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Add OTA over mqtt example
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‎tutorials/mqtt/ota-over-mqtt/Makefile‎

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PROG ?= example # Program we are building
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DELETE = rm -rf # Command to remove files
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OUT ?= -o $(PROG) # Compiler argument for output file
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SOURCES = main.c mongoose.c # Source code files, packed_fs.c contains ca.pem, which contains CA certs for TLS
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CFLAGS = -W -Wall -Wextra -g -I. # Build options
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# Mongoose build options. See https://mongoose.ws/documentation/#build-options
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CFLAGS_MONGOOSE += -DMG_ENABLE_LINES=1
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CFLAGS_MONGOOSE += -DMG_TLS=MG_TLS_BUILTIN
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#CFLAGS_MONGOOSE += -DMG_TLS=MG_TLS_OPENSSL -L/opt/homebrew/opt/openssl/lib -I/opt/homebrew/opt/openssl/include -lssl -lcrypto
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#CFLAGS_MONGOOSE += -DMG_TLS=MG_TLS_MBED -L/opt/homebrew/opt/mbedtls/lib -I/opt/homebrew/opt/mbedtls/include -lmbedtls -lmbedcrypto -lmbedx509
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ifeq ($(OS),Windows_NT) # Windows settings. Assume MinGW compiler. To use VC: make CC=cl CFLAGS=/MD OUT=/Feprog.exe
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PROG ?= example.exe # Use .exe suffix for the binary
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CC = gcc # Use MinGW gcc compiler
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CFLAGS += -lws2_32 # Link against Winsock library
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DELETE = cmd /C del /Q /F /S # Command prompt command to delete files
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OUT ?= -o $(PROG) # Build output
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endif
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all: $(PROG) # Default target. Build and run program
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$(RUN) ./$(PROG) $(ARGS)
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$(PROG): $(SOURCES) # Build program from sources
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$(CC) $(SOURCES) $(CFLAGS) $(CFLAGS_MONGOOSE) $(CFLAGS_EXTRA) $(OUT)
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clean: # Cleanup. Delete built program and all build artifacts
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$(DELETE) $(PROG) *.o *.obj *.exe *.dSYM

‎tutorials/mqtt/ota-over-mqtt/main.c‎

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// Copyright (c) 2013-2026 Cesanta Software Limited
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// All rights reserved
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//
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// This example implements a JSON-RPC server that connects to the MQTT server
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// and expects requests on MQTT_RX_TOPIC, and sends responses to the
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// MQTT_TX_TOPIC. Only a single RPC method is implemented, "ota.update",
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// which expects parameters {"total": XX, "offset": XX, "chunk": "..."}
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// The rpc_ota_update() function handles those requests and calls Mongoose
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// ota_begin(), ota_write(), ota_end() respectively.
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//
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// Visit https://mongoose.ws/mqtt/ web page to push the firmware binary.
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#include "mongoose.h"
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#define MQTT_SERVER_URL "mqtt://broker.hivemq.com:1883"
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#define MQTT_RX_TOPIC "mg/123/rx"
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#define MQTT_TX_TOPIC "mg/123/tx"
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static uint8_t s_qos = 1; // MQTT QoS
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static struct mg_connection *s_conn; // MQTT Client connection
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static struct mg_rpc *s_rpc = NULL; // List of registered RPC methods
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static void rpc_ota_update(struct mg_rpc_req *r) {
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long ofs = mg_json_get_long(r->frame, "$.params.offset", -1);
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long tot = mg_json_get_long(r->frame, "$.params.total", -1);
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int len = 0;
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char *buf = mg_json_get_b64(r->frame, "$.params.chunk", &len);
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if (buf == NULL) {
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mg_rpc_err(r, 1, "%m", MG_ESC("Chunk decoding error"));
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} else if (ofs < 0 || tot < 0) {
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mg_rpc_err(r, 1, "%m", MG_ESC("offset and total not set"));
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} else if (ofs == 0 && mg_ota_begin((size_t) tot) == false) {
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mg_rpc_err(r, 1, "\"mg_ota_begin(%ld) failed\"", tot);
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} else if (len > 0 && mg_ota_write(buf, len) == false) {
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mg_rpc_err(r, 1, "\"mg_ota_write(%lu) @%ld failed\"", len, ofs);
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mg_ota_end();
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} else if (len == 0 && mg_ota_end() == false) {
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mg_rpc_err(r, 1, "\"mg_ota_end() failed\"", tot);
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} else {
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mg_rpc_ok(r, "%m", MG_ESC("ok"));
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}
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mg_free(buf);
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}
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static void subscribe(struct mg_connection *c, struct mg_str topic) {
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struct mg_mqtt_opts opts = {};
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memset(&opts, 0, sizeof(opts));
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opts.topic = topic;
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opts.qos = s_qos;
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mg_mqtt_sub(c, &opts);
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MG_INFO(("%lu SUBSCRIBED to %.*s", c->id, topic.len, topic.buf));
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}
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static void publish(struct mg_connection *c, struct mg_str topic,
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struct mg_str message) {
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struct mg_mqtt_opts opts = {};
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memset(&opts, 0, sizeof(opts));
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opts.topic = topic;
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opts.message = message;
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opts.qos = s_qos;
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mg_mqtt_pub(c, &opts);
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MG_INFO(("%lu PUBLISHED %.*s -> %.*s", c->id, topic.len, topic.buf,
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message.len, message.buf));
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}
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static void ev_handler(struct mg_connection *c, int ev, void *ev_data) {
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if (ev == MG_EV_OPEN) {
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MG_INFO(("%lu CREATED", c->id));
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// c->is_hexdumping = 1;
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} else if (ev == MG_EV_CONNECT) {
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MG_INFO(("Connected"));
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} else if (ev == MG_EV_ERROR) {
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// On error, log error message
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MG_ERROR(("%lu ERROR %s", c->id, (char *) ev_data));
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} else if (ev == MG_EV_MQTT_OPEN) {
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// MQTT connect is successful
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MG_INFO(("%lu CONNECTED", c->id));
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subscribe(c, mg_str(MQTT_RX_TOPIC));
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} else if (ev == MG_EV_MQTT_MSG) {
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// When we get echo response, print it
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struct mg_mqtt_message *mm = (struct mg_mqtt_message *) ev_data;
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struct mg_iobuf io = {0, 0, 0, 512};
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struct mg_rpc_req r = {&s_rpc, NULL, mg_pfn_iobuf,
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&io, NULL, {mm->data.buf, mm->data.len}};
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size_t clipped_len = mm->data.len > 512 ? 512 : mm->data.len;
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MG_INFO(("%lu RECEIVED %.*s <- %.*s", c->id, clipped_len, mm->data.buf,
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mm->topic.len, mm->topic.buf));
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mg_rpc_process(&r);
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if (io.buf != NULL && io.len > 0) {
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publish(c, mg_str(MQTT_TX_TOPIC), mg_str_n((char *) io.buf, io.len));
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}
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mg_iobuf_free(&io);
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} else if (ev == MG_EV_CLOSE) {
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MG_INFO(("%lu CLOSED", c->id));
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s_conn = NULL; // Mark that we're closed
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}
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}
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static void timer_sntp(void *param) { // SNTP timer function. Sync up time
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static uint64_t hourly_timer = 0;
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uint64_t t1 = mg_now(), t2 = mg_millis();
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if (t1 < t2 + 3600 || mg_timer_expired(&hourly_timer, 3600000, t2)) {
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mg_sntp_connect(param, "udp://time.google.com:123", NULL, NULL);
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}
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}
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static void timer_fn(void *arg) {
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if (s_conn == NULL) {
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struct mg_mgr *mgr = (struct mg_mgr *) arg;
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struct mg_mqtt_opts opts = {.clean = true,
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.qos = s_qos,
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.topic = mg_str(MQTT_TX_TOPIC),
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.keepalive = 5,
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.version = 4,
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.message = mg_str("{\"method\":\"bye\"}")};
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s_conn = mg_mqtt_connect(mgr, MQTT_SERVER_URL, &opts, ev_handler, NULL);
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} else {
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mg_mqtt_ping(s_conn);
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}
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}
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int main(void) {
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struct mg_mgr mgr;
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mg_log_set(MG_LL_INFO);
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mg_mgr_init(&mgr);
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mg_timer_add(&mgr, 3000, MG_TIMER_REPEAT | MG_TIMER_RUN_NOW, timer_fn, &mgr);
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mg_timer_add(&mgr, 100, MG_TIMER_REPEAT, timer_sntp, &mgr);
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mg_rpc_add(&s_rpc, mg_str("ota.update"), rpc_ota_update, NULL);
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for (;;) mg_mgr_poll(&mgr, 100);
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mg_mgr_free(&mgr);
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return 0;
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}

‎tutorials/mqtt/ota-over-mqtt/mongoose.c‎

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../../../mongoose.c

‎tutorials/mqtt/ota-over-mqtt/mongoose.h‎

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../../../mongoose.h

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