diff --git a/server/include/msg.h b/server/include/msg.h
index e6d6a9215..8fbac2686 100644
--- a/server/include/msg.h
+++ b/server/include/msg.h
@@ -14,61 +14,34 @@
 #include "config.h"
 #include "node.h"
 
-#if PROTOCOL == 0
-/** The format of a message (OPAL-RT example format).
- *
- * This struct defines the format of a message (protocol version 0).
- * Its declared as "packed" because it represents the "on wire" data.
- */
-struct msg
-{
-	/** Sender device ID */
-	uint16_t device;
-	/** Message ID */
-	uint32_t sequence;
-	/** Message length (data only) */
-	uint16_t length;
-	/** Message data */
-	double data[MAX_VALUES];
-} __attribute__((packed));
-#elif PROTOCOL == 1
-/** Next generation message format for RTDS integration.
- *
- * This struct defines the format of a message (protocol version 1).
- * Its declared as "packed" because it represents the "on wire" data.
- */
-struct msg
-{
-	struct
-	{
-		/** Protocol version */
-		unsigned version : 4;
-		/** Header length */
-		unsigned hdr_len : 4;
-		/** Message flags */
-		uint8_t flags;
-		/** Sender device ID */
-		uint16_t dev_id;
-		/** Message ID */
-		uint32_t sequence;
-		/** Message length (data only) */
-		uint16_t data_len;
-		/** Digital signature for authentication */
-		uint32_t signature;
-		/** Timestamp in uS since unix epoch */
-		uint64_t timestamp
-	} header;
-	union
-	{
-		uint32_t integer;
-		float data float_single;
-		char * data_str;
-	} data[MAX_VALUES];
+#define MSG_VERSION	0
 
+/** @todo Implement more message types */
+#define MSG_TYPE_DATA	0
+#define MSG_TYPE_START	1
+#define MSG_TYPE_STOP	2
+
+struct node;
+
+/** This message format is used by all clients
+ *
+ * @diafile msg_format.dia
+ **/
+struct msg
+{
+	/** The version specifies the format of the remaining message */
+	unsigned version	: 4;
+	/** Data or control message */
+	unsigned type		: 2;
+	/** These bits are reserved for future extensions */
+	unsigned __padding	: 2;
+	/** Length in dwords of the whole message */
+	uint8_t length;
+	/** The sequence number gets incremented by one for consecutive messages */
+	uint16_t sequence;
+	/** The message payload */
+	float data[MAX_VALUES];
 } __attribute__((packed));
-#else
-  #error "Unknown protocol version!"
-#endif
 
 /** Print a raw UDP message in human readable form.
  *
diff --git a/server/include/path.h b/server/include/path.h
index 1d332b399..75a843c35 100644
--- a/server/include/path.h
+++ b/server/include/path.h
@@ -50,8 +50,10 @@ struct path
 	unsigned long delayed;
 	/** Counter for messages which arrived multiple times */
 	unsigned long duplicated;
-	/** Counter for received messages with invalid device id or data */
+	/** Counter for received messages with invalid version or type */
 	unsigned long invalid;
+	/** Counter for skipped or filtered messages by hook */
+	unsigned long skipped;
 
 	/** The thread id for this path */
 	pthread_t tid;
diff --git a/server/src/msg.c b/server/src/msg.c
index 3f03c5e35..72ba15f03 100644
--- a/server/src/msg.c
+++ b/server/src/msg.c
@@ -14,51 +14,44 @@
 
 int msg_fprint(FILE *f, struct msg *msg)
 {
-	fprintf(f, "%-8u %-8u", msg->device, msg->sequence);
+	fprintf(f, "%-8hu", msg->sequence);
 
-	for (int i = 0; i < msg->length / sizeof(double); i++) {
+	for (int i = 0; i < msg->length; i++)
 		fprintf(f, "%-12.6f ", msg->data[i]);
-	}
 
 	fprintf(f, "\n");
 
 	return 0;
 }
 
-int msg_fscan(FILE *f, struct msg *msg)
+int msg_fscan(FILE *f, struct msg *m)
 {
-	fscanf(f, "%8hu %8u ", &msg->device, &msg->sequence);
+	fscanf(f, "%8hu ", &m->sequence);
 
-	for (int i = 0; i < msg->length / sizeof(double); i++) {
-		fscanf(f, "%12lf ", &msg->data[i]);
-	}
+	for (int i = 0; i < m->length; i++)
+		fscanf(f, "%12f ", &m->data[i]);
 
 	fscanf(f, "\n");
-
 	return 0;
 }
 
 void msg_random(struct msg *m)
 {
-	int values = m->length / sizeof(double);
-
-	for (int i = 0; i < values; i++) {
-		m->data[i] += (double) random() / RAND_MAX - .5;
-	}
+	for (int i = 0; i < m->length; i++)
+		m->data[i] += (float) random() / RAND_MAX - .5;
 
 	m->sequence++;
 }
 
 int msg_send(struct msg *m, struct node *n)
 {
-	if (sendto(n->sd, m, m->length + 8, 0,
+	if (sendto(n->sd, m, (m->length+1) * 4, 0,
 		(struct sockaddr *) &n->remote,
 		sizeof(struct sockaddr_in)) < 0)
 		perror("Failed sendto");
 
-	debug(10, "Message sent to node %s (%s:%u)", n->name,
-		inet_ntoa(n->remote.sin_addr),
-		ntohs(n->remote.sin_port));
+	debug(10, "Message sent to node '%s'", n->name);
+	if (V >= 10) msg_fprint(stdout, m);
 
 	return 0;
 }
@@ -68,7 +61,8 @@ int msg_recv(struct msg *m, struct node *n)
 	if (recv(n->sd, m, sizeof(struct msg), 0) < 0)
 		perror("Failed recv");
 
-	debug(10, "Message received from node %s", n->name);
+	debug(10, "Message received from node '%s'", n->name);
+	if (V >= 10) msg_fprint(stdout, m);
 
 	return 0;
 }
diff --git a/server/src/path.c b/server/src/path.c
index 3350d7813..0ce30c25d 100644
--- a/server/src/path.c
+++ b/server/src/path.c
@@ -70,36 +70,51 @@ static void * path_run(void *arg)
 	/* Main thread loop */
 	while (1) {
 		msg_recv(&m, p->in); /* Receive message */
-
 		p->received++;
 
-		if (m.sequence == 0 && p->sequence > 0) {
-			path_stats(p);
-			info("Simulation restarted");
+		/** Check header fields */
+		if (m.version != MSG_VERSION) {
+			p->invalid++;
+			continue;
+		}
 
-			p->sequence = 0;
-			p->received = 0;
-			p->sent = 0;
-			p->delayed = 0;
-			p->duplicated = 0;
-			p->invalid = 0;
+		if (m.type != MSG_TYPE_DATA) {
+			p->invalid++;
+			continue;
+		}
+
+		/* Check sequence number */
+		if (m.sequence <= 1) {
+			path_stats(p);
+			info("Simulation started");
+
+			p->sequence	= 0;
+			p->received	= 1;
+			p->sent		= 0;
+			p->skipped	= 0;
+			p->delayed	= 0;
+			p->duplicated	= 0;
+			p->invalid	= 0;
 		}
 		else if (m.sequence < p->sequence) {
 			p->delayed++;
+			continue;
 		}
 		else if (m.sequence == p->sequence) {
 			p->duplicated++;
+			continue;
 		}
 
-		/* Call hook */
-		if (p->hook && p->hook(&m))
+		if (p->hook && p->hook(&m)) {
+			p->skipped++;
 			continue;
+		}
 
 		/* At fixed rate mode, messages are send by another thread */
 		if (p->rate)
 			p->last = &m;
 		else
-			msg_send(p->last, p->out);
+			msg_send(&m, p->out);
 
 		p->sequence = m.sequence;
 		p->sent++;
diff --git a/server/src/random.c b/server/src/random.c
index f8ee7fb35..bfa8ef013 100644
--- a/server/src/random.c
+++ b/server/src/random.c
@@ -31,9 +31,8 @@ void tick(int sig, siginfo_t *si, void *ptr)
 
 int main(int argc, char *argv[])
 {
-	if (argc != 4) {
-		printf("Usage: %s DEVID VALUES RATE\n", argv[0]);
-		printf("  DEVID  is the device id of this node\n");
+	if (argc != 3) {
+		printf("Usage: %s VALUES RATE\n", argv[0]);
 		printf("  VALUES is the number of values a message contains\n");
 		printf("  RATE   how many messages per second\n\n");
 		printf("s2ss Simulator2Simulator Server v%s\n", VERSION);
@@ -41,10 +40,9 @@ int main(int argc, char *argv[])
 		exit(EXIT_FAILURE);
 	}
 
-	int rate = atoi(argv[3]);
+	int rate = atoi(argv[2]);
 	struct msg msg = {
-		.device = atoi(argv[1]),
-		.length = atoi(argv[2]) * sizeof(double),
+		.length = atoi(argv[1]),
 		.sequence = 0,
 		.data = { 0 }
 	};
@@ -76,7 +74,7 @@ int main(int argc, char *argv[])
 	};
 
 	/* Print header */
-	fprintf(stderr, "# %-6s %-8s %-12s\n", "dev_id", "seq_no", "data");
+	fprintf(stderr, "# %-6s%-12s\n", "seq", "data");
 
 	timer_create(CLOCKID, &sev, &t);
 	timer_settime(t, 0, &its, NULL);
diff --git a/server/src/receive.c b/server/src/receive.c
index 402778129..acf9d79e7 100644
--- a/server/src/receive.c
+++ b/server/src/receive.c
@@ -30,11 +30,11 @@ void quit(int sig, siginfo_t *si, void *ptr)
 
 int main(int argc, char *argv[])
 {
-	struct node n;
+	struct node n = {
+		.name ="node"
+	};
 	struct msg m;
 
-	memset(&n, 0, sizeof(struct node));
-
 	if (argc != 2) {
 		printf("Usage: %s LOCAL\n", argv[0]);
 		printf("  LOCAL   is a IP:PORT combination of the local host\n\n");
@@ -65,6 +65,11 @@ int main(int argc, char *argv[])
 	while (1) {
 		msg_recv(&m, &n);
 
+		if (m.version != MSG_VERSION)
+			continue;
+		if (m.type != MSG_TYPE_DATA)
+			continue;
+
 #if 1
 		struct timespec ts;
 		clock_gettime(CLOCK_REALTIME, &ts);
diff --git a/server/src/send.c b/server/src/send.c
index 714fe8172..e7adb4408 100644
--- a/server/src/send.c
+++ b/server/src/send.c
@@ -44,7 +44,9 @@ int main(int argc, char *argv[])
 		.name = "node"
 	};
 	struct msg m = {
-		.length = atoi(argv[1]) * sizeof(double)
+		.version = MSG_VERSION,
+		.type = MSG_TYPE_DATA,
+		.length = atoi(argv[1])
 	};
 
 	/* Setup signals */
@@ -69,7 +71,8 @@ int main(int argc, char *argv[])
 		n.local.sin_port = 0;
 	}
 
-	node_connect(&n);
+	if (node_connect(&n))
+		error("Failed to connect node");
 
 	while (!feof(stdin)) {
 		msg_fscan(stdin, &m);
diff --git a/server/src/test.c b/server/src/test.c
index b1bd3518c..0ba5eaee0 100644
--- a/server/src/test.c
+++ b/server/src/test.c
@@ -64,7 +64,6 @@ int main(int argc, char *argv[])
 
 	if (!strcmp(argv[1], "latency")) {
 		struct msg m = {
-			.device = 99,
 			.sequence = 0
 		};
 		struct timespec *ts1 = (struct timespec *) &m.data;