Broker websocket by embhorn · Pull Request #466 · wolfSSL/wolfMQTT

embhorn · 2026-02-12T22:42:27Z

Add websocket support to broker.
Also cleanup client lib websocket logic.
Also update agents.md
Added broker with websockets tests

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Pull request overview

Adds WebSocket (libwebsockets) support to the embedded broker, aligns the WebSocket client example with the libwebsockets TLS model, and updates docs/tests/CI to exercise the new transport.

Changes:

Add a libwebsockets-backed WebSocket listener to the broker and route broker-side MqttNet I/O through WebSocket callbacks.
Adjust TLS socket helper compilation guards and update the WebSocket client example to avoid wolfSSL socket-TLS setup (TLS handled by libwebsockets).
Extend broker tests and CI to build/run with WebSocket enabled; update AGENTS.md.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
wolfmqtt/mqtt_socket.h	Broaden TLS helper function visibility when WebSocket is enabled.
wolfmqtt/mqtt_broker.h	Add broker and per-client fields for WebSocket support.
src/mqtt_socket.c	Match TLS helper compilation guards with header changes.
src/mqtt_broker.c	Implement broker-side libwebsockets server + integration into broker loop/CLI.
src/include.am	Link broker binary with `-lwebsockets` when WebSocket is built.
scripts/broker.test	Add an end-to-end WebSocket connect/subscribe test.
examples/websocket/websocket_client.c	Prevent socket-TLS setup for WebSocket connections (TLS handled by LWS).
examples/websocket/net_libwebsockets.c	Add compatibility macro for protocol list terminator.
AGENTS.md	Document broker feature and testing/build options.
.github/workflows/broker-check.yml	Add CI matrix entries for broker builds with WebSocket (and WebSocket+TLS).

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src/mqtt_broker.c

scripts/broker.test

src/mqtt_broker.c

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 6 comments.

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src/mqtt_broker.c

scripts/broker.test

src/mqtt_broker.c

Add server-side WebSocket support via libwebsockets, allowing MQTT-over-WebSocket clients to connect alongside regular TCP clients. The broker listens on two ports simultaneously (TCP and WebSocket) with per-client rx/tx buffers bridging the lws push-based callback model to the broker's pull-based polling model. - Add BrokerWsCtx per-client context and WebSocket fields to MqttBroker - Add lws server callback, WS-specific MqttNet read/write/disconnect - Add BrokerClient_AddWs for WebSocket client initialization - Add -w <port> CLI option to enable WebSocket listening - Add local TLS IO callbacks when both WebSocket and TLS are enabled - Fix wolfSSL/OpenSSL header conflict in net_libwebsockets.c client - Link libwebsockets for broker when BUILD_WEBSOCKET is enabled - Add WebSocket test case to broker.test Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add two new matrix entries to broker-check.yml for testing the broker with WebSocket support: plain WebSocket and WebSocket + TLS. Installs libwebsockets-dev and configures wolfSSL with --enable-opensslcoexist for system lws compatibility. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dgarske

awesome! very close

dgarske · 2026-02-17T22:45:32Z

src/mqtt_broker.c

+    else
+#endif
+    {
+        (void)BrokerNetDisconnect(bc);


Consider removing this call, as its done already below at line 950. Or visa versa

dgarske · 2026-02-17T22:46:31Z

src/mqtt_broker.c

+        if (bc_ptr != NULL) {
+            *bc_ptr = NULL;
+        }
+        lws_close_reason(ws->wsi, LWS_CLOSE_STATUS_NORMAL, NULL, 0);


lws_close_reason() sets a close code for use when you return -1 from inside a callback. Called from BrokerWsNetDisconnect (outside any callback), it has no effect — the WebSocket close handshake frame is never sent. The remote peer won't receive a proper close frame. A lws_callback_on_writable + return -1 pattern is needed, or lws_wsi_close() (available in newer lws).

dgarske · 2026-02-17T22:47:03Z

src/mqtt_broker.c

+    /* Request writable callback and service until data is flushed */
+    lws_callback_on_writable((struct lws*)ws->wsi);
+    while (ws->tx_pending != NULL && ws->status > 0 && attempts < 100) {
+        lws_service(lws_get_context((struct lws*)ws->wsi), 0);


This works in practice (single-threaded, and the test passes), but it's architecturally wrong for lws — lws_service re-enters the event loop, processing callbacks for all connections while waiting for one write. If the write doesn't flush in 100 iterations it returns a network error. It happens to work now because the test scenario is simple, but under load or on a slow link this could spin or fail.

dgarske · 2026-02-17T22:47:23Z

src/mqtt_broker.c

+        if (ws->tx_pending != NULL && ws->tx_len > 0) {
+            int n = lws_write(wsi, ws->tx_pending + LWS_PRE,
+                ws->tx_len, LWS_WRITE_BINARY);
+            if (n < (int)ws->tx_len) {


Per lws 4.x docs, lws_write returns -1 on failure or the number of bytes written on success. For binary frames it's expected to write all bytes or return -1. The n < tx_len check would also catch n == 0, treating it as a failure (correct). This is actually fine but a comment explaining the lws guarantee would help.

dgarske · 2026-02-17T22:48:19Z

src/mqtt_broker.c

 #endif
 }

-#ifdef WOLFMQTT_BROKER_WILL


This guard is still needed.

dgarske · 2026-02-17T22:50:09Z

wolfmqtt/mqtt_broker.h

 #endif
 #endif
+#ifdef ENABLE_MQTT_WEBSOCKET
+    void   *ws_ctx;             /* struct lws_context* (opaque) */


Consider a different name here confusing

ws_ctx field name used in both MqttBroker (for lws_context*) and BrokerClient (for BrokerWsCtx*)

embhorn self-assigned this Feb 12, 2026

embhorn force-pushed the broker_websocket branch from 74451e5 to e28a5b0 Compare February 17, 2026 18:47

embhorn marked this pull request as ready for review February 17, 2026 20:19

embhorn requested a review from Copilot February 17, 2026 20:19

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embhorn and others added 2 commits February 17, 2026 15:08

embhorn force-pushed the broker_websocket branch from b1f502d to dba0ca8 Compare February 17, 2026 21:09

embhorn requested a review from dgarske February 17, 2026 22:06

embhorn assigned wolfSSL-Bot and unassigned embhorn Feb 17, 2026

dgarske requested changes Feb 17, 2026

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embhorn commented Feb 12, 2026 •

edited

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