Sarver.c

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

#define PORTA 666
#define CONEXOES 5
#define MAXDATASIZE 2000

main() {
	char buffer[MAXDATASIZE];

	int nsocket, newsocket;
	struct sockaddr_in server_endereco;
	struct sockaddr_in endereco_cliente;
	int tam;

	if ((nsocket = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		perror("socket");
		exit(1);
	}

	server_endereco.sin_family = AF_INET;
	server_endereco.sin_port = htons(PORTA);
	server_endereco.sin_addr.s_addr = INADDR_ANY; //incorpora o IP padrão do hospedeiro

	bzero(&(server_endereco.sin_zero), 8);
	if  (bind(nsocket,  (struct  sockaddr  *)&server_endereco,  
		sizeof(struct sockaddr)) == -1) {
		perror("bind");
		exit(1);
	}

	if (listen(nsocket, CONEXOES) < 0) {
		perror("listen");
		exit(1);
	}

	while(1) {
		tam = sizeof(struct sockaddr_in);

		if ((newsocket = accept(nsocket, (struct sockaddr*) 
			&endereco_cliente,&tam)) < 0) {
			perror("accept");
			continue;
		}

		printf("Cliente conectando em %s\n", inet_ntoa(endereco_cliente.sin_addr));

		if (numbytes = recv(nsocket, buffer, MAXDATASIZE, 0) == -1) {
			perror("recv");
		}

		if (!fork()) {
			buffer[numbytes] = '\0';
			toupper(buffer);

			if (send(newsocket, buffer, strlen(buffer), 0) == -1)
				perror("send");
	
			close(newsocket);
		}

		close(newsocket);
		while(waitpid(-1, NULL, WNOHANG) > 0);
	}
}