diff --git a/fbsh.cc b/fbsh.cc
index 58f0ee3..4add649 100644
--- a/fbsh.cc
+++ b/fbsh.cc
@@ -9,9 +9,27 @@
 #include <libxml/xmlmemory.h>
 #include <libxml/parser.h>
 #include <UDPTCPNetwork.h>
+#include <math.h>
 
 #include "fbsh.h"
 
+/*
+ * implementation of the function atoi and atof but with additional check for NULL pointer
+ * atoi_check will return fallback value on error
+ * atof will return NAN
+ */
+double atof_check (char *s) {
+	if (s != NULL) return (atof(s));
+	return NAN;
+}
+
+
+int atoi_check (char *s, int failnumber) {
+	if (s != NULL) return (atoi(s));
+	return failnumber;
+}
+
+
 std::string generateMD5 (char* input, int size) {
     int i;
     MD5_CTX md5;
@@ -484,10 +502,10 @@ int FBSmartHome::GetHKR(std::string ain, FBSmartHomeHKR *hkr) {
 					xmlNodePtr xmlc = xmlchild->children;
 					while(xmlc) {
 						if (!xmlStrcmp(xmlc->name, (const xmlChar *)"celsius")) {
-							hkr->temp = (atof ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1))) / 10.0;
+							hkr->temp = (atof_check((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1))) / 10.0;
 						}
 						else if (!xmlStrcmp(xmlc->name, (const xmlChar *)"offset")) {
-							hkr->offset = atoi ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
+							hkr->offset = atoi_check ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1), -999);
 						}
 
 						xmlc = xmlc->next;
@@ -499,19 +517,19 @@ int FBSmartHome::GetHKR(std::string ain, FBSmartHomeHKR *hkr) {
 					xmlNodePtr xmlc = xmlchild->children;
 					while(xmlc) {
 						if (!xmlStrcmp(xmlc->name, (const xmlChar *)"tist")) {
-							hkr->temp_cur = atof ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
+							hkr->temp_cur = atof_check ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
 							hkr->temp_cur = hkr->temp_cur / 2.0;
 						}
 						else if (!xmlStrcmp(xmlc->name, (const xmlChar *)"tsoll")) {
-							hkr->temp_set = atof ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
+							hkr->temp_set = atof_check ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
 							hkr->temp_set = hkr->temp_set / 2.0;
 						}
 						else if (!xmlStrcmp(xmlc->name, (const xmlChar *)"absenk")) {
-							hkr->temp_l = atof ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
+							hkr->temp_l = atof_check ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
 							hkr->temp_l = hkr->temp_l / 2.0;
 						}
 						else if (!xmlStrcmp(xmlc->name, (const xmlChar *)"komfort")) {
-							hkr->temp_h = atof ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
+							hkr->temp_h = atof_check ((char *) xmlNodeListGetString(xmldoc, xmlc->children, 1));
 							hkr->temp_h = hkr->temp_h / 2.0;
 						}
 
@@ -560,9 +578,9 @@ int FBSmartHome::GetHKR(std::string ain, FBSmartHomeHKR *hkr) {
 							xmlattr = xmlc->properties;
 							while (xmlattr) {
 								if (!xmlStrcmp(xmlattr->name, (const xmlChar *)"count"))
-									count = atoi((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1));
+									count = atoi_check((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1), -999);
 								else if (!xmlStrcmp(xmlattr->name, (const xmlChar *)"grid"))
-									hkr-> statsgrid = atoi((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1));
+									hkr-> statsgrid = atoi_check((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1), -999);
 								xmlattr = xmlattr->next;
 							}
 
@@ -572,7 +590,7 @@ int FBSmartHome::GetHKR(std::string ain, FBSmartHomeHKR *hkr) {
 							t = (char*)txt.c_str();
 							for (int i = 0; t != NULL && i < count; i++) {
 								if (*t == ',') t++;
-								f = atoi (t);
+								f = atoi_check (t, 0);
 								hkr->stats.push_back(f);
 								t = strchr(t, ',');
 							}
@@ -707,11 +725,11 @@ std::list<FBSmartHomeLightDefaults> *FBSmartHome::GetColorDefaults (std::string
 									FBSmartHomeLightDefaults def = { -1, -1, -1 };
 									while (xmlattr) {
 										if (!xmlStrcmp(xmlattr->name, (const xmlChar *)"hue"))
-											def.hue = atoi((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1));
+											def.hue = atoi_check((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1), 0);
 										else if (!xmlStrcmp(xmlattr->name, (const xmlChar *)"sat"))
-											def.sat = atoi((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1));
+											def.sat = atoi_check((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1), 0);
 										else if (!xmlStrcmp(xmlattr->name, (const xmlChar *)"val"))
-											def.val = atoi((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1));
+											def.val = atoi_check((char *) xmlNodeListGetString(xmldoc, xmlattr->children, 1), 0);
 										xmlattr = xmlattr->next;
 									}
 									if (def.hue != -1) lst->push_back(def);