The following walkthrough demonstrates the steps required to setup file-transfers; It demonstrates how to send as well as how to receive files using the built-in file-transfer methods of XMPP.

Transferring files

  1. In order to proccess incoming file-requests you must provide a delegate of type FileTransferRequest to the XmppClient instance. This delegate is invoked whenever another XMPP user attempts to initiate a file-transfer. It is then this method's responsibility to examine or present the provided meta-data (file name, file size and description) to the user in order to determine whether to accept or refuse the pending file-transfer request. The following example illustrates how to setup the FileTransferRequest delegate.

    CopyC#
    using S22.Xmpp.Client;
using S22.Xmpp.Extensions;
using System;
using System.Threading;

namespace ConsoleApplication54 {
    class Program {
        static void Main(string[] args) {
            string hostname = "jabber.se";
            string username = "myUsername";
            string password = "myPassword";

            using (XmppClient client = new XmppClient(hostname, username, password)) {
                // Setup any event handlers here.
                // ...
                // Provide a FileTransferRequest delegate to the XmppClient instance.
                client.FileTransferRequest = OnFileTransferRequest;
                client.Connect();

                Console.WriteLine("Connected as " + client.Jid);
                Console.WriteLine("Waiting for incoming file-requests...");
                // Block indefinitely.
                Thread.Sleep(Timeout.Infinite);
            }
        }

        /// <summary>
        /// A callback method invoked whenever another user wishes to send us a file.
        /// </summary>
        /// <param name="transfer">
        /// A FileTransfer object containing meta-data about the
        /// respective file.
        /// </param>
        /// <returns>
        /// The location at which to save the incoming file, or null to refuse
        /// the file-request.
        /// </returns>
        static string OnFileTransferRequest(FileTransfer transfer) {
            // Let the user decide whether we want to accept the file-request or not.
            Console.WriteLine("Incoming file-transfer request from <" + transfer.From + ">: ");
            Console.WriteLine(" - Filename: " + transfer.Name);
            Console.WriteLine(" - Filesize: " + transfer.Size + " bytes");
            if (!String.IsNullOrEmpty(transfer.Description))
                Console.WriteLine(" - Description: " + transfer.Description);

            Console.Write("Type Y to accept or N to refuse the request: ");
            string s = Console.ReadLine().ToLowerInvariant();
            if (s == "y")
                // This saves the file in the current working directory of the process.
                return transfer.Name;
            else
                // Returning null indicates we don't wish to accept the file-transfer.
                return null;
        }
    }
}

    Upon accepting a pending request for a file, the progress of the file-transfer operation can be observed by subscribing to the FileTransferProgress event, which is raised periodically as the file is being transferred. If a file-transfer is aborted prematurely, the FileTransferAborted event is raised.

  2. In order to offer a file to another XMPP user, call the InitiateFileTransfer method; The method expects the JID of the recipient, the file you wish to transfer and optionally a callback method that is invoked once the other site has either accepted or rejected the file-transfer request. The following example demonstrates how to initiate a file-transfer with another XMPP user and print the progress of the subsequent file-transfer operation to the console.

    CopyC#
    using S22.Xmpp.Client;
using S22.Xmpp.Extensions;
using System;

namespace ConsoleApplication1 {
    class Program {
        static void Main(string[] args) {
            string hostname = "jabber.se";
            string username = "myUsername";
            string password = "myPassword";
            string recipient = "king_olaf@jabber.no/laptop";

            using (XmppClient client = new XmppClient(hostname, username, password)) {
                // Setup event handlers.
                client.FileTransferProgress += OnFileTransferProgress;
                client.FileTransferAborted += OnFileTransferAborted;

                client.Connect();
                Console.WriteLine("Connected as " + client.Jid);

                while (true) {
                    Console.Write("Type 'send' to initiate the file-transfer, or 'quit' to exit: ");
                    string s = Console.ReadLine().ToLowerInvariant();
                    if (s == "quit")
                        return;
                    if (s == "send") {
                        client.InitiateFileTransfer(recipient, "polarbear_greenland.jpg",
                            "This is a picture of a polar bear from Greenland!", FileTransferCallback);
                    }
                }
            }
        }

        /// <summary>
        /// The callback method invoked once the pending file-transfer has been accepted or
        /// rejected.
        /// </summary>
        /// <param name="accepted">
        /// true if the other site accepted our file-transfer request; Otherwise false.
        /// </param>
        /// <param name="transfer">
        /// A FileTransfer object containing meta-data about the file-transfer.
        /// </param>
        static void FileTransferCallback(bool accepted, FileTransfer transfer) {
            Console.WriteLine(transfer.To + " has " + (accepted == true ? "accepted " : "rejected ") +
                "the transfer of " + transfer.Name + ".");
        }

        static void OnFileTransferProgress(object sender, FileTransferProgressEventArgs e) {
            // Print out the progress of the file-transfer operation.
            Console.WriteLine("Transferring " + e.Transfer.Name + "..." +
                e.Transfer.Transferred + "/" + e.Transfer.Size + " Bytes");
        }

        static void OnFileTransferAborted(object sender, FileTransferAbortedEventArgs e) {
            Console.WriteLine("The transfer of " + e.Transfer.Name + " has been aborted.");
        }
    }
}

See Also