diff --git a/include/villas/webmsg_format.h b/include/villas/webmsg_format.h
new file mode 100644
index 000000000..3873d4470
--- /dev/null
+++ b/include/villas/webmsg_format.h
@@ -0,0 +1,101 @@
+/** Binary websocket message format
+ *
+ * @file
+ * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
+ * @copyright 2014-2016, Institute for Automation of Complex Power Systems, EONERC
+ *   This file is part of VILLASnode. All Rights Reserved. Proprietary and confidential.
+ *   Unauthorized copying of this file, via any medium is strictly prohibited. 
+ *********************************************************************************/
+
+#ifndef _WEBMSG_FORMAT_H_
+#define _WEBMSG_FORMAT_H_
+
+#include <stdint.h>
+
+#ifdef __linux__
+  #define _BSD_SOURCE		1
+  #include <endian.h>
+#elif defined(__PPC__) /* Xilinx toolchain */
+  #include <lwip/arch.h>
+#endif
+
+/** The current version number for the message format */
+#define WEBMSG_VERSION		1
+
+/** @todo Implement more message types */
+#define WEBMSG_TYPE_DATA	0 /**< Message contains float values */
+#define WEBMSG_TYPE_START	1 /**< Message marks the beginning of a new simulation case */
+#define WEBMSG_TYPE_STOP	2 /**< Message marks the end of a simulation case */
+
+#define WEBMSG_ENDIAN_LITTLE	0 /**< Message values are in little endian format (float too!) */
+#define WEBMSG_ENDIAN_BIG	1 /**< Message values are in bit endian format */
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+  #define WEBMSG_ENDIAN_HOST	MSG_ENDIAN_LITTLE
+#elif BYTE_ORDER == BIG_ENDIAN
+  #define WEBMSG_ENDIAN_HOST	MSG_ENDIAN_BIG
+#else
+  #error "Unknown byte order!"
+#endif
+
+/** The total size in bytes of a message */
+#define WEBMSG_LEN(values)	(sizeof(struct msg) + MSG_DATA_LEN(values))
+
+/** The length of \p values values in bytes. */
+#define WEBMSG_DATA_LEN(values)	(sizeof(float) * (values))
+
+/** The offset to the first data value in a message. */
+#define WEBMSG_DATA_OFFSET(msg)	((char *) (msg) + offsetof(struct msg, data))
+
+/** Initialize a message with default values */
+#define WEBMSG_INIT(len, seq) (struct msg) {\
+	.version  = MSG_VERSION,	\
+	.type     = MSG_TYPE_DATA,	\
+	.endian   = MSG_ENDIAN_HOST,	\
+	.length   = len,	 	\
+	.sequence = seq			\
+}
+
+/** The timestamp of a message in struct timespec format */
+#define WEBMSG_TS(msg) (struct timespec) {\
+	.tv_sec  = (msg)->ts.sec,	\
+	.tv_nsec = (msg)->ts.nsec	\
+}
+
+/** This message format is used by all clients
+ *
+ * @diafile msg_format.dia
+ **/
+struct webmsg
+{
+#if BYTE_ORDER == BIG_ENDIAN
+	unsigned version: 4;	/**< Specifies the format of the remaining message (see MGS_VERSION) */
+	unsigned type	: 2;	/**< Data or control message (see MSG_TYPE_*) */
+	unsigned endian	: 1;	/**< Specifies the byteorder of the message (see MSG_ENDIAN_*) */
+	unsigned rsvd1	: 1;	/**< Reserved bits */
+#elif BYTE_ORDER == LITTLE_ENDIAN
+	unsigned rsvd1	: 1;	/**< Reserved bits */
+	unsigned endian	: 1;	/**< Specifies the byteorder of the message (see MSG_ENDIAN_*) */
+	unsigned type	: 2;	/**< Data or control message (see MSG_TYPE_*) */
+	unsigned version: 4;	/**< Specifies the format of the remaining message (see MGS_VERSION) */
+#endif
+
+	uint8_t src_node;	/**< Reserved bits */
+	
+	uint16_t length;	/**< The number of values in msg::data[]. Endianess is specified in msg::endian. */
+	uint32_t sequence;	/**< The sequence number is incremented by one for consecutive messages. Endianess is specified in msg::endian. */
+	
+	/** A timestamp per message. Endianess is specified in msg::endian. */
+	struct {
+		uint32_t sec;	/**< Seconds since 1970-01-01 00:00:00 */
+		uint32_t nsec;	/**< Nanoseconds of the current second. */
+	} ts;
+
+	/** The message payload. Endianess is specified in msg::endian. */
+	union {
+		float    f;	/**< Floating point values (note msg::endian) */
+		uint32_t i;	/**< Integer values (note msg::endian) */
+	} data[];
+} __attribute__((packed));
+
+#endif /* _WEBMSG_FORMAT_H_ */