Post request looks like 2 different requests on ESP8266. Is this a Chrome bug?

Question

I am setting up a server on ESP8266 WiFi module. Basic operation is, you request a URL. ESP serves that page. It has a form. You fill it in and click submit, and the browser sends POST request by AJAX. I am not using jQuery, just js. From Chrome dev-tools, it looks like all is well.

But on the ESP Server side, I noticed I am missing post data once in a while. After digging deep, I found this issue.

Ideal result from Chrome on my windows: And this works correctly. Post data comes in as expected.

+IPD,0,507:POST /wifi.htm HTTP/1.1
Host: 192.168.4.1
Connection: keep-alive
Content-Length: 63
Origin: http://192.168.4.1
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36
Content-Type: text/plain;charset=UTF-8
Accept: */*
Referer: http://192.168.4.1/wifi.htm
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8
AlexaToolbar-ALX_NS_PH: AlexaToolbar/alx-4.0

ethOrWiFi=1&ewln=1&dhcp=1&ssid=Esensors&key=tgfgfdgfdtrd&auth=4

But on my Mac Chrome, I see the following result.

+IPD,0,472:POST /wifi.htm HTTP/1.1
Host: 192.168.4.1
Connection: keep-alive
Content-Length: 63
Origin: http://192.168.4.1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36
Content-Type: text/plain;charset=UTF-8
Accept: */*
DNT: 1
Referer: http://192.168.4.1/wifi.htm
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8,ml;q=0.6
AlexaToolbar-ALX_NS_PH: AlexaToolbar/alx-4.0

+IPD,0,63:ethOrWiFi=1&ewln=1&dhcp=1&ssid=Esensors&key=asdfasdfasdf&auth=4

And I can repeat this. The only different in each case is I am using Chrome on Windows as opposed to Chrome on Mac. To double check, I downloaded Chrome canary version and tried. The first request worked fine. From second request onwards, it shows this problem. Why is this happening? Any ideas? May be my laptop has issues? :)

Here are Chrome dev-tools info from Chrome on Mac (the one with the problem)

**Request Headers:**
POST /wifi.htm HTTP/1.1
Host: 192.168.4.1
Connection: keep-alive
Content-Length: 61
Origin: http://192.168.4.1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36
Content-Type: text/plain;charset=UTF-8
Accept: */*
DNT: 1
Referer: http://192.168.4.1/wifi.htm
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8,ml;q=0.6
AlexaToolbar-ALX_NS_PH: AlexaToolbar/alx-4.0
**Request Payload**
ethOrWiFi=1&ewln=1&dhcp=1&ssid=Esensors&key=asdfasdfoi&auth=4

Answer 1

+IPD is the AT command that says data was received from the network. +IPD,0,63: is saying to receive 63 bytes from connection 0. That matches with your Content-Length header. Notice that it also appears at the beginning of the header portion of the request.

Your WiFi library on the ESP side is throwing that in. Here and on line 281 is the source code where it might be happening. There are a couple variables that affect whether or not the +IPD is added, maybe you have set or inadvertently changed one.