CComet

CComet is a tiny Comet based on EventServer and it is developed and maintained by Yulong Tian. To be specific, CComet uses the http module provided by EventServer.

Comet is a technology for push-notification server. It allows a web server to push data to a browser through HTTP protocal. In other atomsphere, such as android and windows phone, it can behaves GCM and MPNS.

CComet can be used as the messaging server of many applications. To demonstrate the use of the library, I have provided a webchat demo in this project. In future, I will also provide sdks for android and windows phone apps.

Our work is mainly inspired by icomet and I have taken many interesting idea from ideawu, both from blogs and source code. Thanks for ideawu. Thanks again for OSC (Open Source Community).

Usage

1. Start the server.

git clone https://github.com/mathetian/CComet
cd CComet
make ccomet
cd bin
./comet

And run the web-demo in directory demo/web/

2. Run the chat demo

1. Compile and start ccomet server
2. Drag and drop the file demos/web/chat.html into one web browser
3. Drag and drop the file demos/web/chat.html into another different web browser
4. Start chatting!

Client API

We provide a client api of javascript in CComet.

function CComet(config)
{
	var self = this;
	var sign_sta = false;
	self.seqid = 0;
	self.sub_url  = config.sub_url;
	self.pub_url  = config.pub_url;
	self.sign_url = config.sign_url;
	self.callback = config.callback;

	self.sign = function(){
	    /// For detail information, please seek for the ccomet.js
	}

	self.sub = function(){
	    /// For detail information, please seek for the ccomet.js
	}
	
	self.pub = function(content){
	    /// For detail information, please seek for the ccomet.js
	}

	self.sign();
}

Performance

CComet   :   version 1.0
Date     :   Sunday June 20 20:24:47 2014
CPU      :   4 * Intel(R) Core(TM) i5-3317U CPU @ 1.70GHz
CPUCache :   3072 KB
G++      :   4.8.1
Demux    :   EPoll
Phy-Mem  :   3888 MB

In the benchmark of EventServer, we have found out the QPS and the memory cost of each connection of http module. We will discuss the cost of memory when we add a layer of ccomet.

Connections	VIRT	RES
0	24M	8M
10000	33M	10M
50000	60M	36M
100000	106M	81M
200000	210M	162M

0.92 KB per connection ?

Discussion : Through our experiments, we have proved the stability of our system.

Design Principle

1. Use jsonp to solve CORS which is short for Cross-Origin Resource Sharing, problems.
2. Long-polling instead of polling. To solve some problem in jsonp, I use a timeout 30 seconds, which is a reasonable value, in produce mode.
3. Compared with icomet, I remove authetication flow and support for iframe technology.

CComet UML Graph

Role in Produce Atmosphere

License

This client is licensed under the same license as EventServer. And this license will be restricted by the license of icomet.

Todo List

1. Android & Windows Phone 8
2. Memory Pool
3. ...