> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hologram.io/llms.txt
> Use this file to discover all available pages before exploring further.

# What is Hologram cloud messaging?

> Hologram cloud messaging forwards data between your device and the internet using the device's cellular data connection. It supports both outbound (device to cloud) and inbound (cloud to device) messaging.

## Outbound (from device)

Messages take the form of a binary payload (usually UTF8-encoded text), and an optional list of event tags that you can use for filtering events or for triggering alerts and sending notifications.

By configuring an alert, you can forward messages to other internet services using webhooks. This lets you automatically forward your messages without deploying code updates to your cellular devices.

<Card title="Event monitoring and alerts" href="/guides/cloud-and-tools/event-types-and-tags" horizontal>
  Learn about how event monitoring works and how to send notifications when events occur
</Card>

<Card title="Event types and tags" href="/guides/cloud-and-tools/event-types-and-tags" horizontal>
  Learn about available event types and tags
</Card>

## Inbound (to device)

Hologram has API endpoints and interface in your dashboard to send **TCP or UDP messages** to any port on your cellular device. This requires that your device run embedded Linux or otherwise implements a networking stack.

We then translate the API requests — or messages sent using your dashboard — into raw TCP/UDP messages and send them to the desired SIM.

<Card title="Dashboard" href="/dashboard/sim-actions/send-messages-to-sims" horizontal>
  Send TCP or UDP messages to any port on your device from your dashboard
</Card>

<Card title="REST API" href="/api/1/devices/messages/post" horizontal>
  Send TCP or UDP messages to any port on your device using the REST API
</Card>