Subj : Re: multi-threaded server, pthreads & sleep
To   : comp.unix.programmer,comp.programming.threads
From : parahat
Date : Wed Mar 16 2005 03:48 pm

"David Schwartz" <davids@webmaster.com> wrote in message news:<d1a293$u9g$1@nntp.webmaster.com>...
> "Parahat Melayev" <parahat@gmail.com> wrote in message 
> news:5bb6e2ec.0503161125.5d63e85f@posting.google.com...
> 
> > yes I programmed using select firstly, actually. but it is not doing
> > what it is supposed to do, when I connect 1000 client at once.
> 
>     You're going to have to get more sophisticated if you want to handle 
> more than a few hundred concurrent connections. You'll at minimum need to 
> use 'poll' instead of 'select'. You may need to raise resource limits also. 
> It's hard to know exactly what your issue is because "it is not doing what 
> it is supposed to do" is a very vague description of the problem.
> 
>     DS

Here is simple server code using epoll. but I am again facing some problems here.

- I can recv from events[i].data.fd but I can't send any data over
events[i].data.fd

- When I make multiple connections at once (say 100) I get segmentation
fault...


-------- epollserver.c ------------

#include <pthread.h>
#include <stdio.h>
#include <sys/timeb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/epoll.h>
#include <netinet/in.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#include <errno.h>

#define MAX_CLIENT 101
#define PORT 3355
#define DEBUG

int listenfd;

void nonblock(int sockfd)
{
	int opts;
	opts = fcntl(sockfd, F_GETFL);
	if(opts < 0)
	{
		perror("fcntl(F_GETFL)\n");
		exit(1);
	}
	opts = (opts | O_NONBLOCK);
	if(fcntl(sockfd, F_SETFL, opts) < 0) 
	{
		perror("fcntl(F_SETFL)\n");
		exit(1);
	}
}


int main()
{
	int epfd;
	struct epoll_event *events;
	struct epoll_event ev;
	
	struct sockaddr_in srv;
	int clifd;
	int i;
	int n;
	int res;
	char buffer[1024];
	
	if( (listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
	{
		perror("sockfd\n");
		exit(1);
	}

	bzero(&srv, sizeof(srv));
	srv.sin_family = AF_INET;
	srv.sin_addr.s_addr = INADDR_ANY;
	srv.sin_port = htons(PORT);

	if( bind(listenfd, (struct sockaddr *) &srv, sizeof(srv)) < 0)
	{
		perror("bind\n");
		exit(1);
	}
	
	listen(listenfd, 1024);

	epfd = epoll_create(MAX_CLIENT);
	if(!epfd)
	{
		perror("epoll_create\n");
		exit(1);
	}
	ev.events = EPOLLIN | EPOLLERR | EPOLLHUP;
	ev.data.fd = listenfd;
	if(epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &ev) < 0)
	{
		perror("epoll_ctl, adding listenfd\n");
		exit(1);
	}

	for( ; ; )
	{
		res = epoll_wait(epfd, events, MAX_CLIENT, 0);
		for(i = 0; i < res; i++)
		{
			if(events[i].data.fd == listenfd)
			{
				clifd = accept(listenfd, NULL, NULL);
				if(clifd > 0)
				{
					nonblock(clifd);
					ev.events = EPOLLIN | EPOLLET;
					ev.data.fd = clifd;
					if(epoll_ctl(epfd, EPOLL_CTL_ADD, clifd, &ev) < 0)
					{
						perror("epoll_ctl ADD\n");
						exit(1);
					}
				}
			}
			else {
				n = recv(events[i].data.fd, buffer, 1023, 0);
				if(n == 0)
				{
#ifdef DEBUG
					printf("%d closed connection\n", events[i].data.fd);
					epoll_ctl(epfd, EPOLL_CTL_DEL, events[i].data.fd, NULL);
#endif
				}
				else if(n < 0)
				{
#ifdef DEBUG
					printf("%d error occured, errno: %d\n",
							events[i].data.fd, errno);
#endif
				}
				else {
#ifdef DEBUG
					printf("%d data received: %s\n", 
							events[i].data.fd, buffer);
					bzero(&buffer, strlen(buffer));
#endif
					send(events[i].data.fd, buffer, strlen(buffer), 0);
				}
			}
		}
	}
	
	return 0;
}

.