---
name: "POE::Component::Pcap"
section: "3pm"
platform: "linux"
package: "libpoe-component-pcap-perl"
version: "0.04-4"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/POE::Component::Pcap"
---

# POE::Component::Pcap(3pm)

POE Interface to Net::Pcap

```
  ## Need an IO::Handle to $kernel->select_read() upon
  $heap->{fdh} = IO::Handle->new_from_fd( $heap->{fd}, "r" )
    or die "Can't create IO::Handle from pcap fd: $!\n";
```

## NAME

POE::Component::Pcap - POE Interface to Net::Pcap

## SYNOPSIS

```
  use POE::Component::Pcap;
  POE::Component::Pcap->spawn(
                              Alias => 'pcap',
                              Device => 'eth0',
                              Filter => 'host fooble or host blort',
                              Dispatch => 'got_packet',
                              Session => $my_session_id,
                             );
  $poe_kernel->post( pcap => open_live =>
                     'eth0', 80, 1, 100 );
  $poe_kernel->post( pcap => set_filter => 'arp or host zooble' );
  $poe_kernel->post( pcap => set_dispatch => 'target_state' );
  $poe_kernel->post( pcap => 'run' );
  $poe_kernel->post( pcap => 'shutdown' );
```

## DESCRIPTION

POE::Component::Pcap provides a wrapper for using the Net::Pcap module from POE programs.  The component creates a separate session which posts events to a specified session and state when packets are available.

### ARGUMENTS

- Alias

  The alias for the Pcap session.  Used to post events such as `"run"` and `"shutdown"` to control the component.  Defaults to `"pcap"` if not specified.

- Device

  As a shortcut, the device for Net::Pcap to watch may be specified when creating the component.  If this argument is used, Net::Pcap::open\_live will be called with a snaplen of 80 octets, a timeout of 100ms, and the interface will be put in promiscuous mode. If these values are not suitable, post an `"open_live"` event instead.

- Filter

  Another shortcut, calls Net::Pcap::compile and Net::Pcap::setfilter to set a packet filter.  This can only be used if the **Device** argument is also given; otherwise a `"set_filter"` event should be posted after an `"open_live"` event (since Net::Pcap must have a `"pcap_t"` descriptor to work with).

- Dispatch

  - Session

  These specify the session and state to which events should be posted when packets are received.

### EVENTS

The following examples assume that the component's alias has been set to the default value of **pcap**.

- open\_live

  ```
    $_[KERNEL]->post( pcap => open_live
                      => 'device', [snaplen], [promsic?], [timeout] );
  ```

  Calls Net::Pcap::open\_live.  The device name must be specified.  The snaplen, promiscuous, and timeout parameters default to 80, 1, and 100 respectively.  This event must be posted (or the **Device** argument must have been passed to **spawn()**) before anything else can be done with the component.

- set\_filter

  ```
    $_[KERNEL]->post( pcap => set_filter
                      => 'host fooble or host blort' )
  ```

  Sets the Net::Pcap capture filter.  See [**tcpdump**(8)](/tcpdump/8.md) for details on the filter language used by [**pcap**(3)](/pcap/3.md).

- set\_dispatch

  ```
    $_[KERNEL]->post( pcap => set_dispatch
                      => 'target_state', 'target_session' );
  ```

  Sets the state and session to which events are sent when packets are received.  The target session will default to the sender of the event if not specified.

  The event posted will have a single argument (available as **ARG0**) which will be an array reference containing the `$hdr` and `$pkt` parameters from Net::Pcap.  See the **Net::Pcap**(3) documentation for more details.

- run

  ```
    $_[KERNEL]->post( pcap => 'run' );
  ```

  Causes the component to register a select\_read and start watching for packets.

- shutdown

  ```
    $_[KERNEL]->post( pcap => 'shutdown' );
  ```

  Shuts the component down.  Causes Net::Pcap::close to be called.

## SEE ALSO

**Net::Pcap**(3), [**pcap**(3)](/pcap/3.md), [**tcpdump**(8)](/tcpdump/8.md), **POE**(3), **POE::Component**(3)

## AUTHOR

Mike Fletcher, \<fletch@phydeaux.org\>

## COPYRIGHT

Copyright 2000-2001, Mike Fletcher.  All Rights Reserved.  This is free software; you may redistribute it and/or modify it under the same terms as Perl itself.