Developer Guide
Writing data to a socket
To write data to a socket connection, you call any of the write methods in the Socket class (such as writeBoolean(),
writeByte(), writeBytes(), or writeDouble()), and then flush the data in the output buffer using the flush()
method. In the Telnet server, data is written to the socket connection using the
writeBytes() method which takes
the byte array as a parameter and sends it to the output buffer. The
writeBytesToSocket() method is as follows:
public function writeBytesToSocket(ba:ByteArray):void
This method gets called by the sendCommand() method of the main application file.
Displaying messages from the socket server
Whenever a message is received from the socket server, or an event occurs, the custom msg() method is called. This
method appends a string to the TextArea on the Stage and calls a custom
setScroll() method, which causes the
TextArea component to scroll to the very bottom. The
msg() method is as follows:
private function msg(value:String):void
ta.text += value;
If you didnt automatically scroll the contents of the TextArea component, users would need to manually drag the
scroll bars on the text area to see the latest response from the server.
Scrolling a TextArea component
The setScroll() method contains a single line of ActionScript that scrolls the TextArea component’s contents
vertically so the user can see the last line of the returned text. The following snippet shows the
setScroll() method:
public function setScroll():void
ta.verticalScrollPosition = ta.maxVerticalScrollPosition;
This method sets the verticalScrollPosition property, which is the line number of the top row of characters
that is currently displayed, and sets it to the value of the
maxVerticalScrollPosition property.
Example: Uploading and downloading files
The FileIO example demonstrates techniques for performing file downloading and uploading in Flash Player. These
techniques are:
Downloading files to a user’s computer
Uploading files from a user’s computer to a server
Cancelling a download in progress
Cancelling an upload in progress
Developer Guide
To get the application files for this sample, see The
FileIO application files are found in the Samples/FileIO folder. The application consists of the following files:
FileIO application overview
The FileIO application contains the user interface that allows a user to upload or download files using Flash Player.
The application first defines a couple of custom components, FileUpload and FileDownload, which can be found in
the com.example.programmingas3.fileio package. Once each custom component dispatches its
event, the component’s
init() method is called and passes references to a ProgressBar and Button component
instance, which allow users to see the files upload or download progress or cancel the file transfer in progress.
The relevant code from the FileIO.mxml file is as follows (Note that in the Flash version, the FLA file contains
components placed on the stage, whose names match the names of the Flex components described in this step):
<example:FileUpload id="fileUpload" creationComplete="fileUpload.init(uploadProgress,
cancelUpload);" />
<example:FileDownload id="fileDownload"
creationComplete="fileDownload.init(downloadProgress, cancelDownload);" />
The following code shows the Upload File panel, which contains a progress bar and two buttons. The first button,
startUpload, calls the FileUpload.startUpload() method, which calls the FileReference.browse()
method. The following excerpt shows the code for the Upload File panel:
<mx:Panel title="Upload File" paddingTop="10" paddingBottom="10" paddingLeft="10"
<mx:ProgressBar id="uploadProgress" label="" mode="manual" />
<mx:ControlBar horizontalAlign="right">
<mx:Button id="startUpload" label="Upload..." click="fileUpload.startUpload();" />
<mx:Button id="cancelUpload" label="Cancel" click="fileUpload.cancelUpload();"
enabled="false" />
This code places a ProgressBar component instance and two Button component button instances on the Stage. When
the user clicks the Upload button (
startUpload), an operating system dialog box is launched that allows the user
to select a file to upload to a remote server. The other button,
cancelUpload, is disabled by default, although when
a user begins a file upload, the button becomes enabled and allows the user to abort the file transfer at any time.
The code for the Download File panel is as follows:
<mx:Panel title="Download File" paddingTop="10" paddingBottom="10" paddingLeft="10"
<mx:ProgressBar id="downloadProgress" label="" mode="manual" />
<mx:ControlBar horizontalAlign="right">
<mx:Button id="startDownload" label="Download..."
click="fileDownload.startDownload();" />
File Description
The main application file in Flash (FLA) or Flex (MXML).
com/example/programmingas3/fileio/ A class that includes methods for downloading files from a server.
com/example/programmingas3/fileio/ A class that includes methods for uploading files to a server.

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