---
title: "system.serial.readBytes"
description: "Read numberOfBytes bytes from a serial port."
---

# system.serial.readBytes

> Read numberOfBytes bytes from a serial port.

This function is used in **Python Scripting**.

## Description
Read `numberOfBytes` bytes from a serial port.

## Client Permission Restrictions
This scripting function has no [Client Permission](../../../ignition-modules/vision/vision-project-properties/vision-project-properties.md#vision-permissions-properties) restrictions.

## Syntax
`system.serial.readBytes(port, numberOfBytes [, timeout])`

### Parameters
Type | Parameter | Description 
------- | ------- | ------
String| `port` | The previously configured serial port to use.
int| `numberOfBytes` | The number of bytes to read.
int| `timeout` | Maximum amount of time, in milliseconds, to block before returning. Default is 5000. [optional]

### Returns
**List[Byte]** - A list containing bytes read from the serial port.
### Scope
Gateway, Vision Client, Perspective Session

## Code Example
```python title="Code Snippet"
# This example will read a specified number of bytes from a port called "COM1".
port = "COM1"
 
system.serial.readBytes("COM1",2)
```