---
title: "writeAsync(_:length:refcon:)"
framework: IOBluetooth
role: symbol
role_heading: Instance Method
path: "iobluetooth/iobluetoothl2capchannel/writeasync(_:length:refcon:)"
---

# writeAsync(_:length:refcon:)

Writes the given data over the target L2CAP channel asynchronously to the remote device.

## Declaration

```swift
func writeAsync(_ data: UnsafeMutableRawPointer!, length: UInt16, refcon: UnsafeMutableRawPointer!) -> IOReturn
```

## Parameters

- `data`: Pointer to the buffer containing the data to send.
- `length`: The length of the given data buffer.
- `refcon`: User supplied value that gets passed to the write callback.

## Return Value

Return Value Returns kIOReturnSuccess if the data was buffered successfully.

## Discussion

Discussion The length of the data may not exceed the L2CAP channel’s ougoing MTU. When the data has been successfully passed to the hardware to be transmitted, the delegate method -l2capChannelWriteComplete:refcon:status: will be called with the refcon passed into this method. NOTE: This method is only available in macOS 10.2.5 (Bluetooth v1.2) or later.