satcat5::udp::KeepAlive Class Reference

Detailed Description

Send and receive keep-alive messages.

In some networks, idle endpoints may be expected to periodically send UDP messages to a designated UDP port, to indicate that the connection is still valid. Recipients should immediately discard such messages with no further action.

This class binds the incoming UDP port, to prevent false-alarm "port-unreachable" ICMP errors from being sent in response.

Optionally, this class may also be used to send keep-alive messages, defaulting to the broadcast addresss (255.255.255.255). To enable this feature, call timer_once or timer_every.

Definition at line 25 of file udp_keep_alive.h.

#include <udp_keep_alive.h>

Inheritance diagram for satcat5::udp::KeepAlive:

Collaboration diagram for satcat5::udp::KeepAlive:

Public Member Functions
	KeepAlive (satcat5::udp::Dispatch *iface, satcat5::udp::Port port, const char *label=nullptr)
	Bind this object to a network interface and UDP port. More...
void	connect (const satcat5::ip::Addr &dstaddr, const satcat5::eth::VlanTag &vtag=satcat5::eth::VTAG_NONE)
	Connect to a specific destination address. More...
void	send_now (const char *msg)
	Immediately send a keep-alive, with an optional message.
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.

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.

Protected Attributes
satcat5::udp::Address	m_addr
const char *const	m_label
satcat5::net::Type	m_filter
	Incoming packet filter.

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

Constructor & Destructor Documentation

KeepAlive()

KeepAlive::KeepAlive ( satcat5::udp::Dispatch *  iface, satcat5::udp::Port  port, const char *  label = nullptr  )

explicit

Bind this object to a network interface and UDP port.

Parameters

iface	UDP network interface.
port	UDP port number (incoming + outgoing).
label	Optional message for each outgoing packet.

Definition at line 11 of file udp_keep_alive.cc.

Member Function Documentation

connect()

void KeepAlive::connect	(	const satcat5::ip::Addr &	dstaddr,
		const satcat5::eth::VlanTag &	vtag = satcat5::eth::VTAG_NONE
	)

Connect to a specific destination address.

During object creation, the destination defaults to broadcast (255.255.255.255). This method changes the destination address.

Definition at line 27 of file udp_keep_alive.cc.

frame_rcvd()

void KeepAlive::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 44 of file udp_keep_alive.cc.

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

• udp_keep_alive.h
• udp_keep_alive.cc