Retrieving a list of network interfaces in Adobe AIR 2
Modified
10 June 2010
Requirements
Prerequisite knowledge
This article is intended for developers who are comfortable with ActionScript and who have a basic understanding of networking.
User Level
All
Required products
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 flash.net.NetworkInfo;
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: 153.32.154.241
Broadcast: 153.32.155.255
PrefixLength: 22
IPVersion: IPv4
Name: en1
DisplayName:
MTU: 1500
HardwareAddr: 00:23:6c:96:ab:c1
Active: true
Addr: 10.4.217.218
Broadcast: 10.4.219.255
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.
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