diff --git a/server/include/file.h b/server/include/file.h
index c414f9904..74b42498f 100644
--- a/server/include/file.h
+++ b/server/include/file.h
@@ -66,7 +66,7 @@ int file_deinit();
 char * file_print(struct node *n);
 
 /** @see node_vtable::parse */
-int file_parse(config_setting_t *cfg, struct node *n);
+int file_parse(struct node *n, config_setting_t *cfg);
 
 /** @see node_vtable::open */
 int file_open(struct node *n);
diff --git a/server/include/gtfpga.h b/server/include/gtfpga.h
index 9f3ce908e..86a49f94e 100644
--- a/server/include/gtfpga.h
+++ b/server/include/gtfpga.h
@@ -55,7 +55,7 @@ int gtfpga_init(int argc, char * argv[], struct settings *set);
 int gtfpga_deinit();
 
 /** @see node_vtable::parse */
-int gtfpga_parse(config_setting_t *cfg, struct node *n);
+int gtfpga_parse(struct node *n, config_setting_t *cfg);
 
 /** @see node_vtable::print */
 char * gtfpga_print(struct node *n);
diff --git a/server/include/ngsi.h b/server/include/ngsi.h
index 2603502a0..b41aa6d65 100644
--- a/server/include/ngsi.h
+++ b/server/include/ngsi.h
@@ -72,7 +72,7 @@ int ngsi_init(int argc, char *argv[], struct settings *set);
 int ngsi_deinit();
 
 /** @see node_vtable::parse */
-int ngsi_parse(config_setting_t *cfg, struct node *n);
+int ngsi_parse(struct node *n, config_setting_t *cfg);
 
 /** @see node_vtable::print */
 char * ngsi_print(struct node *n);
diff --git a/server/include/node.h b/server/include/node.h
index 4abc81e50..7c3de43d3 100644
--- a/server/include/node.h
+++ b/server/include/node.h
@@ -27,16 +27,6 @@
 #include "list.h"
 
 /* Helper macros for virtual node type */
-#define node_type(n)			((n)->_vt->type)
-#define node_parse(n, cfg)		((n)->_vt->parse(cfg, n))
-
-#define node_read(n, p, ps, f, c)	((n)->_vt->read(n, p, ps, f, c))
-#define node_write(n, p, ps, f, c)	((n)->_vt->write(n, p, ps, f, c))
-
-#define node_open(n)			((n)->_vt->open(n))
-#define node_close(n)			((n)->_vt->close(n))
-
-
 #define REGISTER_NODE_TYPE(type, name, fnc)				\
 __attribute__((constructor)) void __register_node_ ## fnc () {		\
 	static struct node_type t = { name, type,			\
@@ -55,6 +45,18 @@ struct node_type {
 	const char *name;
 	/** A list of all existing nodes of this type. */
 	struct list instances;
+	
+	/** Global initialization per node type.
+	 *
+	 * This callback is invoked once per node-type.
+	 *
+	 * @param argc	Number of arguments passed to the server executable (see main()).
+	 * @param argv	Array of arguments  passed to the server executable (see main()).
+	 * @param set	Global settings.
+	 * @retval 0	Success. Everything went well.
+	 * @retval <0	Error. Something went wrong.
+	 */
+	int (*init)(int argc, char *argv[], struct settings *set);
 
 	enum {
 		BSD_SOCKET,		/**< BSD Socket API */
@@ -63,26 +65,46 @@ struct node_type {
 		GTFPGA,			/**< Xilinx ML507 GTFPGA card */
 		NGSI			/**< NGSI 9/10 HTTP RESTful API (FIRWARE ContextBroker) */
 	} type;				/**< Node type */
+	/** Global de-initialization per node type.
+	 *
+	 * This callback is invoked once per node-type.
+	 *
+	 * @retval 0	Success. Everything went well.
+	 * @retval <0	Error. Something went wrong.
+	 */
+	int (*deinit)();
+	
+	/** Allocate memory for an instance of this type. 
+	 *
+	 * @return A pointer to the node-type specific private data.
+	 */
+	void * (*create)();
+	
+	/** Free memory of an instance of this type.
+	 *
+	 * @param n	A pointer to the node object.
+	 */
+	int (*destroy)(struct node *n);
 
 	/** Parse node connection details.‚
 	 *
+	 * @param n	A pointer to the node object.
 	 * @param cfg	A libconfig object pointing to the node.
-	 * @param n	A pointer to the node structure which should be parsed.
 	 * @retval 0 	Success. Everything went well.
 	 * @retval <0	Error. Something went wrong.
 	 */
-	int (*parse)(config_setting_t *cfg, struct node *n);
+	int (*parse)(struct node *n, config_setting_t *cfg);
 
 	/** Returns a string with a textual represenation of this node.
 	 *
-	 * @param n	A pointer to the node structure
+	 * @param n	A pointer to the node object.
 	 * @return	A pointer to a dynamically allocated string. Must be freed().
 	 */
 	char * (*print)(struct node *n);
 
 	/** Opens the connection to this node.
 	 *
-	 * @param n	A pointer to the node.
+	 * @param n	A pointer to the node object.
 	 * @retval 0	Success. Everything went well.
 	 * @retval <0	Error. Something went wrong.
 	 */
@@ -90,7 +112,7 @@ struct node_type {
 
 	/** Close the connection to this node.
 	 *
-	 * @param n	A pointer to the node.
+	 * @param n	A pointer to the node object.
 	 * @retval 0	Success. Everything went well.
 	 * @retval <0	Error. Something went wrong.
 	 */
@@ -104,7 +126,7 @@ struct node_type {
 	 * Indexes used to address @p m will wrap around after len messages.
 	 * Some node types might only support to receive one message at a time.
 	 *
-	 * @param n 		A pointer to the node where the messages should be sent to.
+	 * @param n		A pointer to the node object.
 	 * @param pool 		A pointer to an array of messages which should be sent.
 	 * @param poolsize 	The length of the message array.
 	 * @param first		The index of the first message which should be sent.
@@ -120,7 +142,7 @@ struct node_type {
 	 * The messages have to be stored in a circular buffer / array m.
 	 * So the indexes will wrap around after len.
 	 *
-	 * @param n		A pointer to the node where the messages should be sent to.
+	 * @param n		A pointer to the node object.
 	 * @param pool		A pointer to an array of messages which should be sent.
 	 * @param poolsize	The length of the message array.
 	 * @param first		The index of the first message which should be sent.
@@ -128,29 +150,14 @@ struct node_type {
 	 * @return		The number of messages actually sent.
 	 */
 	int (*write)(struct node *n, struct msg *pool, int poolsize, int first, int cnt);
-
-	/** Global initialization per node type.
-	 *
-	 * This callback is invoked once per node-type.
-	 *
-	 * @param argc	Number of arguments passed to the server executable (see main()).
-	 * @param argv	Array of arguments  passed to the server executable (see main()).
-	 * @param set	Global settings.
-	 * @retval 0	Success. Everything went well.
-	 * @retval <0	Error. Something went wrong.
-	 */
-	int (*init)(int argc, char *argv[], struct settings *set);
 	
-	/** Global de-initialization per node type.
+	/** Reverse source and destination of a node.
 	 *
-	 * This callback is invoked once per node-type.
+	 * This is not supported by all node types!
 	 *
-	 * @retval 0	Success. Everything went well.
-	 * @retval <0	Error. Something went wrong.
+	 * @param n		A pointer to the node object.
 	 */
-	int (*deinit)();
-
-	int refcnt;	/**< Reference counter: how many nodes are using this node-type? */
+	int (*reverse)(struct node *n);
 };
 
 /** The data structure for a node.
@@ -179,58 +186,72 @@ struct node
 	config_setting_t *cfg;	/**< A pointer to the libconfig object which instantiated this node */
 };
 
-/** Initialize node type subsystems.
+/** Initialize all registered node type subsystems.
  *
- * These routines are only called once per type (not per node instance).
- * See node_vtable::init
+ * @see node_type::init
  */
 int node_init(int argc, char *argv[], struct settings *set);
 
 /** De-initialize node type subsystems.
  *
- * These routines are only called once per type (not per node instance).
- * See node_vtable::deinit
+ * @see node_type::deinit
  */
 int node_deinit();
 
-/** Connect and bind the UDP socket of this node.
+/** Create a node by allocating dynamic memory.
  *
- * Depending on the type (vtable) of this node,
- *  a socket is opened, shmem region registred...
- *
- * @param n A pointer to the node structure
- * @retval 0 Success. Everything went well.
- * @retval <0 Error. Something went wrong.
+ * @see node_type::create
+ * @param vt A pointer to the node-type table of virtual functions.
  */
-int node_start(struct node *n);
-
-/** Return a pointer to a string which should be used to print this node */
-char * node_print(struct node *n);
-
-/** Stops a node.
- *
- * Depending on the type (vtable) of this node,
- *  a socket is closed, shmem region released...
- *
- * @param n A pointer to the node structure
- * @retval 0 Success. Everything went well.
- * @retval <0 Error. Something went wrong.
- */
-int node_stop(struct node *n);
-
-/** Reverse local and remote socket address.
- * This is usefull for the helper programs: send, receive, test
- * because they usually use the same configuration file as the
- * server and therefore the direction needs to be swapped. */
-void node_reverse(struct node *n);
-
-/** Create a node by allocating dynamic memory. */
 struct node * node_create(struct node_type *vt);
 
 /** Destroy node by freeing dynamically allocated memory.
  *
- * @param i A pointer to the interface structure.
+ * @see node_type::destroy
  */
 void node_destroy(struct node *n);
 
+/** Start operation of a node.
+ *
+ * @see node_type::open
+ */
+int node_start(struct node *n);
+
+/** Stops operation of a node.
+ *
+ * @see node_type::close
+ */
+int node_stop(struct node *n);
+
+/** Parse node connection details.
+ *
+ * @see node_type::parse
+ */
+int node_parse(struct node *n, config_setting_t *cfg);
+
+/** Return a pointer to a string which should be used to print this node
+ *
+ * @see node_type::print
+ * @param i A pointer to the interface structure.
+ */
+char * node_print(struct node *n);
+
+/** Receive multiple messages at once.
+ *
+ * @see node_type::read
+ */
+int node_read(struct node *n, struct msg *pool, int poolsize, int first, int cnt);
+
+/** Send multiple messages in a single datagram / packet.
+ *
+ * @see node_type::write
+ */
+int node_write(struct node *n, struct msg *pool, int poolsize, int first, int cnt);
+
+/** Reverse local and remote socket address.
+ *
+ * @see node_type::reverse
+ */
+int node_reverse(struct node *n);
+
 #endif /** _NODE_H_ @} */
diff --git a/server/include/opal.h b/server/include/opal.h
index 88994c8e1..dc039c27b 100644
--- a/server/include/opal.h
+++ b/server/include/opal.h
@@ -74,7 +74,7 @@ int opal_init(int argc, char *argv[], struct settings *set);
 int opal_deinit();
 
 /** @see node_vtable::parse */
-int opal_parse(config_setting_t *cfg, struct node *n);
+int opal_parse(struct node *n, config_setting_t *cfg);
 
 /** @see node_vtable::print */
 char * opal_print(struct node *n);
diff --git a/server/include/socket.h b/server/include/socket.h
index ee8cb65e7..3ee306748 100644
--- a/server/include/socket.h
+++ b/server/include/socket.h
@@ -78,7 +78,7 @@ int socket_write(struct node *n, struct msg *pool, int poolsize, int first, int
 int socket_read(struct node *n, struct msg *pool, int poolsize, int first, int cnt);
 
 /** @see node_vtable::parse */
-int socket_parse(config_setting_t *cfg, struct node *n);
+int socket_parse(struct node *n, config_setting_t *cfg);
 
 /** @see node_vtable::print */
 char * socket_print(struct node *n);
diff --git a/server/src/cfg.c b/server/src/cfg.c
index 2966c5b25..9d2a582be 100644
--- a/server/src/cfg.c
+++ b/server/src/cfg.c
@@ -18,17 +18,6 @@
 #include "path.h"
 #include "hooks.h"
 
-#include "file.h"
-#ifdef ENABLE_SOCKET
- #include "socket.h"
-#endif
-#ifdef ENABLE_GTFPGA
-  #include "gtfpga.h"
-#endif
-#ifdef ENABLE_OPAL_ASYNC
-  #include "opal.h"
-#endif
-
 int config_parse(const char *filename, config_t *cfg, struct settings *set,
 	struct list *nodes, struct list *paths)
 {
diff --git a/server/src/file.c b/server/src/file.c
index 8fe33ad5a..c0241f50b 100644
--- a/server/src/file.c
+++ b/server/src/file.c
@@ -26,6 +26,15 @@ int file_deinit()
 	return 0; /* nothing todo here */
 }
 
+int file_reverse(struct node *n)
+{
+	struct file *f = n->file;
+
+	SWAP(f->read, f->write);
+
+	return 0;
+}
+
 static char * file_format_name(const char *format, struct timespec *ts)
 {
 	struct tm tm;
@@ -69,7 +78,7 @@ static int file_parse_direction(config_setting_t *cfg, struct file *f, int d)
 	return 0;
 }
 
-int file_parse(config_setting_t *cfg, struct node *n)
+int file_parse(struct node *n, config_setting_t *cfg)
 {
 	struct file *f = alloc(sizeof(struct file));
 	
diff --git a/server/src/gtfpga.c b/server/src/gtfpga.c
index ecdcc1167..9a9d6a70c 100644
--- a/server/src/gtfpga.c
+++ b/server/src/gtfpga.c
@@ -56,7 +56,7 @@ int gtfpga_deinit()
 	return 0;
 }
 
-int gtfpga_parse(config_setting_t *cfg, struct node *n)
+int gtfpga_parse(struct node *n, config_setting_t *cfg)
 {
 	struct gtfpga *g = alloc(sizeof(struct gtfpga));
 
diff --git a/server/src/ngsi.c b/server/src/ngsi.c
index a445fdbd4..51338fc23 100644
--- a/server/src/ngsi.c
+++ b/server/src/ngsi.c
@@ -223,7 +223,7 @@ static int ngsi_parse_entity(json_t *entity, struct ngsi *i, struct msg *pool, i
 	return cnt;
 }
 
-static int ngsi_parse_mapping(config_setting_t *cfg, struct list *mapping)
+static int ngsi_parse_mapping(struct list *mapping, config_setting_t *cfg)
 {
 	if (!config_setting_is_array(cfg))
 		return -1;
@@ -423,7 +423,7 @@ int ngsi_deinit()
 	return 0;
 }
 
-int ngsi_parse(config_setting_t *cfg, struct node *n)
+int ngsi_parse(struct node *n, config_setting_t *cfg)
 {
 	struct ngsi *i = alloc(sizeof(struct ngsi));
 
@@ -452,7 +452,7 @@ int ngsi_parse(config_setting_t *cfg, struct node *n)
 	if (!cfg_mapping)
 		cerror(cfg, "Missing mapping for node '%s", n->name);
 
-	if (ngsi_parse_mapping(cfg_mapping, &i->mapping))
+	if (ngsi_parse_mapping(&i->mapping, cfg_mapping))
 		cerror(cfg_mapping, "Invalid mapping for NGSI node '%s'", n->name);
 
 	n->ngsi = i;
@@ -469,6 +469,15 @@ char * ngsi_print(struct node *n)
 		i->endpoint, i->timeout, list_length(&i->mapping));
 }
 
+int ngsi_destroy(struct node *n)
+{
+	struct ngsi *i = n->ngsi;
+	
+	list_destroy(&i->mapping);
+	
+	return 0;
+}
+
 int ngsi_open(struct node *n)
 {
 	struct ngsi *i = n->ngsi;
diff --git a/server/src/node.c b/server/src/node.c
index 8c360ebb0..cb16c041b 100644
--- a/server/src/node.c
+++ b/server/src/node.c
@@ -12,27 +12,33 @@
 #include "cfg.h"
 #include "utils.h"
 
-/* Node types */
-#include "file.h"
-#ifdef ENABLE_GTFPGA
-  #include "gtfpga.h"
-#endif
-#ifdef ENABLE_OPAL_ASYNC
-  #include "opal.h"
-#endif
-#ifdef ENABLE_SOCKET
-  #include "socket.h"
-  #include <netlink/route/qdisc.h>
-  #include <netlink/route/classifier.h>
-#endif
-#ifdef ENABLE_NGSI
-  #include "ngsi.h"
-  #include <jansson.h>
-#endif
-
 /** Vtable for virtual node sub types */
 struct list node_types = LIST_INIT(NULL);
 
+int node_parse(struct node *n, config_setting_t *cfg)
+{
+	return n->_vt->parse ? n->_vt->parse(n, cfg) : -1;	
+}
+
+int node_read(struct node *n, struct msg *p, int ps, int f, int c)
+{
+	return n->_vt->read ? n->_vt->read(n, p, ps, f, c) : -1;
+}
+
+int node_write(struct node *n, struct msg *p, int ps, int f, int c)
+{
+	return n->_vt->write ? n->_vt->write(n, p, ps, f, c) : -1;
+}
+
+int node_open(struct node *n)
+{
+	return n->_vt->open ? n->_vt->open(n) : -1;
+}	
+int node_close(struct node *n)
+{
+	return n->_vt->close ? n->_vt->close(n) : -1;
+}	
+
 int node_init(int argc, char *argv[], struct settings *set)
 { INDENT
 	list_foreach(const struct node_type *vt, &node_types) {
@@ -88,19 +94,9 @@ char * node_print(struct node *n)
 	return n->_print;
 }
 
-void node_reverse(struct node *n)
+int node_reverse(struct node *n)
 {
-	switch (node_type(n)) {
-#ifdef ENABLE_SOCKET
-		case BSD_SOCKET:
-			SWAP(n->socket->remote, n->socket->local);
-			break;
-#endif
-		case LOG_FILE:
-			SWAP(n->file->read, n->file->write);
-			break;
-		default: { }
-	}
+	return n->_vt->reverse ? n->_vt->reverse(n) : -1;
 }
 
 struct node * node_create(struct node_type *vt)
@@ -116,20 +112,8 @@ struct node * node_create(struct node_type *vt)
 
 void node_destroy(struct node *n)
 {
-	switch (node_type(n)) {
-#ifdef ENABLE_NGSI
-		case NGSI:
-			list_destroy(&n->ngsi->mapping);
-		break;
-#endif
-#ifdef ENABLE_SOCKET
-		case BSD_SOCKET:
-			rtnl_qdisc_put(n->socket->tc_qdisc);
-			rtnl_cls_put(n->socket->tc_classifier);
-			break;
-#endif
-		default: { }
-	}
+	if (n->_vt->destroy)
+		n->_vt->destroy(n);
 
 	free(n->_print);
 	free(n->socket);
diff --git a/server/src/opal.c b/server/src/opal.c
index 29c03ad77..aa875eae8 100644
--- a/server/src/opal.c
+++ b/server/src/opal.c
@@ -128,7 +128,7 @@ int opal_print_global(struct opal_global *g)
 	return 0;
 }
 
-int opal_parse(config_setting_t *cfg, struct node *n)
+int opal_parse(struct node *n, config_setting_t *cfg)
 {
 	struct opal *o = alloc(sizeof(struct opal));
 
diff --git a/server/src/socket.c b/server/src/socket.c
index 76f88de93..3ef719070 100644
--- a/server/src/socket.c
+++ b/server/src/socket.c
@@ -157,6 +157,15 @@ int socket_open(struct node *n)
 	return 0;
 }
 
+int socket_reverse(struct node *n)
+{
+	struct socket *s = n->socket;
+	
+	SWAP(s->remote, s->local);
+	
+	return 0;
+}
+
 int socket_close(struct node *n)
 {
 	struct socket *s = n->socket;
@@ -167,6 +176,16 @@ int socket_close(struct node *n)
 	return 0;
 }
 
+int socket_destroy(struct node *n)
+{
+	struct socket *s = n->socket;
+	
+	rtnl_qdisc_put(s->tc_qdisc);
+	rtnl_cls_put(s->tc_classifier);
+	
+	return 0;
+}
+
 int socket_read(struct node *n, struct msg *pool, int poolsize, int first, int cnt)
 {
 	struct socket *s = n->socket;
@@ -270,7 +289,7 @@ int socket_write(struct node *n, struct msg *pool, int poolsize, int first, int
 	return sent;
 }
 
-int socket_parse(config_setting_t *cfg, struct node *n)
+int socket_parse(struct node *n, config_setting_t *cfg)
 {
 	const char *local, *remote, *layer;
 	int ret;