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Implement TCP Heartbeat

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Some users have reported issues where the TCP link to dump1090 can be
lost at times of low traffic density - typically in the middle of the
night. One possible reason for this is that some routers drop the link
if there is no traffic for a predetermined period.

To try and resolve this, dump1090 now sends a 'null' packet consisting
of 7 "0x00" bytes approximately once a  minute if there is no real
received traffic during this time. This packet should be discarded by
the application receiving the dump1090 because it will have an invalid
checksum, and ICAO address 0x000000 is also invalid. However, this null
packet should be enough to keep routers alive.
This commit is contained in:
Malcolm Robb 2014-03-11 01:09:49 +00:00
parent 4a438d6e34
commit f7843c1691
5 changed files with 32 additions and 2 deletions

22
mode_s.c
View file

@ -1812,6 +1812,25 @@ void detectModeS(uint16_t *m, uint32_t mlen) {
Modes.net_output_raw_rate_count = 0;
}
}
else if ( (Modes.net)
&& (Modes.net_heartbeat_rate)
&& ((++Modes.net_heartbeat_count) > Modes.net_heartbeat_rate) ) {
//
// We haven't received any Mode A/C/S messages for some time. To try and keep any TCP
// links alive, send a null frame. This will help stop any routers discarding our TCP
// link which will cause an un-recoverable link error if/when a real frame arrives.
//
// Fudge up a null message
memset(&mm, 0, sizeof(mm));
mm.msgbits = MODES_SHORT_MSG_BITS;
mm.timestampMsg = Modes.timestampBlk;
// Feed output clients
modesQueueOutput(&mm);
// Reset the heartbeat counter
Modes.net_heartbeat_count = 0;
}
}
//
//=========================================================================
@ -1836,6 +1855,9 @@ void useModesMessage(struct modesMessage *mm) {
// Feed output clients
if (Modes.net) {modesQueueOutput(mm);}
// Heartbeat not required whilst we're seeing real messages
Modes.net_heartbeat_count = 0;
}
}
//