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mqtt: send ping at upkeep interval

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Closes #16975
This commit is contained in:
Christian Schmitz 2025-04-05 13:28:03 +02:00 • committed by Daniel Stenberg
parent 56e40ae6a5
commit 8ad0243e1f
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4 changed files with 66 additions and 1 deletions
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56
lib/mqtt.c
View file

@ -46,12 +46,16 @@
/* The last #include file should be: */
#include "memdebug.h"
/* first byte is command.
second byte is for flags. */
#define MQTT_MSG_CONNECT 0x10
/* #define MQTT_MSG_CONNACK 0x20 */
#define MQTT_MSG_PUBLISH 0x30
#define MQTT_MSG_SUBSCRIBE 0x82
#define MQTT_MSG_SUBACK 0x90
#define MQTT_MSG_DISCONNECT 0xe0
#define MQTT_MSG_PINGREQ 0xC0
#define MQTT_MSG_PINGRESP 0xD0
#define MQTT_CONNACK_LEN 2
#define MQTT_SUBACK_LEN 3
@ -125,6 +129,7 @@ static CURLcode mqtt_send(struct Curl_easy *data,
CURLcode result = Curl_xfer_send(data, buf, len, FALSE, &n);
if(result)
return result;
mq->lastTime = Curl_now();
Curl_debug(data, CURLINFO_HEADER_OUT, buf, (size_t)n);
if(len != n) {
size_t nsend = len - n;
@ -687,6 +692,9 @@ MQTT_SUBACK_COMING:
goto end;
}
/* we received something */
mq->lastTime = Curl_now();
/* if QoS is set, message contains packet id */
result = Curl_client_write(data, CLIENTWRITE_BODY, buffer, nread);
if(result)
@ -709,9 +717,13 @@ end:
static CURLcode mqtt_do(struct Curl_easy *data, bool *done)
{
struct MQTT *mq = data->req.p.mqtt;
CURLcode result = CURLE_OK;
*done = FALSE; /* unconditionally */
mq->lastTime = Curl_now();
mq->pingsent = FALSE;
result = mqtt_connect(data);
if(result) {
failf(data, "Error %d sending MQTT CONNECT request", result);
@ -732,6 +744,35 @@ static CURLcode mqtt_done(struct Curl_easy *data,
return CURLE_OK;
}
/* we ping regularly to avoid being disconnected by the server */
static CURLcode mqtt_ping(struct Curl_easy *data)
{
CURLcode result = CURLE_OK;
struct connectdata *conn = data->conn;
struct mqtt_conn *mqtt = &conn->proto.mqtt;
struct MQTT *mq = data->req.p.mqtt;
if(mqtt->state == MQTT_FIRST &&
!mq->pingsent &&
data->set.upkeep_interval_ms > 0) {
struct curltime t = Curl_now();
timediff_t diff = Curl_timediff(t, mq->lastTime);
if(diff > data->set.upkeep_interval_ms) {
/* 0xC0 is PINGREQ, and 0x00 is remaining length */
unsigned char packet[2] = { 0xC0, 0x00 };
size_t packetlen = sizeof(packet);
result = mqtt_send(data, (char *)packet, packetlen);
if(!result) {
mq->pingsent = TRUE;
}
infof(data, "mqtt_ping: sent ping request.");
}
}
return result;
}
static CURLcode mqtt_doing(struct Curl_easy *data, bool *done)
{
CURLcode result = CURLE_OK;
@ -750,6 +791,10 @@ static CURLcode mqtt_doing(struct Curl_easy *data, bool *done)
return result;
}
result = mqtt_ping(data);
if(result)
return result;
infof(data, "mqtt_doing: state [%d]", (int) mqtt->state);
switch(mqtt->state) {
case MQTT_FIRST:
@ -764,6 +809,10 @@ static CURLcode mqtt_doing(struct Curl_easy *data, bool *done)
break;
}
Curl_debug(data, CURLINFO_HEADER_IN, (const char *)&mq->firstbyte, 1);
/* we received something */
mq->lastTime = Curl_now();
/* remember the first byte */
mq->npacket = 0;
mqstate(data, MQTT_REMAINING_LENGTH, MQTT_NOSTATE);
@ -794,6 +843,13 @@ static CURLcode mqtt_doing(struct Curl_easy *data, bool *done)
infof(data, "Got DISCONNECT");
*done = TRUE;
}
/* ping response */
if(mq->firstbyte == MQTT_MSG_PINGRESP) {
infof(data, "Received ping response.");
mq->pingsent = FALSE;
mqstate(data, MQTT_FIRST, MQTT_PUBWAIT);
}
break;
case MQTT_CONNACK:
result = mqtt_verify_connack(data);

2
lib/mqtt.h
View file

@ -55,6 +55,8 @@ struct MQTT {
size_t npacket; /* byte counter */
size_t remaining_length;
unsigned char pkt_hd[4]; /* for decoding the arriving packet length */
struct curltime lastTime; /* last time we sent or received data */
bool pingsent; /* 1 while we wait for ping response */
unsigned char firstbyte;
};