Add Sparkplug B Industrial IoT Example by embhorn · Pull Request #461 · wolfSSL/wolfMQTT

embhorn · 2026-02-05T21:39:17Z

Add Sparkplug B Industrial IoT Example

Summary

This PR adds a new example demonstrating the https://sparkplug.eclipse.org/
industrial IoT protocol specification using wolfMQTT. The example creates two
MQTT clients that communicate using the Sparkplug topic namespace and message
types.

Changes

New example: examples/sparkplug/sparkplug.c and sparkplug.h
Documentation: examples/sparkplug/README.md
Build integration for Autotools (examples/include.am) and CMake
(CMakeLists.txt)
Added Sparkplug section to main README.md

Features

Two Communicating Clients:

Edge Node: Publishes sensor data and responds to commands
Host Application: Subscribes to data and sends commands (requires
--enable-mt)

Sparkplug Protocol Support:

Topic namespace:
spBv1.0/{group_id}/{message_type}/{edge_node_id}[/{device_id}]
Message types: NBIRTH, NDEATH, DDATA, DCMD
Birth/Death sequence tracking
Last Will and Testament (NDEATH) for unexpected disconnects
Simplified payload encoding (demonstrates concepts without requiring
protobuf dependency)

Simulated Metrics:

Temperature (float)
Humidity (float)
LED state (boolean, controllable via command)
Counter (uint32)

Build & Test

Autotools - single-threaded (Edge Node only)

./configure --disable-tls
make

Autotools - multi-threaded (both clients)

./configure --enable-mt --disable-tls
make

CMake - multi-threaded

mkdir build && cd build
cmake -DWOLFMQTT_TLS=no -DWOLFMQTT_MT=yes ..
make sparkplug

Run

./examples/sparkplug/sparkplug -h test.mosquitto.org -p 1883

Example Output

Sparkplug B Example

Starting Edge Node and Host Application threads...

Sparkplug: Connected! (client_id=WolfMQTT_Sparkplug_Edge)
Sparkplug: Published NBIRTH to spBv1.0/WolfMQTT/NBIRTH/EdgeNode1

Sparkplug [WolfMQTT_Sparkplug_Host]: Received NBIRTH from WolfMQTT/EdgeNode1
-> Edge Node came online (bdSeq=0)

Sparkplug: Published DDATA to spBv1.0/WolfMQTT/DDATA/EdgeNode1/Device1
Sparkplug [WolfMQTT_Sparkplug_Host]: Received DDATA from
WolfMQTT/EdgeNode1/Device1
-> Device data received:
Temperature = 22.83
Humidity = 45.36
LED = OFF

Sparkplug [Host]: Sending DCMD to spBv1.0/WolfMQTT/DCMD/EdgeNode1/Device1
(LED=ON)
Sparkplug [WolfMQTT_Sparkplug_Edge]: Received DCMD from
WolfMQTT/EdgeNode1/Device1
-> Command received:
LED set to ON

Sparkplug example completed!

Test Plan

Builds with ./configure --disable-tls (single-threaded)
Builds with ./configure --enable-mt --disable-tls (multi-threaded)
Builds with CMake (-DWOLFMQTT_TLS=no -DWOLFMQTT_MT=yes)
Runs successfully against test.mosquitto.org
Edge Node publishes NBIRTH and DDATA messages
Host Application receives messages and sends DCMD
Edge Node receives and processes commands
Clean disconnect for both clients

New example demonstrating the Sparkplug B industrial IoT protocol: - Edge Node client publishes sensor data and responds to commands - Host Application client subscribes to data and sends commands - Implements Sparkplug topic namespace (spBv1.0/{group}/{type}/{node}[/{device}]) - Demonstrates NBIRTH, NDEATH, DDATA, and DCMD message types - Includes simplified payload encoding (not full protobuf) - Supports both single-threaded and multi-threaded builds Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README covers: - Protocol overview and architecture - Message types and simulated metrics - Build instructions (Autotools and CMake) - Command-line options and example output - Configuration and payload format notes Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Link to examples/sparkplug/README.md for detailed documentation. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Use WOLF_CRYPT_TYPES_H include guard to skip the word64 typedef when wolfSSL has already defined it, matching the pattern used in wolfmqtt/mqtt_types.h. Fixes build error on macOS where wolfSSL defines word64 as unsigned long vs uint64_t (unsigned long long). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Copilot

Pull request overview

This PR adds a new Sparkplug B Industrial IoT example to wolfMQTT, demonstrating Sparkplug-style topic namespaces and message flows using two MQTT clients (Edge Node + Host Application), plus build-system and documentation integration.

Changes:

Added new Sparkplug example implementation (examples/sparkplug/sparkplug.c/.h) with simplified (non-protobuf) payload encoding/decoding.
Integrated the new example into Autotools and CMake builds, and updated .gitignore.
Added user documentation for the example and linked it from the project README.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
examples/sparkplug/sparkplug.h	Defines Sparkplug message/topic helpers and simplified payload encode/decode utilities.
examples/sparkplug/sparkplug.c	Implements the Edge Node + Host example clients, message callback handling, and publish/subscribe loops.
examples/sparkplug/README.md	Documents Sparkplug concepts, build/run instructions, and example output.
examples/include.am	Adds the new example to Autotools build targets and distribution lists.
README.md	Adds a top-level section pointing users to the Sparkplug example.
CMakeLists.txt	Registers the Sparkplug example target under `WOLFMQTT_EXAMPLES`.
.gitignore	Ignores the built Sparkplug example binary.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Copilot · 2026-02-06T15:56:20Z

examples/sparkplug/sparkplug.h

+static INLINE int SparkplugTopic_Build(char* buf, int buf_len,
+    const char* group_id, SparkplugMsgType msg_type,
+    const char* edge_node_id, const char* device_id)
+{
+    int len;
+    const char* type_str = SparkplugMsgType_ToString(msg_type);
+
+    if (device_id != NULL) {
+        len = XSNPRINTF(buf, buf_len, "%s/%s/%s/%s/%s",
+            SPARKPLUG_NAMESPACE, group_id, type_str, edge_node_id, device_id);
+    }
+    else {
+        len = XSNPRINTF(buf, buf_len, "%s/%s/%s/%s",
+            SPARKPLUG_NAMESPACE, group_id, type_str, edge_node_id);
+    }
+
+    return len;
+}


SparkplugTopic_Build returns the XSNPRINTF result, but callers don’t check for truncation (return >= buf_len) or errors (negative). If the topic is truncated, publishes/subscribes can silently target the wrong topic. Consider returning an error code on truncation and checking the return value at call sites.

Copilot · 2026-02-06T15:56:20Z

examples/sparkplug/sparkplug.h

+    /* Encode each metric */
+    for (i = 0; i < payload->metric_count; i++) {
+        const SparkplugMetric* m = &payload->metrics[i];
+
+        /* Name length and name */
+        name_len = (word16)XSTRLEN(m->name);
+        if (pos + 2 + name_len + 17 > buf_len) {
+            return MQTT_CODE_ERROR_OUT_OF_BUFFER;
+        }


SparkplugPayload_Encode trusts payload->metric_count and iterates that many metrics without bounding it to SPARKPLUG_MAX_METRICS. If a caller sets a larger count, this will read past the metrics array. Clamp/validate metric_count up-front and return BAD_ARG when out of range.

Copilot · 2026-02-06T15:56:21Z

examples/sparkplug/sparkplug.h

+    /* Decode each metric */
+    for (i = 0; i < payload->metric_count && pos < buf_len; i++) {
+        SparkplugMetric* m = &payload->metrics[i];
+
+        /* Name length and name */
+        if (pos + 2 > buf_len) break;
+        name_len = ((word16)buf[pos] << 8) | buf[pos+1];
+        pos += 2;
+        if (pos + name_len > buf_len || name_len >= sizeof(name_bufs[0])) break;
+        XMEMCPY(name_bufs[i], &buf[pos], name_len);


SparkplugPayload_Decode can break out of the metric loop on malformed/truncated input, but it does not update payload->metric_count to the number of successfully decoded metrics. Callers then iterate payload.metric_count and may dereference NULL m->name / uninitialized metrics, leading to crashes (e.g., XSTRCMP(m->name, ...)). Update metric_count to i on early exit and consider returning MQTT_CODE_ERROR_MALFORMED_DATA when decoding fails.

Copilot · 2026-02-06T15:56:21Z

examples/sparkplug/sparkplug.c

+    MQTTCtx* mqttCtx = &spCtx->mqttCtx;
+    static MqttTopic topics[1];
+
+    XMEMSET(&mqttCtx->subscribe, 0, sizeof(mqttCtx->subscribe));
+    mqttCtx->subscribe.packet_id = mqtt_get_packetid();
+    mqttCtx->subscribe.topic_count = 1;
+    topics[0].topic_filter = topic_filter;
+    topics[0].qos = mqttCtx->qos;
+    mqttCtx->subscribe.topics = topics;
+


sparkplug_subscribe uses a static MqttTopic topics[1], which is shared across threads. In multi-thread mode the edge and host threads can call subscribe concurrently, causing races/corruption of the subscribe request. Use a stack MqttTopic (or mqttCtx->topics like other examples) instead of a static shared array.

Copilot · 2026-02-06T15:56:21Z

examples/sparkplug/sparkplug.c

+    if (msg_new) {
+        /* Parse topic */
+        char topic_str[SPARKPLUG_TOPIC_MAX_LEN];
+        int topic_len = msg->topic_name_len;
+        if (topic_len >= (int)sizeof(topic_str)) {
+            topic_len = sizeof(topic_str) - 1;
+        }
+        XMEMCPY(topic_str, msg->topic_name, topic_len);
+        topic_str[topic_len] = '\0';
+
+        rc = SparkplugTopic_Parse(topic_str, group_id, sizeof(group_id),
+                                  &msg_type, node_id, sizeof(node_id),
+                                  device_id, sizeof(device_id));
+
+        if (rc == MQTT_CODE_SUCCESS) {
+            PRINTF("Sparkplug [%s]: Received %s from %s/%s%s%s",
+                   spCtx->mqttCtx.client_id,
+                   SparkplugMsgType_ToString(msg_type),
+                   group_id, node_id,
+                   device_id[0] ? "/" : "", device_id);
+
+            /* Decode payload if complete */
+            if (msg_done && msg->buffer_len > 0) {
+                rc = SparkplugPayload_Decode(msg->buffer, msg->buffer_len, &payload);
+                if (rc > 0) {
+#ifdef SPARKPLUG_DEBUG


mqtt_message_cb only processes messages inside if (msg_new) { ... }, but wolfMQTT can invoke the callback multiple times per PUBLISH (msg_new=1 first chunk, then msg_new=0 for subsequent chunks, with msg_done=1 on the final chunk). With the current structure, multi-chunk payloads will never be decoded/handled because the msg_done path is skipped when msg_new==0. Consider caching the parsed topic/msg_type on msg_new and performing decode/handling when msg_done is true (even if msg_new is false), or accumulate payload until complete.

Copilot · 2026-02-06T15:56:22Z

examples/sparkplug/sparkplug.c

+    /* Cleanup */
+    MqttClientNet_DeInit(&mqttCtx->net);
+
+    if (mqttCtx->tx_buf) {
+        WOLFMQTT_FREE(mqttCtx->tx_buf);
+        mqttCtx->tx_buf = NULL;
+    }
+    if (mqttCtx->rx_buf) {
+        WOLFMQTT_FREE(mqttCtx->rx_buf);
+        mqttCtx->rx_buf = NULL;
+    }
+
+    PRINTF("Sparkplug: Disconnected %s", mqttCtx->client_id);
+    return rc;


sparkplug_disconnect frees buffers and deinitializes the network, but it never calls MqttClient_DeInit(&mqttCtx->client). In multi-thread builds MqttClient_Init allocates/initializes semaphores inside the client, so skipping MqttClient_DeInit can leak OS resources. Call MqttClient_DeInit during disconnect (and on connect/init error paths).

Copilot · 2026-02-06T15:56:22Z

examples/sparkplug/README.md

+| Type | Description |
+|------|-------------|
+| NBIRTH | Node Birth Certificate - Edge node announces itself |
+| NDEATH | Node Death Certificate - Edge node goes offline (LWT) |
+| DBIRTH | Device Birth Certificate - Device announces itself |
+| DDEATH | Device Death Certificate - Device goes offline |
+| NDATA | Node Data - Metrics from the edge node |
+| DDATA | Device Data - Metrics from a device |
+| NCMD | Node Command - Command to the edge node |
+| DCMD | Device Command - Command to a specific device |
+| STATE | Host Application state |
+


The markdown tables in this README use || instead of standard table | delimiters (e.g., the “Message Types” table). As written, these won’t render as tables on GitHub. Convert them to proper GitHub-flavored markdown tables (single | with a header separator row).

Copilot · 2026-02-06T15:56:23Z

examples/include.am

 dist_example_DATA+= examples/mqttnet.c \
                    examples/mqttexample.c \
                    examples/mqttport.c \
                    examples/mqttclient/mqttclient.c \
                    examples/mqttsimple/mqttsimple.c \
                    examples/firmware/fwpush.c \
                    examples/firmware/fwclient.c \
                    examples/azure/azureiothub.c \
                    examples/aws/awsiot.c \
                    examples/wiot/wiot.c
 dist_example_DATA+= examples/nbclient/nbclient.c
 dist_example_DATA+= examples/multithread/multithread.c
 if BUILD_SN
 dist_example_DATA+= examples/sn-client/sn-client.c
 dist_example_DATA+= examples/sn-client/sn-client_qos-1.c
 dist_example_DATA+= examples/sn-client/sn-multithread.c
 endif
 dist_example_DATA+= examples/pub-sub/mqtt-pub.c
 dist_example_DATA+= examples/pub-sub/mqtt-sub.c
+dist_example_DATA+= examples/sparkplug/sparkplug.c
 if BUILD_WEBSOCKET


examples/include.am adds the Sparkplug example source to dist_example_DATA, but does not include the new examples/sparkplug/README.md (and possibly sparkplug.h) anywhere for make dist packaging. If the project distributes example docs/headers, add these files to the appropriate dist_*/EXTRA_DIST lists so they’re included in release tarballs.

Copilot · 2026-02-06T15:56:23Z

examples/sparkplug/sparkplug.h

+    /* Initialize outputs */
+    if (group_id) group_id[0] = '\0';
+    if (edge_node_id) edge_node_id[0] = '\0';
+    if (device_id) device_id[0] = '\0';
+
+    /* Parse topic: spBv1.0/group/type/node[/device] */
+    matched = XSSCANF(topic, "%15[^/]/%63[^/]/%15[^/]/%63[^/]/%63s",
+        namespace_buf, group_id, type_buf, edge_node_id, device_id);
+


SparkplugTopic_Parse initializes outputs only when the pointers are non-NULL, but then unconditionally passes group_id, edge_node_id, and device_id to XSSCANF. This will crash if any of those pointers are NULL, despite the signature implying they’re optional. Make the parameters required (and assert/return BAD_ARG when NULL) or scan into local temp buffers and copy out conditionally.

Copilot · 2026-02-06T15:56:23Z

examples/sparkplug/sparkplug.h

+    /* Parse topic: spBv1.0/group/type/node[/device] */
+    matched = XSSCANF(topic, "%15[^/]/%63[^/]/%15[^/]/%63[^/]/%63s",
+        namespace_buf, group_id, type_buf, edge_node_id, device_id);
+
+    if (matched < 4) {
+        return MQTT_CODE_ERROR_BAD_ARG;
+    }
+
+    /* Verify namespace */
+    if (XSTRCMP(namespace_buf, SPARKPLUG_NAMESPACE) != 0) {
+        return MQTT_CODE_ERROR_BAD_ARG;
+    }
+


SparkplugTopic_Parse ignores the *_len parameters and uses hard-coded %63 field widths when scanning into group_id/edge_node_id/device_id. If a caller passes smaller buffers, this can overflow. Use widths derived from the provided lengths (len-1) and/or parse manually using delimiters.

embhorn and others added 3 commits February 5, 2026 15:27

Add Sparkplug example section to main README

fffbff7

Link to examples/sparkplug/README.md for detailed documentation. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

embhorn self-assigned this Feb 5, 2026

embhorn and others added 2 commits February 5, 2026 15:40

Add sparkplug binary to .gitignore

80a2884

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

embhorn requested a review from Copilot February 6, 2026 15:40

Copilot started reviewing on behalf of embhorn February 6, 2026 15:40 View session

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Add Sparkplug B Industrial IoT Example#461

Add Sparkplug B Industrial IoT Example#461
embhorn wants to merge 5 commits intowolfSSL:masterfrom
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embhorn commented Feb 5, 2026

Autotools - single-threaded (Edge Node only)

Autotools - multi-threaded (both clients)

CMake - multi-threaded

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Sparkplug B Example

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