ESP8266 Unreliable TX (occasional "SEND FAIL" message, then stops working)

[AndrewNode]

We're using sdk_v1.4.0_15_09_18 firmware with AT_v0.50 command set on the ESP8266.

When we send data (~100 to 200KB in 2048KB chunks) from the 8266 - many times everything sends correctly, but sometimes (25% of the time), we will be halfway through sending data when the ESP8266 gives a "SEND FAIL" message and just stops working.

Our test is a direct connection to an iPhone (they are sitting physically next to each other), with the ESP8266 acting as the AP.
We have tried various delays between each CIPSEND (100ms, 200ms ,1000ms, 2000ms) - not much difference.
We have also tried reducing the AT+RFPOWER - just wondering if the TX was drawing too much current.
On the packet sniffer I saw a # of retransmissions from the ESP8266 before the SEND FAIL.

Is there a list of the errors that cause SEND FAIL - and how can we reduce the chance of this happening?
How do we re-start transmission upon receiving SEND FAIL from the ESP8266?

[ESP_Faye]

Hi,

There is a parameter <TCP keep alive> when you create a TCP connection by command "AT+CIPSTART".

It can detect if the TCP connection broke unexpectly.

Please set it and have a try, if your problem is still unsolved, please provide the AT logs for debugging.

Thanks for your interest in ESP8266 !

[Alberto]

"There is a parameter <TCP keep alive> when you create a TCP connection by command "AT+CIPSTART". "

This is very interesting! But how to use it? Where can I read on How to use it properly?

Thank you for the answer.

Alberto

[ESP_Faye]

Hi,

Here is the documentation about AT commands: http://bbs.espressif.com/viewtopic.php?f=51&t=1022.

Set the parameter <TCP keep alive> in command "AT+CIPSTART" means that ESP8266 will send packets to detect if the TCP connection broke every XXX time.

Thanks for your interest in ESP8266 !