Glad you got this improved! I'm not sure how much room for improvement there is here - I just checked and it seems that the WiFi stack should be able to send data out in ~530 byte chunks, so it should mean data from the file goes straight out.
Without digging down (you could attach a USB-TTL converter to the ESP8266 RX line and look at what's being sent and when) it's hard to know where the slowdown might be.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Glad you got this improved! I'm not sure how much room for improvement there is here - I just checked and it seems that the WiFi stack should be able to send data out in ~530 byte chunks, so it should mean data from the file goes straight out.
Without digging down (you could attach a USB-TTL converter to the ESP8266 RX line and look at what's being sent and when) it's hard to know where the slowdown might be.