int server_reliable_conn(int server_sock, struct sockaddr_in* server_addr){
	int control;
	char *buff = calloc(MAXLEN, sizeof(char));
	socklen_t addr_len = sizeof(*server_addr);

	//in attesa di ricevere SYN
	control = recvfrom(server_sock, buff, MAXLEN, 0, (struct sockaddr *)server_addr, &addr_len);
	if (control < 0) {
		printf("SERVER: connection failed\n");
		exit(-1);
	}
	if (strncmp(buff, SYN, strlen(SYN)) != 0) {
		printf("SERVER: connection failed(SYN)\n");
		exit(-1);
	}

	//invio del SYNACK
	control = sendto(server_sock, SYNACK, strlen(SYNACK), 0, (struct sockaddr *)server_addr, addr_len);
	if (control < 0) {
		printf("SERVER: connection failed\n");
		exit(-1);
	}

	//in attesa del ACK_SYNACK
	memset(buff, 0, sizeof(buff));
	control = recvfrom(server_sock, buff, MAXLEN, 0, (struct sockaddr *)server_addr, &addr_len);
	if (control < 0) {
		printf("SERVER: connection failed\n");
		exit(-1);
	}
	if (strncmp(buff, ACK_SYNACK, strlen(ACK_SYNACK)) != 0) {
		printf("SERVER: connection failed(ACK_SYNACK)\n");
		exit(-1);
	}

	printf("SERVER: connection established\n");
	return(1);
}