Commit 34595fa1 authored by Dr. Daniel Diaz Sánchez's avatar Dr. Daniel Diaz Sánchez
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parent 0d839bec
/* smart-select.c
*
* Copyright (c) 2000 Sean Walton and Macmillan Publishers. Use may be in
* whole or in part in accordance to the General Public License (GPL).
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*****************************************************************************/
/*** smart-select.c ***/
/*** ***/
/*** The smart select combines preforking with the select() call to keep ***/
/*** the select descriptor arrays small. ***/
/*****************************************************************************/
#include <stdio.h>
#include <sys/socket.h>
#include <resolv.h>
#include <unistd.h>
#include <signal.h>
#include <sys/time.h>
#define MAXPROCESSES 5
#define MAXCONNECTIONS 2
int NumChildren=0;
/*---------------------------------------------------------------------*/
/*--- sig_child - SIGCHLD ---*/
/*---------------------------------------------------------------------*/
void sig_child(int signum)
{
wait(0);
NumChildren--;
}
/*---------------------------------------------------------------------*/
/*--- servlet - each servlet accepts a connection and keeps track ---*/
/*--- of it using a select() statement. ---*/
/*---------------------------------------------------------------------*/
void servlet(int server)
{ fd_set set, set_all;
int maxfd = server;
int ceiling=0;
int i;
FD_ZERO(&set);
FD_ZERO(&set_all);
FD_SET(server, &set_all);
for (;;) {
struct timeval timeout={40,0}; /* 40 seconds */
set = set_all;
/*---Wait for some action---*/
if ( select(maxfd+1, &set, 0, 0, &timeout) > 0 ) {
/*---If new connection, connect and add to list---*/
for ( i = 0; i < maxfd+1; i++ ) {
if ( FD_ISSET(i, &set) ) {
if ( i == server ) {
if ( ceiling < MAXCONNECTIONS ) {
int client = accept(server, 0, 0);
if ( maxfd < client )
maxfd = client;
FD_SET(client, &set_all);
ceiling++;
printf("select process #%d: %d connected\n", getpid(), ceiling);
}
}
else {
char buffer[1024];
int bytes;
bytes = recv(i, buffer, sizeof(buffer), 0);
write(0, buffer, bytes);
if ( bytes == 0 ) {
close(i);
FD_CLR(i, &set_all);
ceiling--;
printf("select process #%d: %d connected\n",
getpid(), ceiling);
}
else /* process the request */
send(i, buffer, bytes, 0);
}
}
}
}
}
exit(0);
}
/*---------------------------------------------------------------------*/
/*--- main - set up server and maintain the number of living servlets--*/
/*---------------------------------------------------------------------*/
int main(int count, char *strings[])
{ int sd;
struct sockaddr_in addr;
struct sigaction act;
if ( count != 2 )
{
printf("usage: %s <port>\n", strings[0]);
exit(0);
}
bzero(&act, sizeof(act));
act.sa_handler = sig_child;
act.sa_flags = SA_NOCLDSTOP | SA_RESTART;
if ( sigaction(SIGCHLD, &act, 0) != 0 )
perror("sigaction()");
sd = socket(PF_INET, SOCK_STREAM, 0);
bzero(&addr, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(atoi(strings[1]));
addr.sin_addr.s_addr = INADDR_ANY;
if ( bind(sd, (struct sockaddr *)&addr, sizeof(addr)) == 0 )
{
listen(sd, 15);
for (;;)
{
if ( NumChildren < MAXPROCESSES )
{ int pid;
if ( (pid = fork()) == 0 )
servlet(sd);
else if ( pid > 0 )
NumChildren++;
else
perror("fork()");
}
else
sleep(1);
}
}
else
perror("bind()");
return 0;
}
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