void SipClass::registerField(char * buf, uint8_t *ip){
	strcpy(buf, "REGISTER SIP:");
	for(uint8_t i = 0;i<3;i++){
		char *c = (char *)calloc(3, sizeof(char));
		itoa (ip[i], c, 10);
		strcat(buf, c);
		free(c);
		strcat(buf, ".");
	}
	char *c = (char *)calloc(3, sizeof(char));
	itoa (ip[4], c, 10);
	strcat(buf, c);
	free(c);
	strcat(buf, " SIP/2.0\n");
}