---
tag: api
type: function
name: publish
params:
- name: topic
  description: the topic to publish to
  type: const char[]
- name: payload
  description: the message to publish
  type: const char[], byte[]
- name: length
  optional: true
  description: the length of the payload. Required if <span class="methodparams">payload</span> is a <span class="methodparamstype">byte[]</span>
  type: unsigned int
- name: retained
  optional: true
  description: whether the message should be retained
      <ul>
          <li>false - not retained</li>
          <li>true - retained</li>
      </ul>
  type: boolean
returns:
  type: boolean
  values:
    - value: 'false'
      description: publish failed, either connection lost or message too large
    - value: 'true'
      description: publish succeeded
---

Publishes a message to the specified topic.