LwM2M Execute Operation Has No Effect

In this tutorial, you'll learn about LwM2M Execute Operation Has No Effect. We cover key concepts, practical examples, and best practices.

The Problem

LwM2M Execute (E) operation on a resource returns success but nothing happens.

Quick Fix

Wrong

// Execute handler returns success but does nothing
static int exec_handler(anjay_t *anjay, const anjay_dm_object_def_t *obj,
                        anjay_iid_t iid, anjay_rid_t rid,
                        anjay_execute_ctx_t *ctx) {
  return 0;  // No action taken
}```

Server receives 2.04 Changed but device does not reboot/action.

### Right

```cpp
#include <anjay/anjay.h>
#include <anjay/dm.h>

static bool pending_reboot = false;

static int reboot_exec(anjay_t *anjay, const anjay_dm_object_def_t *obj,
                       anjay_iid_t iid, anjay_rid_t rid,
                       anjay_execute_ctx_t *ctx) {
  // Action taken here
  pending_reboot = true;

  // Parse any arguments from the execute
  int buf[16];
  size_t len = anjay_execute_get_args(ctx, buf, sizeof(buf));

  Serial.print("Reboot execute received. Args length: ");
  Serial.println(len);

  return 0;  // Success — server sees 2.04
}

void loop() {
  anjay_sched_run(anjay);

  if (pending_reboot) {
    delay(100);
    ESP.restart();  // Actual action
  }
}```

Server receives 2.04 Changed. Device reboots after 100ms delay.

## Prevention

LwM2M Execute is used for actions (reboot, factory reset, <a href="/embedded-systems/firmware-updates/">firmware update</a>). The resource must have the E (Execute) operation bit set. The handler parses optional arguments from the CoAP payload. Execute always returns 2.04 Changed on success. Actual action may be deferred — the handler should not block for long operations.

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

## FAQ

<details style="margin-bottom:12px;border:1px solid #e2e8f0;border-radius:10px;overflow:hidden"><summary style="cursor:pointer;padding:14px 18px;font-weight:600;font-size:1.05rem;background:#f8fafc;border-bottom:1px solid #e2e8f0;color:#1e293b">### What resources support Execute?</summary><div style="padding:14px 18px;color:#475569;line-height:1.7;background:#fff"><p>Common: Device/Reboot (3/0/4), <a href="/embedded-systems/firmware-updates/">Firmware Update</a>/Update (5/0/0), Device/Factory Reset (3/0/5). Custom resources can also support Execute.</p>
<h3 id="can-execute-pass-arguments">Can Execute pass arguments?</h3><p>Yes. The CoAP POST payload carries arguments. Common: <a href="/embedded-systems/firmware-updates/">firmware update</a> URI, factory reset PIN code.</p>
<h3 id="what-is-asynchronous-execute">What is asynchronous Execute?</h3><p>Execute triggers a long-running action. The client responds 2.04 immediately, performs the action, then sends a notification when complete. Prevents timeout.</p>
</div></details>