Socket Server with Multiple clients. Killing child processes - c++

Question

I have been writing a server that supposed to work with multiple clients using fork().
I am closing the sockets and exiting the child processes, but after handling all the clients I end up with tons of child processes (Have checked it with ps -ef).
Am I missing something here?
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include "sbb_socket.h"
#include "bond_container.h"
#include <iostream>
#define SBB_ANY
void do_process(int sd_current);
int main(int argc, char* argv[])
{
/*
* get the number of clients from argument
*/
long client_count = 1;
if (argc > 1 && strtol(argv[1], NULL, 10) > 0) {
client_count = strtol(argv[1], NULL, 10);
}
pid_t pid;
int sd_current;
/*
* get an internet domain socket
*/
int sd;
if ((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
perror("socket");
exit(1);
}
/*
* set up the socket structure
*/
struct sockaddr_in sock_addr;
memset(&sock_addr, 0, sizeof(sock_addr));
sock_addr.sin_family = AF_INET;
#ifdef SBB_ANY
/* set to INADDR_ANY if want server to be open to any client on any machine */
sock_addr.sin_addr.s_addr = INADDR_ANY;
#else
char hostname[128];
/*
* we'll default to this host and call a section 3 func to get this host
*/
if( gethostname(hostname,sizeof(hostname)) ){
fprintf(stderr," SBB gethostname(...) failed errno: %d\n", errno);
exit(1);
}
//printf("SBB gethostname() local hostname: \"%s\"\n", hostname);
/*
* set up socket structure for our host machine
*/
struct hostent *hp;
if ((hp = gethostbyname(hostname)) == 0) {
fprintf(stderr,"SBB gethostbyname(...) failed errno: %d exiting...\n", errno);
exit(1);
}
sock_addr.sin_addr.s_addr = ((struct in_addr *)(hp->h_addr))->s_addr;
#endif
sock_addr.sin_port = htons(PORT);
/*
* bind the socket to the port number
*/
if (bind(sd, (struct sockaddr *) &sock_addr, sizeof(sock_addr)) == -1) {
perror("bind");
exit(1);
}
/*
* advertise we are available on this socket/port
*/
if (listen(sd, 5) == -1) {
perror("listen");
exit(1);
}
while(1)
{
/*
* wait for a client to connect
*/
struct sockaddr_in sock_addr_from_client;
socklen_t addrlen = sizeof(sock_addr_from_client);
if ((sd_current = accept(sd, (struct sockaddr *) &sock_addr_from_client, &addrlen)) == -1) {
fprintf(stderr,"SBB accept(...) failed errno: %d exiting...\n", errno);
exit(1);
}
/*
* block on socket waiting for client message
*/
if ((pid = fork()) < 0) {
printf("Error on fork");
exit(1);
}
if (pid == 0) {
close(sd);
do_process(sd_current);
exit(0);
}
else {
close(sd_current);
}
}
}

Answer 1

The hanging child processes are probably zombie processes.
You could do for example following for avoiding problem:
Use waitpid() of wait() in parent process to get rid of zombies.
Use 'double fork' trick to put child processes under init process.