diff --git a/Makefile.dep b/Makefile.dep
index 2eb1d993dab40183a5d21f90261bbb2208fca0f4..baacd4f358c739d8161ec8a63b037c7f2f3371e4 100644
--- a/Makefile.dep
+++ b/Makefile.dep
@@ -19,6 +19,11 @@ ifneq (,$(filter nhdp,$(USEMODULE)))
USEMODULE += oonf_rfc5444
endif
+ifneq (,$(filter sntp,$(USEMODULE)))
+ USEMODULE += gnrc_sock_udp
+ USEMODULE += xtimer
+endif
+
ifneq (,$(filter gnrc_netdev_default,$(USEMODULE)))
USEMODULE += gnrc_netif
USEMODULE += gnrc_netdev2
diff --git a/sys/Makefile b/sys/Makefile
index 6f53b2bdaa05811b6b37a44e293c4aa90193a992..99ddbaba88a1cd50617eb7713f82896563591420 100644
--- a/sys/Makefile
+++ b/sys/Makefile
@@ -89,6 +89,10 @@ ifneq (,$(filter gnrc_uhcpc,$(USEMODULE)))
DIRS += net/gnrc/application_layer/uhcpc
endif
+ifneq (,$(filter sntp,$(USEMODULE)))
+ DIRS += net/application_layer/sntp
+endif
+
ifneq (,$(filter netopt,$(USEMODULE)))
DIRS += net/crosslayer/netopt
endif
diff --git a/sys/include/net/ntp_packet.h b/sys/include/net/ntp_packet.h
new file mode 100644
index 0000000000000000000000000000000000000000..c9e84b18e3775b3c67b6cbed7b6302afc09f1286
--- /dev/null
+++ b/sys/include/net/ntp_packet.h
@@ -0,0 +1,167 @@
+/*
+ * Copyright (C) 2016 Luminița Lăzărescu <cluminita.lazarescu@gmail.com>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup net_ntp_packet NTP Packet
+ * @ingroup net
+ * @brief The NTP packet module provides functionality to manipulate the NTP header
+ * @{
+ *
+ * @file
+ * @brief NTP packet definitions
+ *
+ * @author Luminița Lăzărescu <cluminita.lazarescu@gmail.com>
+ * @author Martine Lenders <m.lenders@fu-berlin.de>
+ */
+
+#ifndef NTP_PACKET_H_
+#define NTP_PACKET_H_
+
+#include <stdint.h>
+#include "byteorder.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @{
+ * @brief Bit positions and masks for ntp_packet_t::li_vn_mode
+ */
+/**
+ * @brief Leap indicator position
+ */
+#define NTP_PACKET_LI_POS (6U)
+#define NTP_PACKET_LI_MASK (0xc0) /**< leap indicator mask */
+#define NTP_PACKET_VN_POS (3U) /**< version position */
+#define NTP_PACKET_VN_MASK (0x38) /**< version mask */
+#define NTP_PACKET_MODE_MASK (0x07) /**< mode mask */
+/** @} */
+
+#define NTP_VERSION (4U) /**< NTP version */
+#define NTP_PORT (123U) /**< NTP port number */
+
+/**
+ * @brief NTP modes
+ */
+typedef enum {
+ NTP_MODE_RESERVED = 0, /**< reserved */
+ NTP_MODE_SYM_ACTIVE, /**< symmetric active */
+ NTP_MODE_SYM_PASSIVE, /**< symmetric passive */
+ NTP_MODE_CLIENT, /**< client */
+ NTP_MODE_SERVER, /**< server */
+ NTP_MODE_BROADCAST, /**< broadcast */
+ NTP_MODE_PRIV /**< reserved for private use */
+} ntp_mode_t;
+
+/**
+ * @brief NTP timestamp
+ *
+ * @see [RFC 5905, Section 6](https://tools.ietf.org/html/rfc5905#section-6)
+ */
+typedef struct __attribute__((packed)) {
+ network_uint32_t seconds; /**< seconds since 1 January 1900 00:00 UTC */
+ network_uint32_t fraction; /**< fraction of seconds in 232 picoseconds */
+} ntp_timestamp_t;
+
+/**
+ * @brief NTP packet
+ *
+ * @see [RFC 5905, Section 7.3](https://tools.ietf.org/html/rfc5905#section-7.3)
+ */
+typedef struct __attribute__((packed)) {
+ uint8_t li_vn_mode; /**< leap indicator, version and mode */
+ uint8_t stratum; /**< stratum */
+ uint8_t poll; /**< poll in log2 seconds */
+ uint8_t precision; /**< precision in log2 seconds */
+ network_uint32_t root_delay; /**< root delay in NTP short format */
+ network_uint32_t root_dispersion; /**< root dispersion in NTP short format */
+ network_uint32_t reference_id; /**< reference ID */
+ ntp_timestamp_t reference; /**< reference timestamp */
+ ntp_timestamp_t origin; /**< origin timesptamp */
+ ntp_timestamp_t receive; /**< receive timestamp */
+ ntp_timestamp_t transmit; /**< transmit timestamp */
+} ntp_packet_t;
+
+/**
+ * @brief Set leap indicator in a NTP packet
+ *
+ * @param[in] packet The NTP packet
+ * @param[in] li Leap indicator
+ */
+static inline void ntp_packet_set_li(ntp_packet_t *packet, uint8_t li)
+{
+ packet->li_vn_mode &= ~NTP_PACKET_LI_MASK;
+ packet->li_vn_mode |= li << NTP_PACKET_LI_POS;
+}
+
+/**
+ * @brief Set version in a NTP packet
+ *
+ * @param[in] packet The NTP packet
+ */
+static inline void ntp_packet_set_vn(ntp_packet_t *packet)
+{
+ packet->li_vn_mode &= ~NTP_PACKET_VN_MASK;
+ packet->li_vn_mode |= (NTP_VERSION << NTP_PACKET_VN_POS) & NTP_PACKET_VN_MASK;
+}
+
+/**
+ * @brief Set mode in a NTP packet
+ *
+ * @param[in] packet The NTP packet
+ * @param[in] mode Mode
+ */
+static inline void ntp_packet_set_mode(ntp_packet_t *packet, ntp_mode_t mode)
+{
+ packet->li_vn_mode &= ~NTP_PACKET_MODE_MASK;
+ packet->li_vn_mode |= mode & NTP_PACKET_MODE_MASK;
+}
+
+/**
+ * @brief Get leap indicator from a NTP packet
+ *
+ * @param[in] packet The NTP packet
+ *
+ * @return The leap indicator of @p packet
+ */
+static inline uint8_t ntp_packet_get_li(ntp_packet_t *packet)
+{
+ return (packet->li_vn_mode & NTP_PACKET_LI_MASK) >> NTP_PACKET_LI_POS;
+}
+
+/**
+ * @brief Get version from a NTP packet
+ *
+ * @param[in] packet The NTP packet
+ *
+ * @return The version of @p packet
+ */
+static inline uint8_t ntp_packet_get_vn(ntp_packet_t *packet)
+{
+ return (packet->li_vn_mode & NTP_PACKET_VN_MASK) >> NTP_PACKET_VN_POS;
+}
+
+/**
+ * @brief Get mode from a NTP packet
+ *
+ * @param[in] packet The NTP packet
+ *
+ * @return The version of @p packet
+ */
+static inline ntp_mode_t ntp_packet_get_mode(ntp_packet_t *packet)
+{
+ return (packet->li_vn_mode & NTP_PACKET_MODE_MASK);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NTP_PACKET_H_ */
+/** @} */
diff --git a/sys/include/net/sntp.h b/sys/include/net/sntp.h
new file mode 100644
index 0000000000000000000000000000000000000000..7390438fcc227cabfdb33ad99e085a08d2fdc27b
--- /dev/null
+++ b/sys/include/net/sntp.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2016 Luminița Lăzărescu <cluminita.lazarescu@gmail.com>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup net_sntp Simple Network Time Protocol
+ * @ingroup net
+ * @brief Simple Network Time Protocol (SNTP) implementation
+ * @{
+ *
+ * @file
+ * @brief SNTP definitions
+ *
+ * @author Luminița Lăzărescu <cluminita.lazarescu@gmail.com>
+ * @author Martine Lenders <m.lenders@fu-berlin.de>
+ */
+
+#ifndef SNTP_H_
+#define SNTP_H_
+
+#include <stdint.h>
+#include "net/sock/udp.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Synchronize with time server
+ *
+ * @param[in] server The time server
+ * @param[in] timeout Timeout for the server response
+ *
+ * @return 0 on success
+ * @return Negative number on error
+ */
+int sntp_sync(sock_udp_ep_t *server, uint32_t timeout);
+
+/**
+ * @brief Get real time offset from system time as returned by @ref xtimer_now64()
+ *
+ * @return Real time offset in microseconds relative to 1900-01-01 00:00 UTC
+ */
+int64_t sntp_get_offset(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SNTP_H_ */
+/** @} */
diff --git a/sys/net/application_layer/sntp/Makefile b/sys/net/application_layer/sntp/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..b0ece6866351af60f7f3e227a9bd6386e09bd791
--- /dev/null
+++ b/sys/net/application_layer/sntp/Makefile
@@ -0,0 +1,2 @@
+MODULE = sntp
+include $(RIOTBASE)/Makefile.base
diff --git a/sys/net/application_layer/sntp/sntp.c b/sys/net/application_layer/sntp/sntp.c
new file mode 100644
index 0000000000000000000000000000000000000000..c8fbb443bc306ac6184539ef582c9c68415487e7
--- /dev/null
+++ b/sys/net/application_layer/sntp/sntp.c
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2016 Luminița Lăzărescu <cluminita.lazarescu@gmail.com>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ * @brief SNTP implementation
+ *
+ * @author Luminița Lăzărescu <cluminita.lazarescu@gmail.com>
+ * @author Martine Lenders <m.lenders@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include <string.h>
+#include "net/sntp.h"
+#include "net/ntp_packet.h"
+#include "net/sock/udp.h"
+#include "xtimer.h"
+#include "mutex.h"
+#include "byteorder.h"
+
+#define ENABLE_DEBUG (0)
+#include "debug.h"
+
+static sock_udp_t _sntp_sock;
+static int64_t _sntp_offset = 0;
+static mutex_t _sntp_mutex = MUTEX_INIT;
+static ntp_packet_t _sntp_packet;
+
+int sntp_sync(sock_udp_ep_t *server, uint32_t timeout)
+{
+ int result;
+
+ mutex_lock(&_sntp_mutex);
+ if ((result = sock_udp_create(&_sntp_sock,
+ NULL,
+ server,
+ 0)) < 0) {
+ DEBUG("Error creating UDP sock\n");
+ mutex_unlock(&_sntp_mutex);
+ return result;
+ }
+ memset(&_sntp_packet, 0, sizeof(_sntp_packet));
+ ntp_packet_set_vn(&_sntp_packet);
+ ntp_packet_set_mode(&_sntp_packet, NTP_MODE_CLIENT);
+
+ if ((result = (int)sock_udp_send(&_sntp_sock,
+ &_sntp_packet,
+ sizeof(_sntp_packet),
+ NULL)) < 0) {
+ DEBUG("Error sending message\n");
+ sock_udp_close(&_sntp_sock);
+ mutex_unlock(&_sntp_mutex);
+ return result;
+ }
+ if ((result = (int)sock_udp_recv(&_sntp_sock,
+ &_sntp_packet,
+ sizeof(_sntp_packet),
+ timeout,
+ NULL)) < 0) {
+ DEBUG("Error receiving message\n");
+ sock_udp_close(&_sntp_sock);
+ mutex_unlock(&_sntp_mutex);
+ return result;
+ }
+ sock_udp_close(&_sntp_sock);
+ _sntp_offset = (byteorder_ntohl(_sntp_packet.transmit.seconds) * SEC_IN_USEC) +
+ ((byteorder_ntohl(_sntp_packet.transmit.fraction) * 232)
+ / 1000000) - xtimer_now64();
+ mutex_unlock(&_sntp_mutex);
+ return 0;
+}
+
+int64_t sntp_get_offset(void)
+{
+ int64_t result;
+
+ mutex_lock(&_sntp_mutex);
+ result = _sntp_offset;
+ mutex_unlock(&_sntp_mutex);
+ return result;
+}
diff --git a/sys/shell/commands/Makefile b/sys/shell/commands/Makefile
index b0c4baa2bb9e92dd592b1785ef3c76808fb777b7..0e0dc877b6d670f203fdcd443b87e83d09980dc8 100644
--- a/sys/shell/commands/Makefile
+++ b/sys/shell/commands/Makefile
@@ -66,6 +66,9 @@ endif
ifneq (,$(filter ccn-lite-utils,$(USEMODULE)))
SRC += sc_ccnl.c
endif
+ifneq (,$(filter sntp,$(USEMODULE)))
+ SRC += sc_sntp.c
+endif
# TODO
# Conditional building not possible at the moment due to
diff --git a/sys/shell/commands/sc_sntp.c b/sys/shell/commands/sc_sntp.c
new file mode 100644
index 0000000000000000000000000000000000000000..87cab4abc0a38dba68927e5a88fcbcb74beb8cca
--- /dev/null
+++ b/sys/shell/commands/sc_sntp.c
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2016 Luminița Lăzărescu <cluminita.lazarescu@gmail.com>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup sys_shell_commands
+ * @{
+ *
+ * @file
+ * @brief Prints the real time offset from the system time
+ *
+ * @author Luminița Lăzărescu <cluminita.lazarescu@gmail.com>
+ */
+
+
+#include "net/sntp.h"
+#include "net/ntp_packet.h"
+#include "net/af.h"
+#include "net/ipv6/addr.h"
+
+#define _DEFAULT_TIMEOUT (5000U);
+
+static void _usage(char *cmd)
+{
+ printf("Usage: %s <server addr> [<timeout>]\n", cmd);
+ puts("default: timeout = 5000");
+}
+
+int _ntpdate(int argc, char **argv)
+{
+ uint32_t timeout = _DEFAULT_TIMEOUT;
+
+ if (argc < 2) {
+ _usage(argv[0]);
+ return 1;
+ }
+ sock_udp_ep_t server = { .port = NTP_PORT, .family = AF_INET6 };
+ ipv6_addr_from_str((ipv6_addr_t *)&server.addr, argv[1]);
+ if (argc > 2) {
+ timeout = atoi(argv[2]);
+ }
+ if (sntp_sync(&server, timeout) < 0) {
+ puts("Error in synchronization");
+ return 1;
+ }
+ printf("Offset: %i\n", (int)sntp_get_offset());
+ return 0;
+}
diff --git a/sys/shell/commands/shell_commands.c b/sys/shell/commands/shell_commands.c
index 39125e34afa0628c6ddd5aa9160f9a29de8f7e63..c6a2d1f83fe8b64e249f7344ccee8d26b6637fb9 100644
--- a/sys/shell/commands/shell_commands.c
+++ b/sys/shell/commands/shell_commands.c
@@ -129,6 +129,10 @@ extern int _ccnl_interest(int argc, char **argv);
extern int _ccnl_fib(int argc, char **argv);
#endif
+#ifdef MODULE_SNTP
+extern int _ntpdate(int argc, char **argv);
+#endif
+
const shell_command_t _shell_command_list[] = {
{"reboot", "Reboot the node", _reboot_handler},
#ifdef MODULE_CONFIG
@@ -209,10 +213,13 @@ const shell_command_t _shell_command_list[] = {
{"saul", "interact with sensors and actuators using SAUL", _saul },
#endif
#ifdef MODULE_CCN_LITE_UTILS
- { "ccnl_open", "opens an interface or socket", _ccnl_open},
- { "ccnl_int", "sends an interest", _ccnl_interest},
- { "ccnl_cont", "create content and populated it", _ccnl_content},
- { "ccnl_fib", "shows or modifies the CCN-Lite FIB", _ccnl_fib},
+ { "ccnl_open", "opens an interface or socket", _ccnl_open },
+ { "ccnl_int", "sends an interest", _ccnl_interest },
+ { "ccnl_cont", "create content and populated it", _ccnl_content },
+ { "ccnl_fib", "shows or modifies the CCN-Lite FIB", _ccnl_fib },
+#endif
+#ifdef MODULE_SNTP
+ { "ntpdate", "synchronizes with a remote time server", _ntpdate },
#endif
{NULL, NULL, NULL}
};