Socket ( server client Get pid )

hi guys
now I want to change the server so that it is able to serve more customers
simultaneously. as there is a process "generic "
initially creates the server and then creates the customer (at random intervals). Each
client requests the server to process a string, and has been answered,
ends. The creation of the customers that the process continues until the generator
it receives a SIGINT signal (eg, keyboard). At which point the
generator stops generating customers, when all customers have been completed,
sends a SIGUSR1 signal to the server that runs it close. The
communication between clients and servers must be made through a single socket.
....
I wrote up here guys ... but I do not know as I continue ..
please help me

code server :

Code:

/* upperserver.c : un server per maiuscolare linee di testo */
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <ctype.h>

#define SERVER_PORT 1313
#define LINESIZE 80

void
upperlines (int in, int out)
{
  char inputline[LINESIZE];
  int len, i;

  while ((len = recv (in, inputline, LINESIZE, 0)) > 0)
    {
	    sleep(10);
      for (i = 0; i < len; i++)
	inputline[i] = toupper (inputline[i]);
      send (out, inputline, len, 0);
    }
}

int
main (unsigned argc, char **argv)
{
  int sock, client_len, fd;
  struct sockaddr_in server, client;

  /* impostazione del transport end point */
  if ((sock = socket (AF_INET, SOCK_STREAM, 0)) == -1)
    {
      perror ("chiamata alla system call socket fallita");
      exit (1);
    }

  server.sin_family = AF_INET;
  server.sin_addr.s_addr = INADDR_ANY;
  server.sin_port = htons (SERVER_PORT);

  /* binding dell'indirizzo al transport end point */
  if (bind (sock, (struct sockaddr *) &server, sizeof server) == -1)
    {
      perror ("chiamata alla system call bind fallita");
      exit (2);
    }

  listen (sock, 1);

  /* gestione delle connessioni dei client */
  while (1)
    {
      client_len = sizeof (client);
      if ((fd = accept (sock, (struct sockaddr *) &client, &client_len)) < 0)
	{
	  perror ("accepting connection");
	  exit (3);
	}
      fprintf (stderr, "Aperta connessione.\n");
      send (fd, "Benvenuto all'UpperServer!\n", 27, 0);
      upperlines (fd, fd);
      close (fd);
      fprintf (stderr, "Chiusa connessione.\n");
    }
}

********************************************************************************
code client :

#include   <stdio.h>
#include   <stdlib.h>
#include   <string.h>
#include   <ctype.h>
#include   <sys/types.h>
#include   <sys/socket.h>
#include   <netinet/in.h>

#define MAXLENGTH 80
#define SERVER_PORT 1313

main ()
{
  int sockfd;
  struct sockaddr_in server={AF_INET,htons(SERVER_PORT),INADDR_ANY};
  int i = 0, len;
  char buf[MAXLENGTH], c;

  if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
      perror("chiamata alla system call socket fallita");
      exit(1);
    }

  /* connessione al server */
  if (connect(sockfd, (struct sockaddr *) &server, sizeof server) == -1)
    {
      perror("connessione al server fallita");
      exit(2);
    }

  /* ricezione e stampa a video del messaggio di benvenuto del server */
  if (recv(sockfd, buf, 27, 0) > 0)
    {
      printf("%s", buf);
    }
  else
    {
      perror("Connessione al server interrotta");
      exit(3);
    }

  /* acquisizione della stringa da standard input */
  printf("\nDigita una stringa:");
  while ((c = getchar()) != '\n' && i < MAXLENGTH)
    buf[i++] = c;

  buf[i] = '\0';
  len = strlen(buf);

  /* invio e ricezione della stringa */
  if (send(sockfd, buf, len, 0) == -1)
    {
      perror("Errore nell'invio della stringa al server");
      exit(4);
    }

  if (recv(sockfd, buf, len, 0) > 0)
    {
      printf("%s\n", buf);
    }
  else
    {
      perror("Connessione al server interrotta");
      exit(3);
    }

  /* chiusura della connessione */
  close(sockfd);
}

thank you for help!!