Tech Kaizen: 3/1/10

Instant Messaging(IM)

Instant messaging (IM) is a form of real-time direct text-based communication between two or more people using shared clients. The text is conveyed via devices connected over a network such as the Internet.

ref:

Instant Messaging - http://en.wikipedia.org/wiki/Instant_messaging

Extensible Messaging and Presence Protocol(Jabber) - http://en.wikipedia.org/wiki/Jabber

Instant Messaging Protocols -

http://en.wikipedia.org/wiki/Comparison_of_instant_messaging_protocols

Pidgin (software) - http://en.wikipedia.org/wiki/Pidgin_(software)

A free chat client used by millions. Connect easily to MSN, Google Talk, Yahoo, AIM and other chat networks all at once

Pidgin (Source Code) - http://pidgin.im/download/source/

libpurple - http://developer.pidgin.im/wiki/WhatIsLibpurple

Libpurple has support for many commonly used instant messaging protocols, allowing the user to log into various different services from one application

SourceForge projects that use libpurple -

http://sourceforge.net/search/?type_of_search=soft&words=libpurple

Meebo - http://en.wikipedia.org/wiki/Meebo

Meebo is an instant messaging program which supports multiple IM services, including Yahoo! Messenger, Windows Live Messenger, AIM, ICQ, MySpaceIM, Facebook Chat, Jabber, Google Talk, Myyearbook IM and XMPP; it is based on the free and open source library libpurple created by the software developers of Pidgin

Miranda IM - http://en.wikipedia.org/wiki/Miranda_IM

Miranda IM is an open source multiprotocol instant messaging application, designed for Microsoft Windows. Miranda is free software distributed under GNU General Public License

Network Packet Filtering

Packet Filtering(PF) is all about controlling access to a network by analyzing the incoming and outgoing packets and letting them pass or halting them based on the IP addresses of the source and destination.

Packet filtering is the selective passing or blocking of data packets as they pass through a network interface. The criteria that pf uses when inspecting packets are based on the Layer 3 (IPv4 and IPv6) and Layer 4 (TCP, UDP, ICMP, and ICMPv6) headers. The most often used criteria are source and destination address, source and destination port, and protocol. Packet filtering is one technique, among many, for implementing security firewalls.

ref:

TCP/IP Protocol Stack - http://www.protocols.com/pbook/tcpip1.htm

Three ways to get your MAC address -

http://www.codeguru.com/cpp/i-n/network/networkinformation/article.php/c5451

How OSI works - http://computer.howstuffworks.com/osi1.htm

Packer Filtering Faq - http://www.openbsd.org/faq/pf/filter.html

Windows Filtering Platform -

http://msdn.microsoft.com/en-us/library/aa366510(VS.85).aspx

Network Filtering Articles articles by Jesús O -

http://www.programmerworld.net/personal/firewall.htm

Network Traffic Filtering -

http://www.ntkernel.com/w&p.php?id=14

http://www.codeguru.com/forum/showthread.php?t=286378

Application Layer Filtering (ALF): What is it and How does it Fit into your Security Plan -

http://www.windowsecurity.com/articles/Application_Layer_Filtering.html?printversion

How do I hook the TCP stack in Windows to sniff and modify packets?

http://stackoverflow.com/questions/695057/how-do-i-hook-the-tcp-stack-in-windows-to-sniff-and-modify-packets

Filter-Hook Drivers?

http://msdn.microsoft.com/en-us/library/aa504969.aspx

An Adventure: How to implement a Firewall-Hook Driver?

http://www.codeproject.com/KB/IP/FwHookDrv.aspx

Unraveling the Mysteries of Writing a Winsock 2 Layered Service Provider -

http://www.microsoft.com/msj/0599/LayeredService/LayeredService.aspx

A Little Sniffer that Uses WSA Sockets (Windows Sockets)

http://beta.codeproject.com/KB/winsdk/Sniffer.aspx?msg=2471244

Blocking and Non-Blocking Sockets - http://www.developerfusion.com/article/28/introduction-to-tcpip/8/

Socket overlapped I/O versus blocking/nonblocking mode - http://support.microsoft.com/kb/181611

Reusable Socket Server Class - http://www.developerfusion.com/article/2498/a-reusable-windows-socket-server-class/

Socket overlapped I/O versus blocking/nonblocking mode -

http://support.microsoft.com/kb/181611

Which I/O Strategy Should I Use?

http://tangentsoft.net/wskfaq/articles/io-strategies.html

List of Http Headers - http://en.wikipedia.org/wiki/List_of_HTTP_headers

Http Header Field Definitions –

http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html

http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.33

RFC1945 - Hypertext Transfer Protocol HTTP/1.0 - http://www.faqs.org/rfcs/rfc1945.html

HTTP: Hypertext Transfer Protocol (HTTP 1.1) –

http://www.javvin.com/protocolHTTP.html

http://www.javvin.com/protocol/rfc2616.pdf

Rex Swain's HTTP Viewer - http://www.rexswain.com/httpview.html

TCL Language(C/C++) Bindings

Tcl is able to quickly integrate a wide range of technologies, as well as to easily adapt to new technologies and changing end-user requirements. Therefore it is the integration platform of choice for increasing numbers of developers. TCL has in built Language Bindings for C/C++ languages.

Application invoking Tcl - An application(developed in c/c++) calling the Tcl interpreter
Tcl invoking Application - Tcl calling extensions(developed in c/c++)

Why extend Tcl?

Here are a few reasons:

1. To add domain-specific functionality to Tcl
2. To turn Tcl onto a "better Tcl" - or to support a different programming style
3. To interface the Tcl scripting environment to existing software libraries
4. To hide implementation details by providing only object code releases
5. To rewrite Tcl bottlenecks as C/C++ code for improved performance
6. As a way to incorporate Tcl in an existing body of C/C++ code
7. The last reason is actually the opposite of extending the Tcl environment - in this case, the Tcl interpreter becomes part of an existing application and activated when appropriate

How does a scripting language talk to an Application Language(C/C++)?

Scripting languages are built around a small parser that reads and executes statements on the fly as your program runs. Within the parser, there is a mechanism for executing commands or accessing variables. However, in order to access C functions and variables, it is necessary to tell the parser additional information such as the name of the function, what kind of arguments does it take, and what to do when it is called. Unfortunately, this process can be extremely tedious and technical. SWIG automates the process and allows you to forget about it. In any case, it's probably a good idea to know what's going on under the hood.

Wrapper functions

Suppose you have an ordinary C function like this:

int fact(int n)
{
if (n <= 1) return 1; else return n*fact(n-1); } In order to access this function from a scripting language, it is necessary to write a special "wrapper" function that serves as the glue between the scripting language and the underlying C function. A wrapper function must do three things :

1. Gather function arguments and make sure they are valid.
2. Call the C function.
3. Convert the return value into a form recognized by the scripting language.

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