Stream Socket server cannot handle more than 382 threads (one per connection) on Linux

Question

I am trying to write a server program that creates a process for processing several client connections that creates one thread for each connection. But the maximum number of threads created by this process never exceeds 382.

Why can't I create more threads that process a single file descriptor to communicate with a single client, while the file descriptor limit on a process is 1024 in Linux?

I am using a Kubuntu-based system on Core-i3 with 2 GB of RAM.

Here is the code for the main function.

int server_start(void)
{
listen(skid,10000);
scnt=0;
printf("Server Listening at port:%d\n",serdt.port);
for(scnt=0;scnt<1000;)
{
        sdata->cpid[scnt]=fork();
        switch(sdata->cpid[scnt])
        {
            case -1:    printf("Could not Fork\n"); break;
            case  0:    mxsubserver(scnt); exit(0);
            default:    scnt++; break;
        }
//  }
    //check for other parameters
    pause();
}
while(1);
}

A variable not declared in a function is a global variable. I have an empty handler for signal number 50 to exit pause.

() , ( ), . , fork ...

typedef struct
{
    int cln;
    int cnt;
    int fd;
    pthread_t ptid;
}service_d;

void mxsubserver(int cln)
{//cln is the child sub-server number
int ln,fd,rfp;
pthread_t ptid;
pthread_attr_t attr;
iflag=1;

sub_data = shmat(shmid,NULL,SHM_RND);

signal(SIGINT,sub_sigint);
signal(SIGPIPE,sub_sigpipe);
signal(50,SIG_DFL);
parg = malloc(sizeof(service_d));
parg->cln = cln;
cnt=0;
printf("Server Instance %d Started\n",cln);
for(cnt=0;;)
{
    if(iflag)
    {
        cnt++;
        ln = (socklen_t)sizeof(struct sockaddr_in);
        fd = accept(skid,(struct sockaddr *)&sktaddr,&ln);
        parg->fd=fd;
        parg->cnt=(cln*1000)+cnt;
        pthread_attr_init(&attr);
        pthread_create(&(parg->ptid),&attr,&service,parg);
        pthread_detach(parg->ptid);
        pthread_attr_destroy(&attr);
        sub_data->openfd[cln]=cnt;
    }
    if(cnt>=1000)
    {
        printf("Limit Reached\n");
        iflag=getppid();
        printf("Signalling Parent\n");
        kill(iflag,50);
        iflag=0;
        pause();
    }
    if(cnt==0)
    {
        free(parg);
        exit(0);
    }
}
kill(getppid(),50);
while(1);
return;
}
void sub_sigint(int sn)
{
free(parg);
shmdt(sub_data);
exit(0);
}

void sub_sigpipe(int sn)
{
cnt--;
iflag=1;
}

void* service(void *arg)
{//handle the client requests
int fd,cln,l,ol;
char im[100],*msg="This is from Server\n";
service_d *srd;

srd = (service_d*)arg;
//pthread_detach(srd->ptid);
fd = srd->fd;
cln = srd->cnt;
printf("service cln: %d f: %d\n",cln,iflag);
ol=strlen(msg);

while(1)
{
    read(fd,&l,sizeof(int)); //open to get sigpipe error if client closes
    if(read(fd,im,l)<0) break;
    im[l]='\0';
//  printf("Server %d thread %d: Got >> %s\n",srd->cln,cln,im);
    if(write(fd,&ol,sizeof(int))<0) break;
    if(write(fd,msg,ol)<0) break;;
}
close(fd);
pthread_exit("Done\n");
}

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Answer 1

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: / Linux

- 8 . 382 , , , 8x382, .. 3 .

30 pthread_attr_setstacksize. , 6000 , - libgcc_s.so.1 must be installed for pthread_cancel to work. , : apt-get install libgcc1-dbg root.