The limits that apply to the MQTT API today, in one place. Where the Enforced by column names a response code, the reader rejects a value past the limit with that code; every code is listed in Response Codes. The field-level definitions are in the MQTT API reference.
Messages and Commands
| Limit | Supported limit | Enforced by |
|---|
| Command queue | 10 commands. Commands beyond that are lost, not delayed | Not reported with a code |
| Command payload size | 16384 bytes | Not specified in the available sources |
dataEVT message size | 6144 bytes. A larger message is dropped without notice | Not reported with a code |
Records per dataEVT | Not specified in the available sources | — |
| Command timeout | Not specified in the available sources | — |
Endpoints and Topics
| Limit | Supported limit | Enforced by |
|---|
| Saved endpoints per reader | 10 | Not specified in the available sources |
endpointName | 15 characters | Not specified in the available sources |
Endpoint url | 511 characters | Not specified in the available sources |
tenantId | 48 characters | Code 27 |
publishTopics entries per endpoint | 3 | Code 25 |
subscribeTopics entries per endpoint | 1 | Code 26 |
mqttParams.keepAlive | 65,535 seconds | Not specified in the available sources |
batching.reportingInterval | 1000 to 60000 ms; 0 selects 1000 | Not specified in the available sources |
batching.maxPayloadSizePerReport | 1024 to 5120 bytes; 0 selects 1024 | Not specified in the available sources |
Reading and Filtering
| Limit | Supported limit | Enforced by |
|---|
Pre-filters (select) | 32 | Code 24 |
tagPattern in a pre-filter | 64 hex characters, an even count | Code 28 |
Access-operation password | Exactly 8 hex characters (32 bits) | Not specified in the available sources |
| Post-filter rules | Not specified in the available sources | — |
Network and Certificates
| Limit | Supported limit | Enforced by |
|---|
| Saved Wi-Fi profiles | Not specified in the available sources | Code 19 when full |
| ESSID | 1 to 32 octets | Not specified in the available sources |
| WPA-Personal pre-shared key | 8 to 63 characters | Not specified in the available sources |
| Certificate content | 4 KB (4096 bytes) per certificate file | Not specified in the available sources |
| Certificates installed at once | 4 | Not specified in the available sources |
| Certificate encoding | PEM, or base64-encoded PEM; private keys in PKCS1 | Code 34 when base64 decoding fails |
Events
| Limit | Supported limit | Enforced by |
|---|
Heartbeat interval | 65,535 seconds | Not specified in the available sources |
Related: 📕 Response Codes · 📕 Endpoints and Topic Slots · 📕 Changing an Endpoint · 📙 Manage Tag Data Throughput · 🔤 Glossary