move to new skeleton

tutorials/mqtt/mqtt-client/Makefile

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+PROG ?= example                   # Program we are building
+DELETE = rm -rf                   # Command to remove files
+OUT ?= -o $(PROG)                 # Compiler argument for output file
+SOURCES = main.c mongoose.c  packed_fs.c      # Source code files, packed_fs.c contains ca.pem, which contains CA certs for TLS
+CFLAGS = -W -Wall -Wextra -g -I.  # Build options
+
+# Mongoose build options. See https://mongoose.ws/documentation/#build-options
+CFLAGS_MONGOOSE += -DMG_ENABLE_LINES=1 -DMG_ENABLE_PACKED_FS=1
+
+ifeq ($(OS),Windows_NT)   # Windows settings. Assume MinGW compiler. To use VC: make CC=cl CFLAGS=/MD OUT=/Feprog.exe
+  PROG ?= example.exe           # Use .exe suffix for the binary
+  CC = gcc                      # Use MinGW gcc compiler
+  CFLAGS += -lws2_32            # Link against Winsock library
+  DELETE = cmd /C del /Q /F /S  # Command prompt command to delete files
+  OUT ?= -o $(PROG)             # Build output
+  MAKE += WINDOWS=1 CC=$(CC)
+endif
+
+all: $(PROG)              # Default target. Build and run program
+	$(RUN) ./$(PROG) $(ARGS)
+
+$(PROG): $(SOURCES)       # Build program from sources
+	$(CC) $(SOURCES) $(CFLAGS) $(CFLAGS_MONGOOSE) $(CFLAGS_EXTRA) $(OUT)
+
+clean:                    # Cleanup. Delete built program and all build artifacts
+	$(DELETE) $(PROG) *.o *.obj *.exe *.dSYM mbedtls
+
+# see https://mongoose.ws/tutorials/tls/#how-to-build for TLS build options
+
+mbedtls:                  # Pull and build mbedTLS library
+	git clone --depth 1 -b v2.28.2 https://github.com/mbed-tls/mbedtls $@
+	$(MAKE) -C mbedtls/library

tutorials/mqtt/mqtt-client/README.md

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+See detailed tutorial at https://mongoose.ws/tutorials/mqtt/mqtt-client/

tutorials/mqtt/mqtt-client/main.c

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+// Copyright (c) 2023 Cesanta Software Limited
+// All rights reserved
+//
+// Example MQTT client. It performs the following steps:
+//    1. Connects to the MQTT server specified by `s_url` variable
+//    2. When connected, subscribes to the topic `s_sub_topic`
+//    3. Publishes message `hello` to the `s_pub_topic`
+//    4. Receives that message back from the subscribed topic and closes
+//    5. Timer-based reconnection logic revives the connection when it is down
+//
+// To enable SSL/TLS, see https://mongoose.ws/tutorials/tls/#how-to-build
+
+#include "mongoose.h"
+
+static const char *s_url = "mqtt://broker.hivemq.com:1883";
+static const char *s_sub_topic = "mg/+/test";     // Publish topic
+static const char *s_pub_topic = "mg/clnt/test";  // Subscribe topic
+static int s_qos = 1;                             // MQTT QoS
+static struct mg_connection *s_conn;              // Client connection
+
+// Handle interrupts, like Ctrl-C
+static int s_signo;
+static void signal_handler(int signo) {
+  s_signo = signo;
+}
+
+static void fn(struct mg_connection *c, int ev, void *ev_data) {
+  if (ev == MG_EV_OPEN) {
+    MG_INFO(("%lu CREATED", c->id));
+    // c->is_hexdumping = 1;
+  } else if (ev == MG_EV_CONNECT) {
+    if (mg_url_is_ssl(s_url)) {
+      struct mg_tls_opts opts = {.ca = mg_unpacked("/certs/ca.pem"),
+                                 .name = mg_url_host(s_url)};
+      mg_tls_init(c, &opts);
+    }
+  } else if (ev == MG_EV_ERROR) {
+    // On error, log error message
+    MG_ERROR(("%lu ERROR %s", c->id, (char *) ev_data));
+  } else if (ev == MG_EV_MQTT_OPEN) {
+    // MQTT connect is successful
+    struct mg_str subt = mg_str(s_sub_topic);
+    struct mg_str pubt = mg_str(s_pub_topic), data = mg_str("hello");
+    MG_INFO(("%lu CONNECTED to %s", c->id, s_url));
+    struct mg_mqtt_opts sub_opts;
+    memset(&sub_opts, 0, sizeof(sub_opts));
+    sub_opts.topic = subt;
+    sub_opts.qos = s_qos;
+    mg_mqtt_sub(c, &sub_opts);
+    MG_INFO(("%lu SUBSCRIBED to %.*s", c->id, (int) subt.len, subt.buf));
+    struct mg_mqtt_opts pub_opts;
+    memset(&pub_opts, 0, sizeof(pub_opts));
+    pub_opts.topic = pubt;
+    pub_opts.message = data;
+    pub_opts.qos = s_qos, pub_opts.retain = false;
+    mg_mqtt_pub(c, &pub_opts);
+    MG_INFO(("%lu PUBLISHED %.*s -> %.*s", c->id, (int) data.len, data.buf,
+             (int) pubt.len, pubt.buf));
+  } else if (ev == MG_EV_MQTT_MSG) {
+    // When we get echo response, print it
+    struct mg_mqtt_message *mm = (struct mg_mqtt_message *) ev_data;
+    MG_INFO(("%lu RECEIVED %.*s <- %.*s", c->id, (int) mm->data.len,
+             mm->data.buf, (int) mm->topic.len, mm->topic.buf));
+  } else if (ev == MG_EV_CLOSE) {
+    MG_INFO(("%lu CLOSED", c->id));
+    s_conn = NULL;  // Mark that we're closed
+  }
+}
+
+// Timer function - recreate client connection if it is closed
+static void timer_fn(void *arg) {
+  struct mg_mgr *mgr = (struct mg_mgr *) arg;
+  struct mg_mqtt_opts opts = {.clean = true,
+                              .qos = s_qos,
+                              .topic = mg_str(s_pub_topic),
+                              .version = 4,
+                              .message = mg_str("bye")};
+  if (s_conn == NULL) s_conn = mg_mqtt_connect(mgr, s_url, &opts, fn, NULL);
+}
+
+int main(int argc, char *argv[]) {
+  struct mg_mgr mgr;
+  int i;
+
+  // Parse command-line flags
+  for (i = 1; i < argc; i++) {
+    if (strcmp(argv[i], "-u") == 0 && argv[i + 1] != NULL) {
+      s_url = argv[++i];
+    } else if (strcmp(argv[i], "-p") == 0 && argv[i + 1] != NULL) {
+      s_pub_topic = argv[++i];
+    } else if (strcmp(argv[i], "-s") == 0 && argv[i + 1] != NULL) {
+      s_sub_topic = argv[++i];
+    } else if (strcmp(argv[i], "-v") == 0 && argv[i + 1] != NULL) {
+      mg_log_set(atoi(argv[++i]));
+    } else {
+      MG_ERROR(("Unknown option: %s. Usage:", argv[i]));
+      MG_ERROR(
+          ("%s [-u mqtts://SERVER:PORT] [-p PUB_TOPIC] [-s SUB_TOPIC] "
+           "[-v DEBUG_LEVEL]",
+           argv[0], argv[i]));
+      return 1;
+    }
+  }
+
+  signal(SIGINT, signal_handler);   // Setup signal handlers - exist event
+  signal(SIGTERM, signal_handler);  // manager loop on SIGINT and SIGTERM
+
+  mg_mgr_init(&mgr);
+  mg_timer_add(&mgr, 3000, MG_TIMER_REPEAT | MG_TIMER_RUN_NOW, timer_fn, &mgr);
+  while (s_signo == 0) mg_mgr_poll(&mgr, 1000);  // Event loop, 1s timeout
+  mg_mgr_free(&mgr);                             // Finished, cleanup
+
+  return 0;
+}

tutorials/mqtt/mqtt-client/mongoose.c

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

tutorials/mqtt/mqtt-client/mongoose.h

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

tutorials/mqtt/mqtt-client/packed_fs.c

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+../../http/http-client/packed_fs.c