuaiyun.com/detail/yfkiss/4318990

客户端请求相关代码：

        //和服务器建立连接
        if(connect(sockfd,(struct sockaddr *)&their_addr,sizeof(struct sockaddr))==-1)
        {
                perror("connect");
                exit(1);
        }

        //向服务器发送请求
        if(send(sockfd,buf,strlen(buf),0)==-1)
        {
                perror("send");
                exit(1);
        }
        memset(buf,0,sizeof(buf));

        //接受从服务器返回的信息
        if((numbytes = recv(sockfd,buf,100,0))==-1)
        {
                perror("recv");
                exit(1);
        }
        else
        {
                printf("Time: %s\n", buf);
        }

简单服务器模型

服务器进程接受连接，处理请求，然后等待下一个连接，如图：

核心代码：

        //等待连接
	while(1) 
	{
		struct sockaddr cliaddr;
		sin_size = sizeof(struct sockaddr);
		
		//接受连接
		if((new_fd = accept(sockfd, (struct sockaddr *)&cliaddr, (socklen_t*)&sin_size))==-1)
		{
			perror("accept");
			return -1;
		}

		char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];
	 	getnameinfo(&cliaddr, sizeof(cliaddr), hbuf, sizeof hbuf, sbuf, sizeof sbuf, NI_NUMERICHOST | NI_NUMERICSERV);  
		printf("Accepted connection: host=%s, port=%s\n", hbuf, sbuf);
		
		//读取客户端发来的信息
		memset(buff,0,sizeof(buff));
		if((numbytes = recv(new_fd,buff,sizeof(buff),0))==-1)
		{
			perror("recv");
			return -1;
		}	
		
		//获取系统时间
		time_t now = time(0);
		sprintf(buff, "Server Time is : %s", ctime(&now));
		
		//将从客户端接收到的信息再发回客户端
		if(send(new_fd,buff,strlen(buff),0)==-1)
		{
			perror("send");
		}
	
		//关闭连接
		close(new_fd);
	}

多进程模型

服务器进程接受连接，fork一个子进程为客户服务，然后等待下一个连接。
多进程模型适用于单个客户服务需要消耗较多的 CPU 资源，例如需要进行大规模或长时间的数据运算或文件访问。多进程模型具有较好的安全性。
如图：

核心代码：

	//等待连接
	while(1) 
	{
		struct sockaddr cliaddr;
		sin_size = sizeof(struct sockaddr);
		
		//接受连接
		if((new_fd = accept(sockfd, (struct sockaddr *)&cliaddr, (socklen_t*)&sin_size))==-1)
		{
			perror("accept");
			return -1;
		}

		char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];
	 	getnameinfo(&cliaddr, sizeof(cliaddr), hbuf, sizeof hbuf, sbuf, sizeof sbuf, NI_NUMERICHOST | NI_NUMERICSERV);  
		printf("Accepted connection: host=%s, port=%s\n", hbuf, sbuf);
	
                //fork子进程处理请求
		if(!fork())
		{
			process(new_fd);
			
			//关闭连接
			close(new_fd);
			return 0;
		}
	
	}
	close(sockfd);
}

多线程模型

和多进程模型类似，服务器进程接受连接，新建一个线程为客户服务，然后等待下一个连接
和多进程相比，由于进程消耗的资源比线程大的多，因此，在需要为较多客户端服务的时候，优先使用多线程。
如图：

代码：

void* process(void* arg)
{
	int new_fd = *(int*)arg;
	char buff[1024];
	int numbytes;
	
	//读取客户端发来的信息
	memset(buff,0,sizeof(buff));
	if((numbytes = recv(new_fd,buff,sizeof(buff),0))==-1)
	{
		perror("recv");
		return NULL;
	}
		
		
	//获取系统时间
	time_t now = time(0);
	sprintf(buff, "Server Time is : %s", ctime(&now));
	
	//将从客户端接收到的信息再发回客户端
	if(send(new_fd,buff,strlen(buff),0)==-1)
	{
		perror("send");
		return NULL;
	}
	
	close(new_fd);
        pthread_exit(NULL);
	return NULL;
}
	
int main()
{
	......
	
	//等待连接
	while(1) 
	{
		struct sockaddr cliaddr;
		sin_size = sizeof(struct sockaddr);
		
		//接受连接
		if((new_fd = accept(sockfd, (struct sockaddr *)&cliaddr, (socklen_t*)&sin_size))==-1)
		{
			perror("accept");
			return -1;
		}

		char hbuf[NI_MAXHOST], sbuf[NI_MAXSERV];
	 	getnameinfo(&cliaddr, sizeof(cliaddr), hbuf, sizeof hbuf, sbuf, sizeof sbuf, NI_NUMERICHOST | NI_NUMERICSERV);  
		printf("Accepted connection: host=%s, port=%s\n", hbuf, sbuf);
	
                //创建新线程为客户端服务
		if((pthread_create(&thread, NULL, process, (void*)(&new_fd))))
		{
			perror("pthread_create error");			
			return 0;
		}
	}
	close(sockfd);
}

事件驱动模型

多线程模型通过将连接与线程绑定的方式，较好的解决了同一时刻为多个客户提供请求的要求，但是，如果客户请求数成千上万，即使是线程，服务器也无法承受庞大的资源消耗。当然，我们可以通过使用线程池来控制线程数量，减少资源开销，但是，面对大的服务压力，池本身无法增加承载能力。
事件驱动模型使用IO复用（参考网络编程--IO模型示例），在每一个执行周期都会探测一次或一组事件，一个特定的事件会触发某个特定的响应。
相比其他模型，事件驱动模型优点是只用单线程执行，占用资源少，不消耗太多 CPU，同时能够为多客户端提供服务。缺点是程序逻辑复杂，编程复杂性较高。
如图：

核心代码：

#define MAX_EVENTS 1024 

struct myevent_s   
{   
    int fd;   
    void (*call_back)(int fd, int events, void *arg);   
    int events;   
    void *arg;   
    int status; // 1: in epoll wait list, 0 not in   
    char buff[128]; // recv data buffer  
    int len;  
    long last_active; // last active time   
};   

int g_epollFd;   
myevent_s g_Events[MAX_EVENTS+1]; // g_Events[MAX_EVENTS] is used by listen fd   
void RecvData(int fd, int events, void *arg);   
void SendData(int fd, int events, void *arg);

// set event   
void EventSet(myevent_s *ev, int fd, void (*call_back)(int, int, void*), void *arg)   
{   
    ev->fd = fd;   
    ev->call_back = call_back;   
    ev->events = 0;   
    ev->arg = arg;   
    ev->status = 0;   
    ev->len = 0;
    ev->last_active = time(NULL);   
}   

// add/mod an event to epoll   
void EventAdd(int epollFd, int events, myevent_s *ev)   
{   
    struct epoll_event epv = {0, {0}};   
    int op;   
    epv.data.ptr = ev;   
    epv.events = ev->events = events;   
    if(ev->status == 1){   
        op = EPOLL_CTL_MOD;   
    }   
    else{   
        op = EPOLL_CTL_ADD;   
        ev->status = 1;   
    }   
    if(epoll_ctl(epollFd, op, ev->fd, &epv) < 0)   
        printf("Event Add failed[fd=%d]\n", ev->fd);   
    else  
        printf("Event Add OK[fd=%d]\n", ev->fd);   
}   

// delete an event from epoll   
void EventDel(int epollFd, myevent_s *ev)   
{   
    struct epoll_event epv = {0, {0}};   
    if(ev->status != 1) return;   
    epv.data.ptr = ev;   
    ev->status = 0;   
    epoll_ctl(epollFd, EPOLL_CTL_DEL, ev->fd, &epv);   
}  
    
// accept new connections from clients   
void AcceptConn(int fd, int events, void *arg)   
{   
    struct sockaddr_in sin;   
    socklen_t len = sizeof(struct sockaddr_in);   
    int nfd, i;   
    // accept   
    if((nfd = accept(fd, (struct sockaddr*)&sin, &len)) == -1)   
    {   
        if(errno != EAGAIN && errno != EINTR)   
        {   
            printf("%s: bad accept", __func__);   
        }   
        return;   
    }   
    do  
    {   
        for(i = 0; i < MAX_EVENTS; i++)   
        {   
            if(g_Events[i].status == 0)   
            {   
                break;   
            }   
        }   
        if(i == MAX_EVENTS)   
        {   
            printf("%s:max connection limit[%d].", __func__, MAX_EVENTS);   
            break;   
        }   
        // set nonblocking   
        if(fcntl(nfd, F_SETFL, O_NONBLOCK) < 0) break;   
        // add a read event for receive data   
        EventSet(&g_Events[i], nfd, RecvData, &g_Events[i]);   
        EventAdd(g_epollFd, EPOLLIN|EPOLLET, &g_Events[i]);   
        printf("new conn[%s:%d][time:%d]\n", inet_ntoa(sin.sin_addr), ntohs(sin.sin_port), g_Events[i].last_active);   
    }while(0);   
}   

// receive data   
void RecvData(int fd, int events, void *arg)   
{   
    struct myevent_s *ev = (struct myevent_s*)arg;   
    int len;   
    // receive data   
    len = recv(fd, ev->buff, sizeof(ev->buff)-1, 0);     
    EventDel(g_epollFd, ev);   
    if(len > 0)   
    {   
        ev->len = len;   
        ev->buff[len] = '\0';   
        printf("C[%d]:%s\n", fd, ev->buff);   
        // change to send event   
        EventSet(ev, fd, SendData, ev);   
        EventAdd(g_epollFd, EPOLLOUT|EPOLLET, ev);   
    }   
    else if(len == 0)   
    {   
        close(ev->fd);   
        printf("[fd=%d] closed gracefully.\n", fd);   
    }   
    else  
    {   
        close(ev->fd);   
        printf("recv[fd=%d] error[%d]:%s\n", fd, errno, strerror(errno));   
    }   
}  
 
// send data   
void SendData(int fd, int events, void *arg)   
{   
    struct myevent_s *ev = (struct myevent_s*)arg;   
    int len;  
    
    time_t now = time(0);
	sprintf(ev->buff, "Server Time is : %s", ctime(&now)); 
    // send data   
    len = send(fd, ev->buff, strlen(ev->buff), 0);   
    ev->len = 0;   
    EventDel(g_epollFd, ev);   
    if(len > 0)   
    {   
        // change to receive event   
        EventSet(ev, fd, RecvData, ev);   
        EventAdd(g_epollFd, EPOLLIN|EPOLLET, ev);   
    }   
    else  
    {   
        close(ev->fd);   
        printf("recv[fd=%d] error[%d]\n", fd, errno);   
    }   
}   
void InitListenSocket(int epollFd, short port)   
{   
    int listenFd = socket(AF_INET, SOCK_STREAM, 0);   
    fcntl(listenFd, F_SETFL, O_NONBLOCK); // set non-blocking   
    printf("server listen fd=%d\n", listenFd);   
    EventSet(&g_Events[MAX_EVENTS], listenFd, AcceptConn, &g_Events[MAX_EVENTS]);   
    // add listen socket   
    EventAdd(epollFd, EPOLLIN|EPOLLET, &g_Events[MAX_EVENTS]);   
    // bind & listen   
    sockaddr_in sin;   
    bzero(&sin, sizeof(sin));   
    sin.sin_family = AF_INET;   
    sin.sin_addr.s_addr = INADDR_ANY;   
    sin.sin_port = htons(port);   
    bind(listenFd, (const sockaddr*)&sin, sizeof(sin));   
    listen(listenFd, 5);   
}   

int main(int argc, char **argv)   
{   
    short port = 7092; // default port   
    
    // create epoll   
    g_epollFd = epoll_create(MAX_EVENTS);   
    if(g_epollFd <= 0) printf("create epoll failed.%d\n", g_epollFd);   
    	
    // create & bind listen socket, and add to epoll, set non-blocking   
    InitListenSocket(g_epollFd, port);  
     
    // event loop   
    struct epoll_event events[MAX_EVENTS];   
    printf("server running:port[%d]\n", port); 
      
    int checkPos = 0;   
    while(1){   
        // a simple timeout check here, every time 100, better to use a mini-heap, and add timer event   
        long now = time(NULL);   
        for(int i = 0; i < 100; i++, checkPos++) // doesn't check listen fd   
        {   
            if(checkPos == MAX_EVENTS) checkPos = 0; // recycle   
            if(g_Events[checkPos].status != 1) continue;   
            long duration = now - g_Events[checkPos].last_active;   
            if(duration >= 60) // 60s timeout   
            {   
                close(g_Events[checkPos].fd);   
                printf("[fd=%d] timeout[%d--%d].\n", g_Events[checkPos].fd, g_Events[checkPos].last_active, now);   
                EventDel(g_epollFd, &g_Events[checkPos]);   
            }   
        }   
        // wait for events to happen   
        int fds = epoll_wait(g_epollFd, events, MAX_EVENTS, 1000);   
        if(fds < 0){   
            printf("epoll_wait error, exit\n");   
            break;   
        }   
        for(int i = 0; i < fds; i++){   
            myevent_s *ev = (struct myevent_s*)events[i].data.ptr;   
            if((events[i].events&EPOLLIN)&&(ev->events&EPOLLIN)) // read event   
            {   
                ev->call_back(ev->fd, events[i].events, ev->arg);   
            }   
            if((events[i].events&EPOLLOUT)&&(ev->events&EPOLLOUT)) // write event   
            {   
                ev->call_back(ev->fd, events[i].events, ev->arg);   
            }   
        }   
    }   
    // free resource   
    return 0;   
}