<p>The list of messages to be sent. Each message has the format: { "messageId": "string", "payload": "string"}.</p> <p>The field names of message payloads (data) that you send to IoT Analytics:</p> <ul> <li> <p>Must contain only alphanumeric characters and undescores (_). No other special characters are allowed.</p> </li> <li> <p>Must begin with an alphabetic character or single underscore (_).</p> </li> <li> <p>Cannot contain hyphens (-).</p> </li> <li> <p>In regular expression terms: "^[A-Za-z_]([A-Za-z0-9]*|[A-Za-z0-9][A-Za-z0-9_]*)$". </p> </li> <li> <p>Cannot be more than 255 characters.</p> </li> <li> <p>Are case insensitive. (Fields named foo and FOO in the same payload are considered duplicates.)</p> </li> </ul> <p>For example, {"temp_01": 29} or {"_temp_01": 29} are valid, but {"temp-01": 29}, {"01_temp": 29} or {"__temp_01": 29} are invalid in message payloads. </p>