---
name: "IO::Async::Protocol"
section: "3pm"
platform: "linux"
package: "libio-async-perl"
version: "0.804-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/IO::Async::Protocol"
---

# IO::Async::Protocol(3pm)

base class for transport-based protocols

## NAME

"IO::Async::Protocol" - base class for transport-based protocols

## DESCRIPTION

This subclass of IO::Async:Notifier provides storage for a  IO::Async::Handle object, to act as a transport for some protocol. It contains an instance of the transport object, which it adds as a child notifier, allowing a level of independence from the actual transport being used. For example, a stream may actually be an IO::Async::SSLStream to allow the protocol to be used over SSL.

This class is not intended to be used directly, instead, see one of the subclasses

- IO::Async::Protocol::Stream - base class for stream-based protocols

  ## EVENTS

The following events are invoked, either using subclass methods or CODE references in parameters:

### on\_closed

Optional. Invoked when the transport handle becomes closed.

## PARAMETERS

The following named parameters may be passed to `"new"` or `"configure"`:

### transport =\> IO::Async::Handle

The IO::Async::Handle to delegate communications to.

### on\_closed =\> CODE

CODE reference for the `"on_closed"` event.

When a new `"transport"` object is given, it will be configured by calling the `"setup_transport"` method, then added as a child notifier. If a different transport object was already configured, this will first be removed and deconfigured using the `"teardown_transport"`.

## METHODS

### transport

```
   $transport = $protocol->transport;
```

Returns the stored transport object

### connect

```
   $protocol->connect( %args );
```

Sets up a connection to a peer, and configures the underlying `"transport"` for the Protocol.

Takes the following named arguments:

- socktype =\> STRING or INT

  Required. Identifies the socket type, and the type of continuation that will be used. If this value is `"stream"` or `"SOCK_STREAM"` then `"on_stream"` continuation will be used; otherwise `"on_socket"` will be used.

- on\_connected =\> CODE

  Optional. If supplied, will be invoked once the connection has been established.

  ```
     $on_connected->( $protocol );
  ```

- transport =\> IO::Async::Handle

  Optional. If this is provided, it will immediately be configured as the transport (by calling `"configure"`), and the `"on_connected"` callback will be invoked. This is provided as a convenient shortcut.

Other arguments will be passed to the underlying IO::Async::Loop `"connect"` call.

## TRANSPORT DELEGATION

The following methods are delegated to the transport object

```
   close
```

## SUBCLASS METHODS

`"IO::Async::Protocol"` is a base class provided so that specific subclasses of it provide more specific behaviour. The base class provides a number of methods that subclasses may wish to override.

If a subclass implements any of these, be sure to invoke the superclass method at some point within the code.

### setup\_transport

```
   $protocol->setup_transport( $transport );
```

Called by `"configure"` when a new `"transport"` object is given, this method should perform whatever setup is required to wire the new transport object into the protocol object; typically by setting up event handlers.

### teardown\_transport

```
   $protocol->teardown_transport( $transport );
```

The reverse of `"setup_transport"`; called by `"configure"` when a previously set-up transport object is about to be replaced.

## AUTHOR

Paul Evans \<leonerd@leonerd.org.uk\>