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I would like to host a web page from a RPi that has websocket controls that update in 'real time' such as a slider that transmits its value as you move it. I then want to broadcast the values to several ESP8266 modules (~10) running Arduino via Wi-Fi. I would like to have a payload data rate of ~10 bytes/packet x 30Hz = 300 Bytes/s.

What type of connection should I use for the Pi to the ESP8266s? I think MQTT is too slow for this?

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    Why do you think a protocol and not say the quality of the network, or the ESP8266 ability to decode the protocol will be too slow?
    – hardillb
    May 16, 2018 at 7:52
  • Network speed has nothing to do with processor clock speed, other than how fast it can send data to the network chip/card. Your limiting factor w.r.t. your network is more about transfer rate and how congested your network might be (and therefor cause collisions/re-transmits.) A quick Google search for ESP8266 WIFI Speed shows several folks getting transfer rates into the MegaBits per Second (mbps) range. 1040 mbps (10 ESP8266's x (10 bytes/packet payload + 3 bytes MQTT overhead) x 8-bits) seems easily do-able on a 2.4Ghz Wifi "G" or "N" network.
    – JD Allen
    May 16, 2018 at 14:04
  • ESP8266's run at 80MHz....no CPU has ran at 30Hz since the 1960's :)
    – JD Allen
    May 16, 2018 at 14:05

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MQTT should be more than fast enough for your architecture, given a decent WiFi network. I run about 30 sensors (ESP8266, Feather MO, Arduino Uno, etc.) all using MQTT back to a Mosquitto Broker running as a Docker Container on an 15yo laptop, which connects back out to my control software and displays, and it all works just fine. I'm pushing close to 2 million MQTT packets a day at my house...so your 864k seems do-able to me :)

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  • Thanks. I am concerned because MQTT services such as AdafruitIO or Sparkfun were advertising one message per second rate limits.
    – user6397
    May 17, 2018 at 12:05
  • @user6397: Both of those services throttle their traffic to prevent people from swamping them. If you run a local MQTT Broker like Mosquitto or Mosca, you won't have those limits. I use AT&T's M2M service myself, but I have to do my own throttling with Node-RED and just send them a 1 minute average of some sensor data that comes in every 3 seconds to my MQTT broker....otherwise I would go over my monthly free limit very quickly!
    – JD Allen
    May 17, 2018 at 13:33

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