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martin-ger / esp_mqtt

MQTT Broker/Bridge on the ESP8266
MIT License
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arduino esp8266 mqtt-bridge mqtt-broker

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esp_uMQTT_broker

An MQTT Broker/Client with scripting support on the ESP8266

This program enables the ESP8266 to become the central node in a small distributed IoT system. It implements an MQTT Broker and a simple scripted rule engine with event/action statements that links together the MQTT sensors and actors. It can act as STA, as AP, or as both and it can connect to another MQTT broker (i.e. in the cloud). Here it can also be bridge that forwards and rewrites topics in both directions. Also it can parse JSON structures, send basic HTTP GET requests and do basic I/O: i.e. read and write to local GPIO pins, react on timers and GPIO interrupts, drive GPIO pins with PWM, and read the ADC.

Find a video that explains the ideas and the architecture of the project at: https://www.youtube.com/watch?v=0K9q4IuB_oA

You can use the pure broker functionality (not the CLI and the scripting) in any ESP Arduino project as a libary by going to https://github.com/martin-ger/uMQTTBroker . Just clone (or download the zip-file and extract it) into the libraries directory of your Arduino ESP8266 installation.

Usage

In the user directory there is the main program that serves as a stand-alone MQTT broker, client and bridge. The program starts with the following default configuration:

This means it starts an open AP with ap_ssid MyAP. This default can be changed in the file user_config.h. The default can be overwritten and persistenly saved to flash by using a console interface. This console is available either via the serial port at 115200 baud or via tcp port 7777 (e.g. "telnet 192.168.4.1 7777" from a connected STA). It does not yet try to automatically re-connect to an uplink AP (as it does not know a valid ssid or password).

Use the following commands for an initial setup:

After reboot it will try to automatically connect to your home router and itself as AP is ready for stations to connect.

The console understands the following commands:

General commands:

WiFi and network related commands:

While the user interface looks similar to my esp_wifi_repeater at https://github.com/martin-ger/esp_wifi_repeater this does NO NAT routing. AP and STA network are stricly separated and there is no routing in between. The only possible connection via both networks is the uMQTT broker that listens on both interfaces.

MQTT broker related command:

MQTT client/bridging functionality

The broker comes with a "local" and a "remote" client, which means, the broker itself can publish and subscribe topics. The "local" client is a client to the own broker (without the need of an additional TCP connection).

By default the "remote" MQTT client is disabled. It can be enabled by setting the config parameter "mqtt_host" to a hostname different from "none". To configure the "remote" MQTT client you can set the following parameters:

The remote MQTT server can be accessed via SSL, e.g. a secure test connection to test.mosquitto.org can be configured as following:

CMD>set mqtt_host test.mosquitto.org
CMD>set mqtt_port 8883
CMD>set mqtt_ssl 1
CMD>save
CMD>reset

Certificate checks are not yet implemented.

Scripting

The esp_uMQTT_broker comes with a build-in scripting engine. A script enables the ESP not just to act as a passive broker but to react on events (publications and timing events), to send out its own items and handle local I/O. Details on syntax and semantics of the scripting language can be found here: https://github.com/martin-ger/esp_mqtt/blob/master/SCRIPTING.md . Examples of scripts are in the "scripts" directory.

The script specific CLI commands are:

Debug commands:

The backlog buffer stores the most recent console outputs of the running script and the CLI. If you detect an error situation you can log into the remote console and dump the recent output with "show backlog".

Scripts with size up to 4KB are uploaded to the esp_uMQTT_broker using a network interface.

There are two options to upload a script:

Script Pull (http)

For this, you first have to make the scripts available via a web server. A quite simple way to do that is to start a minimal web server in the "scripts" directory, i.g. on Linux you can start a server on port 8080 on the delevopment machine with:

$ cd scripts
python -m SimpleHTTPServer 8080

Another way of course is to upload the script to a real server somewhere on the web.

Then start the download with the command "script " on the concole of the ESP, e.g. like this with the correct hostname and port:

CMD>script http://myserver:8080/scripts/script.new
HTTP request to myserver:8080/scripts/script.new started
HTTP script download completed (330 Bytes)
Syntax okay
CMD>

You can also download over the internet, e.g. directly from github:

CMD>script https://raw.githubusercontent.com/martin-ger/esp_mqtt/master/scripts/script.pwm
HTTP request to https://raw.githubusercontent.com/martin-ger/esp_mqtt/master/scripts/script.pwm started
HTTP script download completed (749 Bytes)
Syntax okay
CMD>

The ESP tries to download the script from the given URL and prints upon success or failure a report on the console.

Script Push (netcat)

Another option is to upload the script as plain TCP stream. Start the upload with "script " on the console of the ESP, e.g.:

CMD>script 2000
Waiting for script upload on port 2000
CMD>

Now the ESP listens on the given port for an incoming connection and stores anything it receives as new script. Upload a file using netcat, e.g.:

$ netcat 192.168.178.29 2000 < user/demo_script2

The ESP will store the file and immediatly checks the syntax of the script:

CMD>script 2000
Waiting for script upload on port 2000
Script upload completed (451 Bytes)
Syntax okay
CMD>

You can examine the currently loaded script using the "show script" command. It only displays about 1KB of a script. If you need to see more, use "show script " with a higher starting line. Newly loaded scripts are stored persistently in flash and will be executed after next reset if they contain no syntax errors. "script delete" stops script execution and deleted a script from flash.

NTP Support

NTP time is supported and accurate timestamps are available if the sync with an NTP server is done. By default the NTP client is enabled and set to "1.pool.ntp.org". It can be changed by setting the config parameter "ntp_server" to a hostname or an IP address. An ntp_server of "none" will disable the NTP client. Also you can set the "ntp_timezone" to an offset from GMT in hours. The system time will be synced with the NTP server every "ntp_interval" seconds. Here it uses NOT the full NTP calculation and clock drift compensation. Instead it will just set the local time to the latest received time.

After NTP sync has been completed successfully once, the local time will be published every second under the topic "$SYS/broker/time" in the format "hh:mm:ss". You can also query the NTP time using the "time" command from the commandline.

If you don't have internet access but still need a time base e.g. for your script, you can set the time manually (be aware that the local timer of the ESP has a significant drift):

DNS

A simple DNS responder is included, so an MQTT client connected to the AP interface might also use a name instead of the IP. Any valid domain name can be configured (shorter than 31 chars).

mDNS

mDNS is supported and depending on "mdns_mode" the broker responds on the name "mqtt.local" with one of its two addresses:

Building and Flashing

The code can be used in any project that is compiled using the NONOS_SDK or the esp-open-sdk. Also the complete broker in the user directory can be build using the standard SDKs after adapting the variables in the Makefile.

Download the repository using

$ git clone --recursive  https://github.com/martin-ger/esp_mqtt.git

Configure the build options in "user_config.h", then build the esp_uMQTT_broker firmware with "make". "make flash" flashes it onto an esp8266.

If you want to use the precompiled binaries from the firmware directory you can flash them directly on an ESP8266, e.g. with

$ esptool.py --port /dev/ttyUSB0 write_flash -fs 32m 0x00000 firmware/0x00000.bin 0x10000 firmware/0x10000.bin

On Windows you can flash it using the "ESP8266 Download Tool" available at https://espressif.com/en/support/download/other-tools. Download the two files 0x00000.bin and 0x10000.bin from the firmware directory. For a generic ESP12, a NodeMCU or a Wemos D1 use the following settings (for an ESP-01 change FLASH SIZE to "8Mbit"):

Known Issues

If "QIO" mode fails on your device, try "DIO" instead. Also have a look at the "Detected Info" to check size and mode of the flash chip. If your downloaded firmware still doesn't start properly, please check with the enclosed checksums whether the binary files are possibly corrupted.

The MQTT broker library

The library code has been moved to a separate repository at https://github.com/martin-ger/uMQTTBroker and is included recursivly.

It can be integrated into any NONOS SDK (or esp-open-sdk) program ("make -f Makefile.orig lib" will build the mqtt code as a C library). You can find a minimal NONOS SDK sample in the directory "user_basic" in this repository. Rename it to "user", adapt "user_config.h", and do the "make" to build a small demo that just starts an MQTT broker without any additional logic.

The broker is started by simply including:

#include "mqtt/mqtt_server.h"

and then calling

bool MQTT_server_start(uint16_t portno, uint16_t max_subscriptions, uint16_t max_retained_topics);

in the "user_init()" (or Arduino "setup()") function. Now it is ready for MQTT connections on all activated interfaces (STA and/or AP). Please note, that the lib uses two tasks (with prio 1 and 2) for client and broker. Thus, only task with prio 0 is left for a user application.

Limitations on the number of clients

To adjust memory consumption of one MQTT connection and thus the max number of concurrent connections you can redefine MQTT_BUF_SIZE and QUEUE_BUFFER_SIZE in "user_config.h". MQTT_BUF_SIZE is the max. size of pending inbound messages for one connection (and thus also the max. size of a single MQTT message) and QUEUE_BUFFER_SIZE is the max. size of all pending outbound messages for one connection. Currently these parameters are set to 1024 resp. 2048 bytes, resulting in a memory consumption of about 4 KB per connection and a max number of connections of about 8-9 (depending on the memory usage of the rest of the program). When you reduce buffer sizes, e.g. to 512 and 1024 bytes, a single connection requires only about 2.5 KB resulting in up to 13 possible concurrent MQTT connections. In any case you have to increase the number of TCP connections (default 5) first by calling "espconn_tcp_set_max_con(n)" with n, the max. number of concurrent TCP connections, less or equal to 15.

Also there is a hard limitation on the number of STAs connected to the SoftAP, which is 8. I.e. when using the esp_uMQTT_broker only with clients via the SoftAP interface, even with reduced memory consumtion, the limit of different client nodes is still 8, as it is imposed by the binary WiFi driver. Only when used via the STA interface and an external AP you can connect more than 8 MQTT clients.

Thanks