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


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


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


Optional. Invoked when the transport handle becomes closed.


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.



   $transport = $protocol->transport;

Returns the stored transport object


   $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.


The following methods are delegated to the transport object



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.


   $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.


   $protocol->teardown_transport( $transport );

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


Paul Evans <>