/// <summary>
/// Selects a stream-method from the list of advertised methods.
/// </summary>
/// <param name="feature">The 'feature' element containing the data-form
/// with advertised stream-methods.</param>
/// <returns>The selected stream-method.</returns>
/// <exception cref="ArgumentException">None of the advertised methods is
/// supported.</exception>
private string SelectStreamMethod(XmlElement feature)
{
// See if we support any of the advertised stream-methods.
DataForm form = FeatureNegotiation.Parse(feature);
ListField field = form.Fields["stream-method"] as ListField;
// Order of preference: Socks5, Ibb.
string[] methods = new string[] {
"http://jabber.org/protocol/bytestreams",
"http://jabber.org/protocol/ibb"
};
for (int i = 0; i < methods.Length; i++)
{
if (ForceInBandBytestreams &&
methods[i] != "http://jabber.org/protocol/ibb")
{
continue;
}
if (field.Values.Contains(methods[i]))
{
return(methods[i]);
}
}
throw new ArgumentException("No supported method advertised.");
}
/// <summary>
/// Invoked whenever a 'Stream Initiation' request for file transfers
/// is received.
/// </summary>
/// <param name="from">The JID of the XMPP entity that wishes to initiate
/// the data-stream.</param>
/// <param name="si">The 'si' element of the request.</param>
/// <param name="result">The response to the SI request or an error element to include
/// in the IQ response.</param>
private void OnStreamInitiationRequest(Jid from, XmlElement si, Action <XmlElement> result)
{
try
{
string method = SelectStreamMethod(si["feature"]);
// If the session-id is already in use, we cannot process the request.
string sid = si.GetAttribute("id");
if (String.IsNullOrEmpty(sid) || siSessions.ContainsKey(sid))
{
result(new XmppError(ErrorType.Cancel, ErrorCondition.Conflict).Data);
}
// Extract file information and hand to user.
var file = si["file"];
string desc = file["desc"] != null ? file["desc"].InnerText : null,
name = file.GetAttribute("name");
int size = int.Parse(file.GetAttribute("size"));
FileTransfer transfer = new FileTransfer(from, im.Jid, name, size,
sid, desc);
TransferRequest.Invoke(transfer, (string savePath) =>
{
try
{
// User has rejected the request.
if (savePath == null)
{
result(new XmppError(ErrorType.Cancel, ErrorCondition.NotAcceptable).Data);
}
else
{
// Create an SI session instance.
SISession session = new SISession(sid, File.OpenWrite(savePath),
size, true, from, im.Jid, im.GetExtension(method) as IDataStream);
siSessions.TryAdd(sid, session);
// Store the file's meta data.
metaData.TryAdd(sid, new FileMetaData(name, desc));
// Construct and return the negotiation result.
result(Xml.Element("si", "http://jabber.org/protocol/si").Child(
FeatureNegotiation.Create(new SubmitForm(
new ListField("stream-method", method)))));
}
}
catch (Exception e)
{
System.Diagnostics.Debug.WriteLine("Exception raised", e.ToString() + e.StackTrace);
result(new XmppError(ErrorType.Cancel, ErrorCondition.BadRequest).Data);
}
});
}
catch (Exception e)
{
System.Diagnostics.Debug.WriteLine("Exception raised", e.ToString() + e.StackTrace);
result(new XmppError(ErrorType.Cancel, ErrorCondition.BadRequest).Data);
}
}
/// <summary>
/// Creates the 'feature' XML element which is part of a 'Stream Initiation'
/// request.
/// </summary>
/// <param name="streamOptions">An enumerable collection of accepted stream
/// methods.</param>
/// <returns>An XML 'feature' element.</returns>
/// <exception cref="ArgumentNullException">The streamOptions parameter
/// is null.</exception>
private XmlElement CreateFeatureElement(IEnumerable <string> streamOptions)
{
streamOptions.ThrowIfNull("streamOptions");
// Create the data-form for stream-method selection.
DataForm form = new RequestForm();
HashSet <Option> options = new HashSet <Option>();
foreach (string opt in streamOptions)
{
options.Add(new Option(opt));
}
form.Fields.Add(new ListField("stream-method", true, null, null,
options));
// Wrap it in a 'feature' element to create the offer.
return(FeatureNegotiation.Create(form));
}
/// <summary>
/// Parses the selected stream-method from the specified 'feature' XML
/// element.
/// </summary>
/// <param name="feature">The 'feature' XML element.</param>
/// <returns>The stream method contained in the 'feature' XML
/// element.</returns>
/// <exception cref="ArgumentNullException">The feature parameter is
/// null.</exception>
/// <exception cref="ArgumentException">The feature element contains
/// invalid data.</exception>
private string ParseStreamMethod(XmlElement feature)
{
feature.ThrowIfNull("feature");
DataForm form = FeatureNegotiation.Parse(feature);
// The data-form must contain a field named 'stream-method'.
var field = form.Fields["stream-method"];
if (field == null)
{
throw new ArgumentException("Missing or erroneous 'stream-method' field.");
}
string selected = field.Values.FirstOrDefault();
if (selected == null)
{
throw new ArgumentException("No stream-method selected.");
}
return(selected);
}