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pubsubclient/_posts/2000-10-01-configoptions.md
2020-05-21 01:17:42 +01:00

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---
tag: docs
type: other
title: Configuration Options
---
The following configuration options can be used to configure the library.
They are contained in `PubSubClient.h`.
<dl>
<dt><code>MQTT_MAX_PACKET_SIZE</code></dt>
<dd>Sets the largest packet size, in bytes, the client will handle. Any
packet received that exceeds this size will be ignored.
<p>This value can be overridden by calling <a href="#setBufferSize"><code>setBufferSize(size)</code></a>.</p>
<p>Default: 128 bytes</p>
</dd>
<dt><code>MQTT_KEEPALIVE</code></dt>
<dd>Sets the keepalive interval, in seconds, the client will use. This
is used to maintain the connection when no other packets are being
sent or received.
<p>This value can be overridden by calling <a href="#setKeepAlive"><code>setKeepAlive(keepAlive)</code></a>.</p>
<p>Default: 15 seconds</p>
</dd>
<dt><code>MQTT_VERSION</code></dt>
<dd>Sets the version of the MQTT protocol to use.
<p>Default: MQTT 3.1.1</p>
</dd>
<dt><code>MQTT_MAX_TRANSFER_SIZE</code></dt>
<dd>Sets the maximum number of bytes passed to the network client in each
write call. Some hardware has a limit to how much data can be passed
to them in one go, such as the Arduino Wifi Shield.
<p>Default: undefined (complete packet passed in each write call)</p>
</dd>
<dt><code>MQTT_SOCKET_TIMEOUT</code></dt>
<dd>Sets the timeout when reading from the network. This also applies as
the timeout for calls to <code>connect</code>.
<p>This value can be overridden by calling <a href="#setSocketTimeout"><code>setSocketTimeout(timeout)</code></a>.</p>
<p>Default: 15 seconds</p>
</dd>
</dl>