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| void | stun_timer_start () |
| void | stun_timer_start_reliable () |
| StunUsageTimerReturn | stun_timer_refresh () |
| unsigned | stun_timer_remainder () |
| typedef | StunTimer |
| enum | StunUsageTimerReturn |
| #define | STUN_TIMER_DEFAULT_MAX_RETRANSMISSIONS |
| #define | STUN_TIMER_DEFAULT_RELIABLE_TIMEOUT |
| #define | STUN_TIMER_DEFAULT_TIMEOUT |
The STUN timer usage is a set of helpful utility functions that allows you to easily track when a STUN message should be retransmitted or considered as timed out.
Example 3. Simple example on how to use the timer usage
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StunTimer timer; unsigned remainder; StunUsageTimerReturn ret; // Build the message, etc.. ... // Send the message and start the timer send(socket, request, sizeof(request)); stun_timer_start(&timer, STUN_TIMER_DEFAULT_TIMEOUT, STUN_TIMER_DEFAULT_MAX_RETRANSMISSIONS); // Loop until we get the response for (;;) { remainder = stun_timer_remainder(&timer); // Poll the socket until data is received or the timer expires if (poll (&pollfd, 1, delay) <= 0) { // Time out and no response was received ret = stun_timer_refresh (&timer); if (ret == STUN_USAGE_TIMER_RETURN_TIMEOUT) { // Transaction timed out break; } else if (ret == STUN_USAGE_TIMER_RETURN_RETRANSMIT) { // A retransmission is necessary send(socket, request, sizeof(request)); continue; } else if (ret == STUN_USAGE_TIMER_RETURN_SUCCESS) { // The refresh succeeded and nothing has to be done, continue polling continue; } } else { // We received a response, read it recv(socket, response, sizeof(response)); break; } } // Check if the transaction timed out or not if (ret == STUN_USAGE_TIMER_RETURN_TIMEOUT) { // do whatever needs to be done in that case } else { // Parse the response } |
void stun_timer_start (StunTimer *timer,unsigned int initial_timeout,unsigned int max_retransmissions);
Starts a STUN transaction retransmission timer.
This should be called as soon as you send the message for the first time on
a UDP socket.
The timeout before the next retransmission is set to initial_timeout
, then
each time a packet is retransmited, that timeout will be doubled, until the
max_retransmissions
retransmissions limit is reached.
To determine the total timeout value, one can use the following equation :
total_timeout = initial_timeout * (2^(max_retransmissions + 1) - 1);
See also: STUN_TIMER_DEFAULT_TIMEOUT
See also: STUN_TIMER_DEFAULT_MAX_RETRANSMISSIONS
void stun_timer_start_reliable (StunTimer *timer,unsigned int initial_timeout);
Starts a STUN transaction retransmission timer for a reliable transport. This should be called as soon as you send the message for the first time on a TCP socket
timer |
The StunTimer to start |
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initial_timeout |
The initial timeout to use before the first retransmission |
StunUsageTimerReturn
stun_timer_refresh (StunTimer *timer);
Updates a STUN transaction retransmission timer.
typedef struct stun_timer_s StunTimer;
An opaque structure representing a STUN transaction retransmission timer
Return value of stun_usage_timer_refresh() which provides you with status
information on the timer.
#define STUN_TIMER_DEFAULT_MAX_RETRANSMISSIONS 3
The default maximum retransmissions before declaring that the transaction timed out.
#define STUN_TIMER_DEFAULT_RELIABLE_TIMEOUT 2000
The default intial timeout to use for a reliable timer
The idea with this value is that stun request sent over udp or tcp should fail at the same time, with an initial default timeout set to 500ms.
#define STUN_TIMER_DEFAULT_TIMEOUT 500
The default intial timeout to use for the timer This timeout is used for discovering server reflexive and relay candidates, and also for keepalives, and turn refreshes.
This value is important because it defines how much time will be required to discover our local candidates, and this is an uncompressible delay before the agent signals that candidates gathering is done.
The overall delay required for the discovery stun requests is computed as follow, with 3 retransmissions and an initial delay of 500ms : 500 * ( 1 + 2 + 1 ) = 2000 ms The timeout doubles at each retransmission, except for the last one.