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Monkey Talk Design and Implementation of Netmeeting-Based Network Service Using Socket Programming

Monkey Talk Design and Implementation of Netmeeting-Based Network Service Using Socket Programming. Speaker : 簡祥任　何政儒 Date : 2006.06.26 Est. Time : 20 minutes. UNIX Project (0936) 2006 Spring Department of CSIE, TungHai University. I NTRODUCTION. Server Daemon - MonkeyD MonkeyTalk Client

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Monkey Talk Design and Implementation of Netmeeting-Based Network Service Using Socket Programming

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  1. Monkey TalkDesign and Implementation of Netmeeting-Based Network Service Using Socket Programming Speaker : 簡祥任　何政儒 Date : 2006.06.26 Est. Time : 20 minutes UNIX Project (0936) 2006 Spring Department of CSIE, TungHai University

  2. INTRODUCTION • Server Daemon - MonkeyD • MonkeyTalk Client • Command Line Interface (CLI) Version • Graphic User Interface (GUI) Version

  3. INTRODUCTION • Server Daemon • Run in background (daemon mode) or foreground (verbose mode) • Log events • Provide chatting environment • Accept connection • Collect users’ data • Handle request from client • Broadcast messages

  4. INTRODUCTION • Client – CLI • Interpret user commands • QUIT, HELP, etc. • Connect to host • Using TCP Socket and IPv4 Protocol • Resolve domain name (lookup DNS) • Open new chat room • Join a opened chat room • Chat in room

  5. INTRODUCTION • Client – GUI • Provide the same functions as CLI version does • Construct graphic interfaces using Qt library

  6. INTRODUCTION • Development Environment • Operating System • Fedora 3 (kernel 2.6.8) • Mandrake Linux 10.0 (kernel 2.6.3) • Window Environment • Provided by XFree86 via X11R6 protocol • Window Manager: KDE 3.2 • Compilation • GNU Compiler Collection (3.3.2) with thread support • Trolltech Qt Library (3.2.3) and Qmake utility (1.06c)

  7. INTRODUCTION • Operating System Dependents • TCP Module • achieve the communication between server and clients • Qt Library / X11 Server • Construct GUI • Pthread Library

  8. DESIGN • Key Methodologies • Application-Layer Protocol • Multi-Threading • States Transition and Control • Qt Programming

  9. Application-Layer Protocol • Language that server and clients talks • The interactions between server and clients are achieved by sending messages • One message is a string of ASCII characters in variable length and ends up with a new-line character (ASCII=13) • Composed of two fields: OPCODE and ARGUMENT • OPCODE • fixed length with four characters • specify which command is in use • ARGUMENT • variable length • may be absent in some commands

  10. Application-Layer Protocol • Three formats of message • No ARGUMENT • Single ARGUMENT • Multiple ARGUMENT • arguments are separated by a colon character “:”

  11. Application-Layer Protocol • We’ve designed sixteen commands for different purposes

  12. Application-Layer Protocol • Example • ULST: client request list of all users • UADD: server return information of online users Client: ULSTServer: UADD 0:John:1:Room#1Server: UADD 1:Tom:2:Room#2Server: UADD 2:Sam:2:Room#2Server: UADD

  13. Multi-Threading • Server process… • Serve many clients via different connections simultaneously • How about using fork() to fork folks to serve each client? • Unfortunately, fork() is a slow system call and IPC (shared-memory) of spawned process consume much resource • Send messages while receiving message • Process got blocked after calling read() – blocked I/O system call • Can be solved by replacing with non-blocked I/O system calls or threading • Client process… • Receiving command from user and message from host at the same time

  14. Multi-Threading • Threading Model • Client threads • BananaEater • Receive message • BananaFeeder • get input from user • send messages • Server threads • Main thread • accept connections • create new user • Pair of BananaEater and BananaFeeder for each client

  15. Multi-Threading • Broadcast messages • Server main thread • create user profile when new connection has established • MesgIndex, one of the fields in user profile, contains the index of next message to be sent in queue • Server BananaEater thread • initialize MesgIndex when client has entered room • insert received message to message queue • Server BananaFeeder thread • check if the value of MesgIndex is equal to current index of message queue on a regular basis (busy polling) • send new arrival message to client and increase MesgIndex by one while MesgIndex is not equal to current index

  16. Multi-Threading • Broadcast messages • User entered Room#2

  17. Multi-Threading • Broadcast messages • New message has arrived

  18. Multi-Threading • Broadcast messages • BananaFeeder send new message to user and update MesgIndex

  19. Multi-Threading • Race Conditions • Occurs in server process • Threads write and read to shared data in race • Consistence of data could be damaged in such situation • Solution: Using mutual exclusive (MUTEX) lock to protect shared data • Call pthread_mutex_lock() before accessing shared data • Call pthread_mutex_unlock later • Threads never access to shared data in chorus

  20. State Transition and Control • Flow Control • Server and client process should handle improper use of commands • Ex. Client send ULST before NICK • Ex. User use EXIT command before connecting to host • Fifteen states has been defined

  21. State Transition and Control

  22. Qt Programming • Client – GUI Version • Use Qt library to construct graphical interface • Developed by using Qt Designer • Each “window” has own class, derived from QWidget • Events are caught and handled by signal-slot mechanism • All events handling written in <main.cpp>

  23. Qt Programming

  24. Qt概論 • 以C++為基礎所開發針對GUI設計的程式函式庫 • 能使用Qt Designer輕鬆設計出介面，或自己撰寫程式。

  25. Qt Object Model • signals and slots • object properties • events and event filters • contextual string translation for internationalization • sophisticated interval driven timers • object trees • guarded pointers, QGuardedPtr

  26. Object Properties • 分為Q_PROPERTY和Q_OVERRIDE，繼承至QObject • Q_PROPERTY ： // QButton *b and QObject *o point to the same button b->setDown( TRUE ); o->setProperty( "down", TRUE ); • 提升compile time的效能

  27. Events and Event Filters • events是一個物件繼承至QEvent， 例如：QPaintEvent、QMouseEvent、QKeyEvent等 • QObject::installEventFilter()：用於外部event的參考

  28. Signals and Slots • Signals：當object想改變內部狀態時所發出的一種訊息，就是signal， Ex：JPushButton中的clicked()。 • Slots： 只有當signal connected被發出時，才會被使用，是一種C++ functions。 • Ex： connect(&a, SIGNAL(clicked()), &b, SLOT(clear( ));

  29. Qt 運作原理 • Qt 是屬於多平台型的函式庫 • Ex：X11

  30. 實做 • Qt Designer ：

  31. Qt Programming • References • Official online documentation • http://doc.trolltech.com/3.3/ • Qt 3.3 Whitepaper, Trolltech • C++ GUI Programming with Qt 3 • By Jasmin Blanchette, Mark Summerfield, Prentice Hall • Free to download now! • Programming with Qt • By Matthias Kalle Dalheimer 2nd edition, O'Reilly Media

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