Starting the File Transfer
The search results are displayed on the MainFileAglet GUI in a Search Results list box. The user can select an element containing the path to the located file from this list box and click the FETCH & OPEN button to call the createFileTransferAglet method on the MainFileAglet with the file path and Remote URL as an argument:

    MainAglet.createFileTransferAglet(
       filePath.replace('\\','/'),remoteUrl.trim());

In the createFileTransferAglet the code actually creates the FileTransferAglet on the local machine. FileTransferAglet is responsible for bringing the sought file from the remote machine to the local machine. As with the FileSearchAglet, the FileTransferAglet is first created on the local machine and the proxy of the MainFileAglet is passed as an argument:

    AgletProxy proxy=context.createAglet(homeUrl,
       "examples.newfilesearch.FileTransferAglet",getProxy());

When the FileTransferAglet is created, its onCreation method is executed. The method receives a reference to the MailFileAglet as its argument. This proxy is used by the FileTransferAglet to send messages to the MainFileAglet.

Below is the code snippet of the onCreation method of FileTransferAglet:

public void onCreation(Object proxy)
{
    //Getting the proxy of the aglet who created this aglet.
    MainAgletProxy=(AgletProxy)proxy;
    //....

We also create an itinerary for the FileTransferAglet that dispatches this aglet from one machine to another:

     //Creating an itinerary object to control
     //the travel path of this aglet.
     itinerary = new SimpleItinerary(this);

The code then compiles data for the file transfer by instantiating the FileTransferData class. The file transfer data contains the remote file path and the Remote URL that contains the file sought:

//Creating an object of the "FileTransferData" class.
     FileTransferData fileTransferObj=
     new FileTransferData(filePath,remoteUrl);

It then sends a message called Go to the created FileTransferAglet with the FileTransferData object as an argument:

//Sending message "Go" to the "File Transfer Agent" //with an argument with it.
    proxy.sendOnewayMessage(new Message("Go",(Object)fileTransferObj));

The Go message is processed by the handleMessage method of the FileTransferAglet. The message handler retrieves the file transfer data from the message and then calls the startTrip method:

public boolean handleMessage(Message msg)
{
//.....
    else if(msg.sameKind("Go"))
    {
    //Getting the argument send with this message.
       fileTransObj=(FileTransferData)msg.getArg();
       remoteUrl=fileTransObj.remoteUrl;
       filePath=fileTransObj.filePath;
startTrip();
    }
//....
}

The startTrip method dispatches the aglet to the appropriate machine:

private void startTrip()
{
//.....
//Dispatch this aglet to remote machine as specified
//in file search criteria and sends message "atRemote"
//to itself when it reaches the remote machine.
    itinerary.go(""+remoteUrl, "atRemote");
    //.....
}

Once the FileTransferAglet reaches the remote machine, it sends itself the atRemote message. The message handler for this aglet calls the atRemote method. The code inside the atRemote method creates an inputstream to read from the required file and then reads the bytes into a byte buffer. Once it's read the bytes from the file it dispatches itself back to the home location, i.e., the user machine:

private void atRemote()
{
//....
//Creating byte array to hold the contents of the file.
    fileTransObj.bytes = new byte[(int)len];
    int offset = 0;
    int numRead = 0;
    //Putting the contents of the file into the bytes array.
    while(offset< fileTransObj.bytes.length
    && (numRead=is.read(fileTransObj.bytes, offset,
    fileTransObj.bytes.length - offset )) >= 0)
    {
    offset += numRead;
    }
    // Dispatch this agent to user machine.
    itinerary.go(homeUrl, "atHome");
    //....
}