satcat5::ntp::Client Class Reference

Detailed Description

Client and/or server for the Network Time Protocol (NTP).

This class implements a combined client and server for the Network Time Protocol, version 4 (NTPv4), as defined in IETF RFC-5905. The client follows the simplified rules (aka "SNTP") defined in Section 14, with no more than one upstream parent and no peers in the same stratum.

In all modes, the underlying clock is a ptp::TrackingClock object. In server mode, the clock is used as a read-only reference. In client mode, the class will issue ptp::Callback notifications that can be used to discipline the clock (see also: "ptp_tracking.h").

Server mode is enabled using server_start(...) method. If active, the class responds to valid incoming queries immediately, with no attempt to maintain state or rate-limiting. This behavior is not suited for untrusted networks and may be changed in future updates. Server mode and client mode are not mutually exclusive.

Client mode is activated by calling client_connect(...). While client mode is active, the class regularly sends a query to the server; whenever a valid reply is received, it notifies any attached ptp::Callback objects. (See "ptp_tracking.h" for useful examples.) The callbacks should adjust the underlying clock to bring everything into sync; this class does not implement the recommended filter algorithms from Sections 10 and 12.

Broadcast mode and peer-to-peer associations are not currently supported.

Definition at line 43 of file ntp_client.h.

#include <ntp_client.h>

Inheritance diagram for satcat5::ntp::Client:

Collaboration diagram for satcat5::ntp::Client:

Public Member Functions
	Client (satcat5::ptp::TrackingClock *refclk, satcat5::udp::Dispatch *iface)
	Set the reference clock and network interface for this client.
void	client_connect (const satcat5::ip::Addr &server, s8 poll_rate=satcat5::ntp::Header::TIME_1MIN)
	Enable client mode by connecting to the specified server. More...
void	client_close ()
	Close the connection to a remote server.
bool	client_ok ()
	Is the client currently connected?
void	client_set_rate (s8 poll_rate)
	Set the client polling rate. More...
void	server_start (u8 stratum)
	Enable or disable server mode.
u64	ntp_now () const
	Get the current time in NTP format.
u64	to_ntp (const satcat5::ptp::Time &t) const
	Convert any PTP timestamp to NTP format.
satcat5::ptp::Time	to_ptp (u64 t) const
	Convert NTP timestamp to PTP format.
void	timer_once (unsigned msec)
	Configure a one-time notification after X milliseconds.
void	timer_every (unsigned msec)
	Configure a repeating notification every X milliseconds.
void	timer_stop ()
	Stop all future notifications.
unsigned	timer_interval () const
	Accessor for recurring timer interval, if one is set.
unsigned	timer_remaining () const
	Accessor for time to next event, if one is set.
void	add_callback (satcat5::ptp::Callback *callback)
void	remove_callback (satcat5::ptp::Callback *callback)

Static Public Member Functions
static unsigned	count_timer ()
	Count all objects of this type, including idle timers.

Protected Member Functions
void	frame_rcvd (satcat5::io::LimitedRead &src) override
	Dispatch calls frame_rcvd(...) for each incoming frame with with a matching net::Type value. More...
void	timer_event () override
	Child class MUST override this method.
void	rcvd_reply (const satcat5::ntp::Header &msg, u64 rxtime)
bool	send_reply (const satcat5::ntp::Header &msg, u64 rxtime)
bool	send_query ()
void	notify_callbacks (const satcat5::ptp::Measurement &meas)
	Notify all Callback objects of a new Measurement.

Protected Attributes
satcat5::ptp::TrackingClock *const	m_refclk
satcat5::udp::Address	m_iface
u64	m_reftime
u8	m_leap
u8	m_stratum
s8	m_rate
satcat5::net::Type	m_filter
	Incoming packet filter.
satcat5::util::List< satcat5::ptp::Callback >	m_callbacks
	Linked list of registered callback objects.

Private Member Functions
void	query (unsigned elapsed_msec)

Private Attributes
satcat5::net::Protocol *	m_next
	Linked list of Protocols.
unsigned	m_trem
unsigned	m_tnext

Member Function Documentation

client_connect()

void Client::client_connect	(	const satcat5::ip::Addr &	server,
		s8	poll_rate = satcat5::ntp::Header::TIME_1MIN
	)

Enable client mode by connecting to the specified server.

Polling rate is once every 2^N seconds (see ntp::Header).

Definition at line 57 of file ntp_client.cc.

client_set_rate()

void Client::client_set_rate

(

s8

poll_rate

)

Set the client polling rate.

Polling rate is once every 2^N seconds (see ntp::Header).

Definition at line 68 of file ntp_client.cc.

frame_rcvd()

void Client::frame_rcvd ( satcat5::io::LimitedRead &  src )

overrideprotectedvirtual

Dispatch calls frame_rcvd(...) for each incoming frame with with a matching net::Type value.

The child class SHOULD read the frame contents from the provided "src" object, which is only valid until the function returns.

To send a reply:

• Call m_iface->open_reply() to obtain a Writable object. (This also writes out any applicable frame headers.)
• Write frame contents, then call write_finalize().

The child class MUST override this method.

Implements satcat5::net::Protocol.

Definition at line 73 of file ntp_client.cc.

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The documentation for this class was generated from the following files:

• ntp_client.h
• ntp_client.cc