ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Sockets
The following restrictions apply to how and where content in Flash Player or in an AIR application outside of the
application security sandbox can use an XMLSocket object to connect to the server:
For content outside of the application security sandbox, the XMLSocket.connect() method can connect only to
TCP port numbers greater than or equal to 1024. One consequence of this restriction is that the server daemons
that communicate with the XMLSocket object must also be assigned to port numbers greater than or equal to 1024.
Port numbers below 1024 are often used by system services such as FTP (21), Telnet (23), SMTP (25), HTTP (80),
and POP3 (110), so XMLSocket objects are barred from these ports for security reasons. The port number
restriction limits the possibility that these resources will be inappropriately accessed and abused.
For content outside of the application security sandbox, the XMLSocket.connect() method can connect only to
computers in the same domain where the content resides. (This restriction is identical to the security rules for
URLLoader.load().) To connect to a server daemon running in a domain other than the one where the content
resides, you can create a cross-domain policy file on the server that allows access from specific domains. For details
on cross-domain policy files, see “AIR security” on page 1065.
Note: Setting up a server to communicate with the XMLSocket object can be challenging. If your application does not
require real-time interactivity, use the URLLoader class instead of the XMLSocket class.
You can use the XMLSocket.connect() and XMLSocket.send() methods of the XMLSocket class to transfer XML to
and from a server over a socket connection. The XMLSocket.connect() method establishes a socket connection with
a web server port. The XMLSocket.send() method passes an XML object to the server specified in the socket
connection.
When you invoke the XMLSocket.connect() method, the application opens a TCP/IP connection to the server and
keeps that connection open until one of the following occurs:
The XMLSocket.close() method of the XMLSocket class is called.
No more references to the XMLSocket object exist.
Flash Player exits.
The connection is broken (for example, the modem disconnects).
Connecting to a server with the XMLSocket class
Flash Player 9 and later, Adobe AIR 1.0 and later
To create a socket connection, you must create a server-side application to wait for the socket connection request and
send a response to the Flash Player or AIR application. This type of server-side application can be written in AIR or in
another programming language such as Java, Python, or Perl. To use the XMLSocket class, the server computer must
run a daemon that understands the simple protocol used by the XMLSocket class:
XML messages are sent over a full-duplex TCP/IP stream socket connection.
Each XML message is a complete XML document, terminated by a zero (0) byte.
An unlimited number of XML messages can be sent and received over a single XMLSocket connection.
Creating and connecting to a Java XML socket server
Flash Player 9 and later, Adobe AIR 1.0 and later
The following code demonstrates a simple XMLSocket server written in Java that accepts incoming connections and
displays the received messages in the command prompt window. By default, a new server is created on port 8080 of
your local machine, although you can specify a different port number when starting your server from the command
line.
Last updated 6/6/2012
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