What's the max size for publish in esp8266 #109

myie9 · 2018-02-04T14:40:03Z

When publish long message as below. It would crash after receive some subscribe.
But it' ok if publish short message. What's the max size for publish in esp8266?

String strConfig = "{"iQiTiYuZhi":" + String(g_iQiTiYuZhi) + ", "iKeepAlertTime":" + String(g_iKeepAlertTime) + ", "iAlertWhenYouRen":" + String(g_iAlertWhenYouRen)
+ ", "YouRenJudgeInterval":" + String(g_YouRenJudgeInterval) + ", "qiTiAlertInterval":" + String(g_qiTiAlertInterval) + ", "iGapAlertPubUpdate":" + String(g_iGapAlertPubUpdate)
+ ", "strPhone":" + g_strPhone + ", "iHideUrl":" + String(g_iHideUrl) + ", "strQQ":" + g_strQQ + ", "iVer":" + String(g_iVer)

flavio-fernandes · 2019-12-24T03:23:34Z

The max size is:

// Largest full packet we're able to send.
// Need to be able to store at least ~90 chars for a connect packet with full
// 23 char client ID.
#define MAXBUFFERSIZE (150)

After spending a long time pulling my hair to understand why I was
hitting a panic when attempting to read from my registered
subscriptions, I found out that the subscriptions member of the
Adafruit_MQTT instance was corrupted. :(

Turns out the memory corruption was caused by my publish
call, where the payload I was providing was bigger than the
allocated space in the buffer for construction of the packet.

Fixes adafruit#109 After spending a long time pulling my hair to understand why I was hitting a panic when attempting to read from my registered subscriptions, I found out that the subscriptions member of the Adafruit_MQTT instance was corrupted. :( Turns out the memory corruption was caused by my publish call, where the payload I was providing was bigger than the allocated space in the buffer for construction of the packet (see buffer[MAXBUFFERSIZE]). To protect myself from ever making this mistake again, I am proposing a simple logic in publishPacket where instead of silently corrupting memory, the code uses as much payload as it can fit in the available space. By seeing the truncated payload, user can decide whether he/she should 1)break it up into different topics, 2) put the payload on a diet, or 3) increase MAXBUFFERSIZE.

Fixes adafruit#109 Fixes adafruit#122 After spending a long time pulling my hair to understand why I was hitting a panic when attempting to read from my registered subscriptions, I found out that the subscriptions member of the Adafruit_MQTT instance was corrupted. :( Turns out the memory corruption was caused by my publish call, where the payload I was providing was bigger than the allocated space in the buffer for construction of the packet (see buffer[MAXBUFFERSIZE]). To protect myself from ever making this mistake again, I am proposing a simple logic in publishPacket where instead of silently corrupting memory, the code uses as much payload as it can fit in the available space. By seeing the truncated payload, user can decide whether he/she should 1)break it up into different topics, 2) put the payload on a diet, or 3) increase MAXBUFFERSIZE.

flavio-fernandes · 2019-12-24T03:39:43Z

@myie9 : Please take a look at #166 and see if that addresses your issue.

Avoid memory corruption from happening when data payload provided in Adafruit_MQTT::publishPacket is greater than MAXBUFFERSIZE. In order to do that, a helper function is being added to calculate how much space is available for the payload after subtracting what is used as header. Pull request adafruit#166 Fixes adafruit#109 Fixes adafruit#122 Signed-off-by: Flavio Fernandes <flavio@flaviof.com>

Avoid memory corruption from happening when data payload provided in Adafruit_MQTT::publishPacket is greater than MAXBUFFERSIZE. In order to do that, a helper function is being added to calculate how much space is available for the payload after subtracting what is used as the header. Pull request adafruit#166 Fixes adafruit#109 Fixes adafruit#122 Signed-off-by: Flavio Fernandes <flavio@flaviof.com>

flavio-fernandes mentioned this issue Dec 24, 2019

Adafruit_MQTT::publishPacket: Protect against memory corruption. #166

Merged

brentru closed this as completed in #166 May 14, 2021

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What's the max size for publish in esp8266 #109

What's the max size for publish in esp8266 #109

myie9 commented Feb 4, 2018

flavio-fernandes commented Dec 24, 2019 •

edited

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flavio-fernandes commented Dec 24, 2019

What's the max size for publish in esp8266 #109

What's the max size for publish in esp8266 #109

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myie9 commented Feb 4, 2018

flavio-fernandes commented Dec 24, 2019 • edited Loading

flavio-fernandes commented Dec 24, 2019

flavio-fernandes commented Dec 24, 2019 •

edited

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