by William Liang

William Liang
William Liang


10 June 2010

Prerequisite knowledge

This article is intended for developers who
are comfortable with ActionScript and who
have a basic understanding of networking.
Required products

User level

Among the new networking features introduced in Adobe AIR 2 is the ability to enumerate all hardware and software network interfaces. This list of network interfaces includes information about each interface such as IP address, MAC address, status, and more.
This article describes the new NetworkInfo class and the information it provides; you can use this information to implement peer-to-peer features and advanced networking applications.

NetworkInfo use cases and class overview

Enumerating all hardware and software network interfaces reveals detailed information about the networking capabilities of the local machine. This information is required for many advanced networking features. For example, peer-to-peer and Voice-over-IP (VoIP) applications frequently need to be able to traverse Network Address Translation (NAT) gateways. In order to traverse a NAT, an application typically needs the list of available network interfaces. The application can then probe each interface to determine if it can be used to traverse the NAT and establish a connection with a remote client.
Peer-to-peer applications often also need to obtain a list of available interfaces and their capabilities. For example, when a Session Initiation Protocol (SIP) client wants to establish a connection with another SIP client, the two clients need to exchange their capabilities. These capabilities include the networking capabilities of the local machine and the networking between them.
In AIR 2, you can now incorporate network information within your application, so you can implement standard networking or peer-to-peer features, such as the ones listed above, or develop new ones.
NetworkInfo class overview
The new NetworkInfo class is analogous to ipconfig on Windows and ifconfig on Mac OS X or Linux. NetworkInfo returns a list of network interfaces and the following information for each interface:
  • Name
  • Display name
  • MTU
  • Hardware address (or MAC address)
  • Active (or status)
  • Address (or IP address)
  • Broadcast address
  • Prefix length
  • IP version (or IP Family)
Using the NetworkInfo class
NetworkInfo is a singleton class. The code below is a simple example of how to use it to display information about the local machine's network interfaces.
import; public function findInterface():void { var results:Vector.<NetworkInterface> = NetworkInfo.networkInfo.findInterfaces(); for (var i:int=0; i<results.length; i++) { var output = output + "Name: " + results[i].name + "\n" + "DisplayName: " + results[i].displayName + "\n" + "MTU: " + results[i].mtu + "\n" + "HardwareAddr: " + results[i].hardwareAddress + "\n" + "Active: " + results[i].active + "\n"; for (var j:int=0; j<results[i].addresses.length; j++) { output = output + "Addr: " + results[i].addresses[j].address + "\n" + "Broadcast: " + results[i].addresses[j].broadcast + "\n" + "PrefixLength: " + results[i].addresses[j].prefixLength + "\n" + "IPVersion: " + results[i].addresses[j].ipVersion + "\n"; } output = output + "\n"; } }
If you run this example on an Apple MacBook Pro, you will get a list of interfaces that minimally contains en0 and en1; for example:
Name: en0 DisplayName: MTU: 1500 HardwareAddr: 00:25:00:a5:35:1e Active: true Addr: 2001:1890:110b:1498:225:ff:fea5:351e Broadcast: PrefixLength: 64 IPVersion: IPv6 Addr: Broadcast: PrefixLength: 22 IPVersion: IPv4 Name: en1 DisplayName: MTU: 1500 HardwareAddr: 00:23:6c:96:ab:c1 Active: true Addr: Broadcast: PrefixLength: 22 IPVersion: IPv4

The network change event

Another useful feature of the NetworkInfo class is the ability to detect network changes. A network change event occurs when a network interface becomes enabled or disabled.
For example, an application may use the NetworkInfo class to obtain a list of currently available network interfaces and select the best candidate interface from that list. Later, if another interface becomes enabled, the application will be notified via a network change event. It can then use that opportunity to determine if the recently enabled interface is a better candidate and reestablish the network connection using the new interface.
Similarly, if an interface becomes disabled or disconnected from the network, the application will receive a network change event, enabling it to take the appropriate action. For example, it may terminate the connection or select another interface and reestablish the connection.
The network change event is fired from the NativeApplication class and bubbled up by the NetworkInfo class. To receive network change events, an application must add an event listener:
NetworkInfo.networkInfo.addEventListener(Event.NETWORK_CHANGE, onNetworkChange);
Alternatively, you can add the event listener on your NativeApplication object:
NativeApplication.nativeApplication.addEventListener(Event.NETWORK_CHANGE, onNetworkChange);

Where to go from here

For further information about the NetworkInfo class and its usage, please refer to the AIR 2 release notes.