# Polling and Reconnection

This page explains how Integrated POS handles validation, reconnection, and resilience when communication is interrupted or the terminal state is uncertain.

## What are polling and reconnection

**Polling** is the command used to verify whether the POS terminal is available and ready to receive commands from the automation system. **Reconnection** refers to the behaviour and flows that apply when communication is lost or when you use setup parameters (e.g. friendly name) during connector creation in SDK-based connections. Robust handling of these scenarios maintains transactional integrity and prevents inconsistent terminal states.

## Executing polling

Call the `Polling` method on the Connector instance before initiating any device operation. A successful response — `Code` `0` with `Connected` `true` — confirms the terminal is available and ready to process operations. Run Polling before each operation to avoid sending commands to an unready terminal.

## Reconnection scenarios

The terminal may reset its connection state — for example after a reboot, a network drop, a USB disconnection, or a temporary cloud/service interruption. When this happens, a device operation (such as `Sale`) returns **code `5`**. Code `5` is the reconnection signal, and it can occur at any time after a drop — not only at startup.

To recover, keep the **same Connector instance** — do not create a new one:

1. Call `Polling` again on the existing Connector.
2. When `Polling` returns code `0`, resend the setup parameters, because reconnection resets the terminal configuration.
3. Resend the command that returned code `5`.

This flow is identical across the SDK (USB / HTTP) and Cloud2Cloud modes.

## Related resources

* [Quick Start](/en/integrated-pos/first-steps-pos/quickstart-integrated-pos) — Step 2 uses Polling to validate the terminal before a sale.
* [Connection Models](/en/integrated-pos/first-steps-pos/connection-models) — Choose USB, network, or cloud; reconnection behaviour varies by model.
* For Polling parameters/return and Reconnection Flow details, see the connectivity and error handling sections of this documentation.