Implementación Servidor Concurrente (C)

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
 
#define	PORT	5000
 
/* Correspondiente a la clase del 08/09/2009 */
 
typedef struct sockaddr *sad;
 
void error(char *s)
{
	perror(s);
	exit(-1);
}
 
void handler (int sig)
{
	wait(NULL);
}
 
int main ()
{
	int sock, sock1;
	struct sockaddr_in sin,sin1;
	socklen_t l;
	char buff[1024];
	int cto;
 
	signal (SIGCHLD, handler);
 
	if ((sock=socket(PF_INET, SOCK_STREAM, ))<) error("socket");
	sin.sin_family=AF_INET;
	sin.sin_port=htons(PORT);
	sin.sin_addr.s_addr=INADDR_ANY;
 
	if(bind(sock, (sad) &sin, sizeof sin) < ) error("bind");
	if(listen(sock, 5) <  ) error("hola");
 
	for (;;) {
		l= sizeof(sin1);
		if ((sock1=accept(sock, (sad) &sin, &l)) < )
			error("accept");
 
		/* sin el siguiente if, no es multiproceso */
		if (fork() == ) {
			printf("(%s, %d)\n", inet_ntoa(sin.sin_addr),
					ntohs(sin1.sin_port));
			if ((cto=read(sock1, buff, sizeof buff)) < )
				error("read");
 
			buff[cto]=;
			{ int i;
			for (i = ; i < cto; i++ ) 
				buff[i] = toupper(buff[i]);
			}
			sleep(10);
 
			if (write (sock1, buff, cto) < )
				error("write");
			close(sock1);
			exit ();
		}
		close(sock1);
	}
	return ;
}