Tom Krcha's FlashRealtime

Hey amigo!
I am Tom Krcha, Gaming Evangelist at Adobe. These are my notes

Build An App In A Week - Recordings
P2P and LCCS

June 15th, 2010

Last week, my colleagues at Adobe and I organized an online event called Build An App In A Week.

Watch The Recordings

The event was packed with resources for both RIA designers and developers and the goal was to build a complete full-featured app with various functionalities and challenges in just a week.

You can watch all the recordings here.

I was doing two of them - basically about developing multiuser apps, but the main goal was a chat feature inside the app.
One used pure P2P and Cirrus, the other one used LiveCycle Collaboration Service. It’s not just a simple chat application; I also explain how you can build an Instant Messenger, User Lists, Private Messaging, and so on.

P2P Session
Build An App In A Week - Peer-to-Peer

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Directed Routing Explained in Flash 10.1 P2P

June 4th, 2010

Directed Routing enables you to send data to a specific client in the peer-to-peer group (NetGroup). It requires stable and correct topology to work well - still it’s very useful.

There has been already something written about directed routing. But I’d like to share with you much more.

First, let me explain you which methods does what. You have basically three main functions sendToNearest, sendToNeighbor and sendToAllNeighbors. See image below.

P2P Directed Routing Flash 10.1 Peer-to-peer - Click for bigger image
Image: Peer-to-Peer Directed Routing in Flash Player 10.1 [Bigger image]

Continue reading to understand how it all works.
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P2P GroupSpecifier Class Explained In Details Part 1

March 11th, 2010

If you’ve tried my tutorial on creating a simple chat using P2P NetGroup in Flash Player 10.1, you might have been wondering what the other parameters you can set up mean.

GroupSpecifier is a very powerful class and ASDocs are good resource to look in, but I thought I’d write few more words on this topic since it’s easier to understand with a little more explanation.

postingEnabled and multicastEnabled
These are self-explanatory. Just a little note: the difference between Multicast and Posting is simply in the overhead used during their management. Posting should be used when you have lots of senders sending relatively little data (like Chat). Multicast when you have fewer senders sending lots of data (Video, Chat).

Why should I disable P2P when I am building a P2P application? Obvious question. This one is for IP Multicast.
Application-Level-Multicast (so called P2P Multicast) is multicast established over peers.
Native IP Multicast is multicast enabled in the network - it must be supported by routers and the network itself.
Fusion is Application-Level-Multicast and Native IP Multicast used together.
So, when you disable P2P by saying peerToPeerDisabled=true, your app will use only Native IP Multicast, which is more efficient, but works mostly only in closed networks (like a company network).

Opens supporting functions from the server. In the basic scenario it enables auto-bootstrapping. Bootstrapping in this context means adding peers to the group. You can do this manually by calling the addBootstrapPeer function or setting serverChannelEnabled=true to make it automatic. In the P2P Chat example it basically takes care of adding peers to a group and establishes communication between them.

groupspecWithAuthorizations and groupspecWithoutAuthorizations
Difference? Security. If you set a posting or multicast password, the one “with” can post or multicast, the one “without” is receive-only.

Remember - GroupSpecifier is technically a String combined of properties and the name. If you change a property you will be in a different group.

More to come soon.

E-seminar materials: P2P Programming in Flash

March 4th, 2010

As promised, here are the links, presentation and materials I used and covered in my E-seminar on P2P Programming in Flash on Wednesday 3rd March:



Simple chat with P2P NetGroup in FP 10.1

February 9th, 2010

Watch videotutorial of creating P2P Chat with NetGroup in FP 10.1

afcs_logoThis tutorial explains total basics of using P2P/RTMFP Groups in Flash Player 10.1. We are going to build simple multi-user chat using RTMFP Posting - all data will be transferred over P2P! For this purpose we use recently updated (22 Jan 2010) Adobe Cirrus - rendezvous service.

Updated: 4:37 PM Feb 9 2010

Final demo: Try (run in few browsers) | Download source

- Flash Player 10.1
- UDP enabled network (you can’t be behind firewall, which blocks UDP)
- Flash Builder 4
- Cirrus developer key - Get one here if don’t have already. You have to login using your Adobe credentials to get it.
- playerglobal.swc for Flash Player 10.1

Step 1: Create new Flex 4 project
File -> New -> Flex Project
Link new playerglobal.swc (FP10.1 API) to your project in Project Properties and set compiler version in Flex Compiler to 10.1.0


Step 2: Connect to Cirrus
First of all we need to setup NetConnection to Adobe Cirrus. That’s easy part.

private const SERVER:String = "rtmfp://";
private const DEVKEY:String = "YOUR-DEVELOPER-KEY";
private var nc:NetConnection;
private function connect():void{
	nc = new NetConnection();

Step 3: Setup NetGroup
We need to setup P2P group and connect to it. GroupSpecifier is a class, which let’s you to define all the parameters of the group. First you give it a name - in this case “myGroup/g1″. Then you set it to use serverChannel, to let it communicate with Cirrus. Finally we enable Posting. That’s all you have to do to define the P2P Group.
Then we have to define the actual NetGroup. groupspecWithAuthorizations() returns String - it’s a group identifier. Now you probably ask, what’s the difference between groupspecWithoutAuthorizations() and groupspecWithAuthorizations(). If you set a posting or multicast password, the one “with” can post or multicast, the one “without” is receive-only.

private function setupGroup():void{
	var groupspec:GroupSpecifier = new GroupSpecifier("myGroup/g1");
	groupspec.serverChannelEnabled = true;
	groupspec.postingEnabled = true;
	netGroup = new NetGroup(nc,groupspec.groupspecWithAuthorizations());
	user = "user"+Math.round(Math.random()*10000);

Step 4: Handle NetStatusEvent
We are going to handle at this step just three events. When we connect to Cirrus we setup a group. When we connect to NetGroup we reflect it to UI and and when we receive a Posting message we show it in chat history.

private function netStatus(event:NetStatusEvent):void{
		case "NetConnection.Connect.Success":
		case "NetGroup.Connect.Success":
			connected = true;
		case "NetGroup.Posting.Notify":

Step 5: Sending and receiving message
We have to put together a message object, which handles text, user name, sender ID. Sender ID is useful to have for direct posting. And we also convert NetConnection PeerID to GroupAddress - participant address in the group. When we post() message to a NetGroup, we just distribute it/broadcast it, but it does not come back to us. So that’s why we need to call receiveMessage as well - to display it in history text field.

private var seq:int = 0;
private function sendMessage():void{
	var message:Object = new Object();
	message.sender = netGroup.convertPeerIDToGroupAddress(nc.nearID);
	message.user = txtUser.text;
	message.text = txtMessage.text;
	message.sequence = seq++; // *to keep unique;
	txtMessage.text = "";
private function receiveMessage(message:Object):void{
	write(message.user+": "+message.text);
private function write(txt:String):void{
	txtHistory.text += txt+"\n";

*Sequence: Very important thing - every different message must be unique, you can’t send same message twice. P2P rerouting mechanism will think it has already delivered that message - that’s why we are adding a sequence number - can be also random.

Step 6: Create UI

<s:TextArea left="10" right="10" top="10" bottom="40" id="txtHistory"/>
<s:TextInput x="10" id="txtUser" text="{user}" bottom="10"/>
<s:TextInput left="145" right="88" id="txtMessage" bottom="10" enter="sendMessage()"/>
<s:Button label="Send" click="sendMessage()" enabled="{connected}" bottom="10" right="10"/>

Step 7: Run it