UWP, how to read ALL data from StreamSocket

Question

I am trying to implement an XMPP client for UWP in C #, and for this I use StreamSocketfor TCP.

The problem is that for a handshake and SASL authI need a sequence of "write and read" from the client to the server and without delay I can not read all the data sent by the server; I want to remove the delay.

This is my code:

// Start handshake
await XmppWrite("<?xml version='1.0'?><stream:stream to='" + serverHostName.Domain + "' xmlns='jabber:client' xmlns:stream='http://etherx.jabber.org/streams' version='1.0'>");
var responseStream = await XmppRead();

SaslPlain saslPlain = new SaslPlain(Username, Password);
responseStream = null;
String xml = null;
while (!saslPlain.IsCompleted && (xml = saslPlain.GetNextXml(responseStream)) != null)
{
    await XmppWrite(xml);
    responseStream = await XmppRead();
}
if (!saslPlain.IsSuccess) return;

// Request bind
await XmppWrite("<?xml version='1.0'?><stream:stream to='" + serverHostName.Domain + "' xmlns='jabber:client' xmlns:stream='http://etherx.jabber.org/streams' version='1.0'>");
responseStream = await XmppRead();

// Bind
await XmppWrite("<iq id='" + GenerateId() + "' type='set'><bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'/></iq>");
responseStream = await XmppRead();
if (responseStream.Jid == null) return;

Jid = responseStream.Jid;

// Open session
await XmppWrite("<iq id='" + GenerateId() + "' type='set'><session xmlns='urn:ietf:params:xml:ns:xmpp-session'/></iq>");
responseStream = await XmppRead();

The XmppRead () method is as follows:

private async Task<XmppStream> XmppRead()
{
    await Task.Delay(100); // Things don't works without this...
    var x = await dataReader.LoadAsync(BUFFER_SIZE);
    if (dataReader.UnconsumedBufferLength > 0)
    {
        Debug.WriteLine(x + ", " + dataReader.UnconsumedBufferLength);
        var stream = new XmppStream(dataReader.ReadString(dataReader.UnconsumedBufferLength));
        if (stream.IsError)
        {
            if (Error != null)
            {
                Error(this, new XmppClientEventArgs(stream));
            }
            throw new Exception(stream.Error);
        }
        return stream;
    }
    return new XmppStream();
}

So, I think the problem is that I'm trying to read before the server finishes sending all my data, so I can only read a partial message. How can I check if there is other data without a block?

Thanks.