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COLLABORATION GROUPWARE FOR MOBILE DEVICES USINTG THE
MICROSOFT.NET COMPACT FRAMEWORK
MIHIR P. PATEL
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF ENGINEERING
UNIVERSITY OF FLORIDA
Mihir P. Patel
I would like to sincerely thank Dr. Sumi Helal for his guidance and advice
throughout the course of this proj ect. I would also like to thank the other two members of
my committee, Dr. Chris Jermaine and Dr. Baba Vemuri for their time and assistance.
I would also like to thank Harris Corporation for providing the nicely equipped
Mobile Computing Lab. I would like to thank John Bowers, Denise Atteberry, Timothy
Heffernan III and Kevin Austin for their help during my academic career.
Finally I would also like to thank my parents, sister and my flance for their love
and support throughout my academic career.
TABLE OF CONTENTS
LI ST OF T ABLE S ........._.. ........_. .............. vi...
LIST OF FIGURES .............. ....................vii
AB STRAC T ................ .............. ix
1 INTRODUCTION ................. ...............1.......... ......
1.1 Thesis Objectives............... ...............
1.2 Structure of the Thesis............... ...............3.
2 OVERVIEW OF AD-HOC MOBILE COLLABORATION ................. ................. .5
2.1 Microsoft Net Meeting 3.0 .............. ...............5.....
2.2 YCab JAVA ................. ...............6................
2.3 YCab.NET ..................... ..... .............
2.4 Multihop Ad-hoc Instant Messaging .............. ...............7.....
3 DESIGN AND ARCHITECTURE OF YCAB.NET CF............... ...................1
3.1 Connection Management Layer. .....__.....___ .........._ ...........1
3.2 Service Layer .............. ......_ ...............14..
3.2. 1 Shared Whiteboard ............. ..... __ ...............16.
3.2.2 Text chat service............... ...............19
3.2.3 Audio Chat Service............... ...............20
3.2.4 View peers ............ .... __ ...............21.
3.2.5 File Transfer Service .............. ...............22....
3.2.6 Shared Image Service ............. ....._ ...............23.
3.3 Client Management Layer .............. ...............24....
3.3.1 Client M manager ............. ..... ...............24.
3.3.2 Client Frame .............. ...............24....
3.3.3 M message Router .............. ...............25....
3.3.3 Obj ect Rebuilder. ............ _...... ._ ...............25.
3.3.4 Packet Filter ............... .... ._ ...............26..
3.4 Communication Management Layer .............. ...............27....
3.5 Data Transfer Layer ................. ...............28...............
3.6 YCab.net CF Server ............. ...... .__ ...............29
3.6.1 Central Storage of Messages .............. ...............29....
3.6.2 M ain Server .............. ...............30....
3.6.3 Server Thread .............. ...............31....
3.6.4 M message Reader ............ _. ..... ............... 1...
3.6.5 M message W riter. ............ _. ..... ............... 1.
4 DEVELOPMENT USINTG YCAB.NET CF ......____ ...... .. .........._.......3
4.1 Design Specifications .............. ...............33....
4.2 Loading YCab.net CF ............_...... .__ ...............34.
4.3 Creating a Custom Service .............. ...............34....
4.4 Setting the Namespace............... ...............3
4.5 Setting Inheritance ............ ..... ._ ...............36..
4.6 Implemented SharedColor Class .............. ...............37....
4.7 Handling User Input .............. ...............37....
4.8 Processing Incoming Messages .............. ...............39....
4.9 Compiling and Deploying............... ...............4
4.10 Output .............. ...............42....
5 CONCLUSION AND FUTURE WORK .............. ...............43....
5.1 YCab.net CF Server ................. ...............44........ ...
5.2 Security ................. ...............44....... .....
5.3 New Services .............. ...............44....
LIST OF REFERENCES ............ ............ ...............46...
BIOGRAPHICAL SKETCH .............. ...............48....
LIST OF TABLES
2.1 Comparison of different collaborative software packages ................. ................ ...9
2.2 Description of software components used in YCab.net CF .............. ...................10
2.3 Description of hardware components used in YCab.net CF ................. ................1 1
LIST OF FIGURES
2.1 Microsoft Net Meeting 3.0 ............_...... .__ ...............5..
2.2 YCab Java Sample Application............... ...............
2.3 YCab.NET Application ............ ..... ._ ...............7...
2.4 Multihop Ad-hoc Instant Messenger ................. ...............8............ ...
3.1 Layered architecture of YCab.net CF ................. ...............13........... ..
3.2 Connection screen for sample application .............. ...............14....
3.3 Application without any services (left) and list of built-in services (right) .............15
3.4 Shared Whiteboard service in YCab.net CF .............. ...............16....
3.5 Whiteboard as a 2 dimensional array (left) and derivation of x and y coordinates
from the compressed form (right) .............. ...............18....
3.6 Text chat service in YCab.net CF .............. ...............19....
3.7 Voice chat service .............. ...............20....
3.8 File Transfer service............... ...............22
3.9 Shared Image service .............. ...............23....
3.10 Network mode selection during startup .............. ...............28....
4.1 Error detecting feature in Visual Studio.NET 2003 .............. .....................3
4.2 Adding a new class to the proj ect. ....__ ......_____ .......___ .........3
4.3 Design view of the SharedColor service ....__ ......_____ ..... ....___........3
4.4 Setting proper namespaces ............_...... .__ ...............36...
4.5 Setting proper inheritance .............. ...............36....
4.6 Constructor of SharedColor class............... ...............37.
4.7 Adding an event handler .............. ...............38....
4.8 Implementation of the event handler for SharedColor service. .............. ..............39
4.9 Implementation of processMessage ................. .......__....................._..40
4.10 Adding the new service to the Client Frame ..........._.._ ....._. ........_........41
4.11 SharedColor automatically added to the main menu .............. ....................4
4.12 Initial screen of SharedColor (left), SharedColor screen after one event ..............42
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Engineering
YCAB.NET CF: COLLABORATION GROUPWARE
FOR MOBILE DEVICES USINTG THE
MICROSOFT.NET COMPACT FRAMEWORK
Mihir P. Patel
Chair: Abdelsalam (Sumi) Helal
Maj or Department: Computer and Information Science and Engineering
Today more and more people are using mobile devices such as handheld Personal
Digital Assistants (PDAs), cellular phones, smart watches, etc. The phrase "mobile
device" can be interpreted in many different ways. A laptop can be considered a mobile
device, but a handheld PC or a cellular phone is a truly portable mobile device. These
mobile devices are getting popular because they allow people to stay in touch with their
friends, family, and business associates.
The new mobile devices support very specific collaborative applications, but there
is a lack of an open standard or even a framework that would allow the development of
collaborative applications for these small mobile devices. This thesis is focused on the
development of one such framework called YCab.net CF Wireless Collaboration using
Microsoft .NET Compact Framework. YCab stands for Wireless Collaboration. The
previous versions of YCab did not support development for mobile devices. This thesis
proposes the newest version of the YCab project. This framework provides an API,
which can be used to develop applications for PDAs running Microsoft Pocket PC
operating system and cellular phones running Microsoft SmartPhone operating system.
This thesis is not just about re-implementing the YCab architecture for small
mobile devices, but about implementing a new customized version of YCab, which is
optimized in terms of memory and processing power. Also the new YCab
implementation needed to be compact enough to fit on the mobile devices, yet powerful
and robust enough to support all the services that were included in the desktop versions
of YCab i.e., YCab Java and YCab.NET.
Mobile devices are growing in terms of popularity in today's market. The key
feature that is pushing the sales in mobile devices is the wireless technology built-in the
devices. With the wireless connectivity these mobile devices can be used for personal and
business use to access the internet. The small mobile devices with wireless connectivity
cab also be used to keep in touch with friends, family and business clients through
Most of the software applications that are available for these devices are developed
focusing on a particular need of the customer. For example, an application that allows a
Hield engineer to take a picture of some construction site and send it to the main office is
different then an application that allows a group of friends to keep in touch by sending
text messages on their mobile devices. Thus all the collaborative applications that are
available today are too specific, so there is need for a software package that allows a
virtual space for collaboration on mobile devices. This virtual space can then be tailored
to satisfy specific needs. Such a software package can not be an application, because an
application can not be generic. Also an application can not be very flexible and
extensible. This thesis discusses the design and architecture of a software package -
YCab.net CF that facilitates the creation of an ideal virtual space, which can be tailored
to specific needs.
YCab.net CF is not an application, but is a basic framework that is implemented in
form of an Application Programming Interface (API). YCab stands for Wireless
Collaboration. Lee  and Buszko  first developed such a framework YCab Java -
using Sun Microsystems's Java programming language. Applications developed using
YCab Java can be used only on computers that had a Java Virtual Machine installed on
them. Second framework was developed by Procopio  using the Microsoft .NET
Framework. The framework which was called YCab.NET can be used to develop
applications for any computer that runs any version of Microsoft Windows operating
system. Both YCab Java and YCab.NET could be used to develop collaborative
applications for desktop or laptops PCs, but there still was a need for a framework that
would facilitate application development on handheld PCs and cellular phones. This
thesis proposes the newest version of YCab proj ect.
This thesis involved unique problems. With the devices getting smaller and smaller,
so does their processing speed and internal memory. Also the programming environment
gets limited. The complex programming structures and designs that are normally
available on non-portable computers have to be built using only the simple structures
available on these small mobile portable devices. For example the "Binary Serialization"
(allows complex obj ects to be exchanged between different machines without any special
effort) capability available on desktop PCs is not available on the handheld mobile
devices, so special arrangements were made to exchange obj ects in YCab.net CF. Thus
this thesis is not just about re-implementing the YCab architecture for small devices, but
redesigning and adapting a new customized version of YCab which is optimized in terms
of memory and processing power. Also the new YCab implementation needed to be
compact enough to fit on the mobile devices, yet powerful and robust enough to support
all the services that were included in the desktop versions of YCab i.e., YCab Java and
1.1 Thesis Objectives
The primary obj ective of this thesis is to design and implement a framework that
will allow developers to create highly robust and optimized collaborative applications
that can be used on PDAs running Microsoft Pocket PC operating system. Also develop
built-in collaborative services such as shared whiteboard, text chat, shared files, shared
image, voice chat and awareness. The proj ect goals can be summarized by the following.
* Design and implement the YCab framework that could be supported on Pocket PCs
* Develop services that are available in the previous versions of YCab.
* Develop new services to enhance the user experience.
* Implement the framework using the features that are also supported on the cellular
phones with SmartPhone operating system, so that the same framework can be used
on cellular phones.
* Develop a sample application using YCab.net CF and document the API in a user-
1.2 Structure of the Thesis
This thesis has a total of five chapters. Chapter 1 comprises of the introduction and
the motivation behind developing YCab.net CF API. Also Chapter 1 presents the history
of the YCab proj ect and shows the roadmap that lead to the development of YCab.net
Chapter 2 briefly describes some of the proj ects that focused on the issue of Ad-hoc
mobile collaboration. Finally Chapter 2 describes the main technologies (hardware and
software) used in YCab.net CF proj ect.
Chapter 3 describes the design and architecture of the YCab.net CF framework.
Further this chapter describes the implementation and function of each of the layers in the
YCab.net CF framework.
Chapter 4 is targeted mainly towards the users of the YCab.net CF. This chapter
step-by-step illustrates how a sample application can be built using the API.
Chapter 5 concludes this thesis and also mentions how YCab.net CF can be
improved by implementing more user services. Also this chapter suggests some
improvements in the current architecture.
OVERVIEW OF AD-HOC MOBILE COLLABORATION
This section describes the proj ects that have focused on the issues of mobile
1. Microsoft Net Meeting 3.0 at Microsoft Corporation.
2. YCab Java at the University of Florida
3. YCab.NET C# at the University of Florida
4. Multihop Ad Hoc Instant Messaging at Virginia Tech.
2.1 Microsoft Net Meeting 3.0
Net meeting is software developed by Microsoft Corporation. Net meeting is
included in Windows Operating System 2000 and later by default. Net meeting is only
supported by desktops running Windows operating system. Also it is based on a
centralized architecture. The user has to first connect to a Microsoft net meeting server by
using a registered user-id and password. Then the user can invite other people to join the
collaboration by selecting their user-ids. Net meeting is not supported by any hand-held
device (PDA, Smart phone, etc) other than a light weight laptop.
Figure~~0 2.1 M icrsof Ne eeig.
2.2 YCab JAVA
YCab is a framework and API designed specifically for supporting rapid
collaborative-application development. YCab API is written in Sun Microsystems's
JAVA programming language. The application developed using YCab API allows mobile
collaboration in Ad-Hoc environments. The application that uses YCab API runs using
the Java Virtual Machine, so the application is only supported on the platforms that have
a Java Virtual Machine. As almost no PDA or Smart phone as of today support the full
version of the JAVA, such an application can not be used on any PDA or Smart phone.
The YCab framework and API are thoroughly described in thesis by Lee  and Buszko
, and is summarized in a journal paper by Lee, Buszko, and Helal . The YCab
proj ect is therefore only briefly covered here. Below is a screen shot of a running
application developed using YCab API.
Figure 2.2 YCab Java Sample Application 
The main goal of YCab.NET proj ect was to port the original YCab from Java to
Microsoft C# to utilize the managed and robust runtime and rapid application
development environment of Microsoft .NET Framework. The long term goal of this
proj ect was to have YCab.NET run on PDAs running Windows CE, Pocket PC or
SmartPhone operating systems. This proj ect not only translated the code from Java to C#
but also added numerous new features to the original YCab API. In YCab.NET the user
interface was redesigned to give the application a commercial look. YCab.NET added
streaming audio and improved support for file transfers. Over all the application
developed with YCab.NET was very user-friendly.
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Microsoft Pocket PC operating system. The main goal of this proj ect was to develop an
application which allowed people with Pocket PCs to chat with each other in an ad-hoc
environment. Whenever a user with a Pocket PC walks into the ad hoc environment, a
"buddy" list similar to that in MSN Messenger's Instant Messaging pops up and the user
can chat online with his/her buddies in the infrastructure-less ad hoc network. The proj ect
was implemented using Microsoft .Net Compact Framework@ and C#9 programming
language, as well as Microsoft Smart Device Extension@ for the .Net platform.
cha~r)b YMI i~gt~t?
B 1 1141,
~Cll~t I I Bm I
Figure 2.4 Multihop Ad-hoc Instant Messenger 
~ar: E~dbr'r ]~if~m;rt~xl;
Microsoft Net YCab Java YCab.NET Multihop Ad
Meeting Hoc Instant
Supported Microsoft Any Microsoft Microsoft
Operating Windows 95 Windows 95 Pocket PC
System or newer or newer 2002 or newer
Hardware Desktop PC Desktop or laptop Desktop PC or PDA with
Requirements or laptop PC computer laptop PC Pocket PC
Special Software None Sun Microsoft Microsoft
Requirements Microsystems's .NET .NET Compact
Java Virtual Framework Framework
Centralized YES NO NO NO
Support for Ad NO YES YES YES
Text messaging YES YES YES YES
Multimedia YES YES YES NO
Extensible NO YES YES NO
Table 2. 1 Comparison of different collaborative software packages
Table 2.2 Description of software components used in YCab.net CF
Microsoft Visual Studio.net 2003 is a
very rich Interactive Development
Environment that allows the developers to edit,
compile, debug and execute code all in one
place. Also it has built-in support for Smart
Device Extensions, which allows developers to
develop applications for mobile devices such as
PDAs and cellular phones.
The .NET Compact Framework consists
of the base class libraries and has a few
additional libraries that are specific to mobility
and device development. The Framework runs
on a high performance JIT Compiler. The
Common Language Runtime is built from the
ground up to be specific to the .NET Compact
Framework so that it runs more efficiently on
Visual Studio.net 2003
.net Compact Framework
.. n Compaq Ipaq 3800 is a handheld PC
running Microsoft Pocket PC 2002
operating system. It has built-in stereo
speakers and a microphone. Its is powered
by Intel 206 MHz StrongARM processor.
Compaq Ipaq 3800
The dual-slot PC card expansion
pack allows the user to use PC cards such
as wireless network adapters, extra storage
and battery packs. In this proj ect the
expansion pack was merely used for the
Dual expansion pack for Ipaq wireless adapter.
The Linksys wireless network
adapter ver 3.0 provides the capability of
using the wireless network in infrastructure
and ad-hoc mode. It also come with a
Linkys ireess ardver3.0 software utility for Pocket PC OS.
Table 2.3 Description of hardware components used in YCab.net CF
DESIGN AND ARCHITECTURE OF YCAB.NET CF
YCab.NET CF is a framework and API that allows software developers to create
collaborative applications that harnesses the power of Microsoft .NET Compact
Framework (.NET CF). These applications can be used on any device that supports .NET
CF. This chapter will discuss the implementation of the framework and the sample
An application developed using YCab.NET CF has different services. A "Service"
in YCab.NET CF is a custom built application that is a part of the main application. All
services together make the application a true collaborative space. From a .NET
programmer' s perspective a service in YCab.NET CF is a subclass of
System.Windows.Forms.Form. The class "Service" is implemented in the API. The
service class contains all the common GUI components that all the services need like the
main menu that contains names of all services and the "exit" option to close the
application. This base class also contains the button that will display the contents of the
help file associated with the service. The Service class provides a high-level abstraction
to the application developer by hiding all the low level implementation details and the
calls to the lower levels in the API. The API can be divided into a layered structure as
shown in figure 3.1. The layers that are enclosed by the dotted line form the core of the
architecture. The service layer that lies outside of the dotted line is the application layer.
The service layer is formed of customizable components called services. There are built-
in services in this layer to which new custom services can also be added.
CONNECTI ON "' "' '"''"' ""
COMMUNICATION MANAGOEMENTT LAYER I
ii ODATA TRANSFER LAYER
Figure 3.1 Layered architecture of YCab.net CF
3.1 Connection Management Layer
This is the very first layer in the YCab.net CF architecture. This layer has
components that deal only with getting the user to connect into the virtual collaboration
space. The main class that handles most of the work related to the connection is the
Connection Manager. When the sample application provided with YCab.net CF API
starts, the screen shown in Figure 3.2 is displayed. Once the user clicks on the "Connect"
button, all the information the user fills out in the form is sent to the connection manager.
The connection manager at this point starts a timer that times out after certain seconds.
Then the connection manager sends this information to all the collaborators currently
present in the collaboration.
Figure 3.2 Connection screen for sample application
If any of the collaborators is using the same userid, then that particular collaborator
will send a message to the new user who is trying to get connected. When the new user
receives such a message, the connection manager will display the above shown screen
again with the message "Userid in use, please select another userid". If the timer that the
connection manager started times out and the new user does not receive any message,
then the control of the application is forwarded to the lower layer in the API i.e., the
service layer. Once successfully connected, all the available services are displayed in the
main menu of the application. The user can chose any service and start collaborating with
3.2 Service Layer
This layer contains all the services. There are two maj or types of services. The first
one is the system level services. The system level services are the ones that are absolutely
needed by the application to run effectively. An example of such a service is the
connection service that allows the user to connect to his/her peers. Another example is
the awareness service; this service allows the user to view the list of peers involved in the
collaboration. If this service stops working then, there is no way for the user to know if
his/her peer is not replying or he/she is not in the wireless network range( i.e., has lost
connection). The other maj or type of service is the user level service. These are the
services that the user interacts with the most. Examples of this type of services are the
text chat service, shared image service, file transfer service, etc. These services improve
the value of the application by providing different ways to collaborate with peers. All the
services inherit from the base class "Service". This class abstracts the implementation
details that involve communicating with the lower level classes in the API such as the
Client Manager, Message Router, Packet Filter, etc. The following figure shows the
application that is started without initializing any of the services.
Audio chat riImagde
File Services Help I File 1Services Help M
Figure 3.3 Application without any services (left) and list of built-in services (right)
There are a number of built-in services in the YCAB.NET CF API which are
described in the following sections. The service layer is formed of the following services.
3.2.1 Shared Whiteboard
Let us say we have Bob, John and Jane in a collaboration space created by an
application developed from YCab.NET CF and this application has the shared whiteboard
service. This service provides a virtual whiteboard, where each of the collaborators Bob,
John and Jane are allowed to draw, erase and clear the whiteboard. Let us say Bob
chooses the color of the pen from the drop down menu and starts drawing on the
whiteboard. The moment he pushes down his stylus on the Pocket PC screen, the service
starts capturing the movement of the stylus in form of x and y coordinates. Once Bob is
finished drawing and lifts the stylus off the screen, a message containing the captured x
and y coordinates and the color of the pen Bob used is sent to John and Jane. Once the
message is received on John and Jane's side, the service will use the x and y coordinates
and the color of the
File Services Help
Figure 3.4 Shared Whiteboard service in YCab.net CF
pen specified in the message to recreate the drawing that Bob drew on his Pocket PC.
Now let us say Jane wants to add something to Bob's drawing, she can pick a different
colored pen and draw on her Pocket PC. Once again the service will send the x and y
coordinates that forms Jane' s drawing and the color of her pen and sends them to Bob
and John. Now let us say John wants to clear the whiteboard and start over, he can use
the button labeled "Clear" and once again a message will be sent. But this time a special
message will be sent. Once the message is received on Jane and Bob's Pocket PC, the
service will identify the special message and clear the whiteboard. Thus this service
provides a truly shared whiteboard, where the collaborators can express their ideas by
drawing on the whiteboard just as in real meetings.
To have a real shared whiteboard, instead of sending the state of the whiteboard
after every change to all the peers, this service only sends the change in the state of the
whiteboard. To further optimize the size of the message sent after every change the
following steps were taken. The x and y coordinates of the position of the stylus are of
type "int" in C#, which takes 4 bytes each. So to send one line which is formed of two
points, we need to send 4 integers which would take 16 bytes total. The drawing area on
the screen is limited to 200 X 200 pixels, where pixel 0 is in the top left of the drawing
area. Now the drawing area can be mapped into a two dimensional array with x and y
coordinate as the indices in the array. Further a two dimensional array can be represented
as a one dimensional array. The following example illustrates the optimization of the
message sent by the "Shared Whiteboard" service. Let us say that the table shown in the
next figure represents the whiteboard. Now each cell in the table is a pixel in the
O 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
20 21 22 23 24 25 26 27 28 29 glig 35 3 7 38 3
40 41 42 4748 49 50 51 52 53 54 55 56 57 58 59
380 -- 399
If (pl < 201)
xt (pl == 2oo)
pix = o;
pix = pl;
ply = O;
plx = pl % 200;
ply = (Int) (pl/200);
whiteboard, so the table represents a whiteboard of size 20 X 20 pixels. The orange line
starts from the point (1,2) and ends at (15,0)
a(1,2) = 2 20 + 1 = 41
b(15,0) = 0* 20 + 15 = 15
Thus, the orange line can be represented with two integers 41 and 15 instead of two
points with two integers for each point. On the other side the two points are derived using
the following algorithm where pl represents the point that is being derived.
Figure 3.5 Whiteboard as a 2 dimensional array (left) and derivation of x and y
coordinates from the compressed form (right)
I Hihr H
File Services Help E
History of messages
Enter message here
3.2.2 Text chat service
Text chat service allows the collaborators to send text messages to each other. First
the user enters the message in a text box using any of the text input mechanisms available
on the mobile device, and then clicks on the send button. Once the user clicks the send
button, an array of bytes is instantiated with the American Standard Code for Information
Interchange (ASCII) encoded text message as its content. The message array along with
the user' s userid is then forwarded to the user manager and then to the lower levels in the
API and finally into the wireless network. Upon receipt of such a message from the
network, the text-chat service will first decode the byte array called message using the
ASCII standards and display it in the text-box labeled "History" in figure 3.6 along with
the sender' s userid. This service could be easily extended to include private message. For
example, if there are five collaborators and userl wants to send a private message to
user2, then userl can write the message that starts with special character sequence
Figure 3.6 Text chat service in YCab.net CF
followed by the receiver' s userid/s. Upon receipt of such a message if the receiver of the
message is not same as the user' s name, then the message is not displayed in the "History
of messages" (see figure 3.6) and thus the message stays confidential.
3.2.3 Audio Chat Service
This service allows the collaborators to send and receive voice messages to/from
each other. When the user clicks on the button labeled "Talk," voice recording starts. At
this time, the user can start talking. Also right after the talk button is clicked, a floating
GUI component is displayed, which has a button labeled "OK." Once the user is done
talking, he/she can click on the "OK" button on the floating GUI component. Once the
"OK" button is clicked the floating GUI component is hidden. All the data
corresponding to the voice message are then used to generate a fie with extension "way."
WAVE fie format is very simple. WAVE Hiles contain the raw PCM Pulse Code
Modulated audio data. This Eile format does not use any compression. Once the wave
Eile is created, it is sent to the lower layers of the API for transmission. Once the file is
STalk Mute Ta Ilk Mlite
Press OK to stoo
File Services Help File Services Help
Figure 3.7 Voice chat service
received on the other user' s application, the sound file is played. A text message is also
displayed with the sender's userid, so that everyone can see who sent the voice message.
Whenever the recording or playback of a voice message is completed the Hiles containing
the message is always deleted to preserve memory on the user' s machine.
3.2.4 View peers
This service allows every collaborator to view the userid of every other
collaborator. Also this service can be easily extended to display other information for
each user i.e., first name, last name, a head-shot, etc. This service at all times maintains a
hash-table data structure. Each entry in this hash-table is a pair of userid and a timestamp.
The timestamp is just an integer which is initialized to zero in the beginning. This service
periodically sends out a special message called a ping-message. This message contains all
the information about the user i.e., userid, first name, last name, etc. Once this
information is received on the other users' mobile device, this service checks if sender' s
information is already present in the hash-table. If the info is not present, then it is added
to the hash-table along with the sender' s userid with the current timestamp. If the
information is already present in the hash-table, then the timestamp associated with the
sender' s userid is updated. Every time a message is received, the timestamp is increased
by 1. After a certain timeout period, the hash-table is cleaned up by removing userids that
have a very old timestamp. A "Very old timestamp" is defined by an integer constant
which is set to 50. Thus after receiving 50 messages, the hash-table is cleaned up to
reflect the absence of collaborators who got disconnected due to network unavailability
or left the collaboration space voluntarily.
File Path Sender
\Program Files\Y~ab.Net... Sumi
\Program Files\Y~ab.Net... Mihir
\Program Files\Y~ab.Net... Mihir
\Program Files\Y~ab.Net... Sumi
\IProgram Files\Y~~ab.Net... Sumi
\IProgram Files\Y~~ab.Net... Mihir
Fle:All Folders C dnlcel
Type: I ~
Name r I Date ISize
Blank Docu... 9/3 12:... Ob
[Blank Note 9/3 12:... Ob
~calccurrency F 6/14 1:... 886b
~cf F 6/7 7:4... 484b
~chooser_n... F 6/7 7:4... 1.O0k
~choosergprey F 6/7 7:4... 1,00' ;
Elick to semi a file
File Services Help E -
3.2.5 File Transfer Service
The File-Transfer service allows the collaborators to share files. This service
provides each user the capability to send out a file to other peers, and also to receive files
from them. To send a file, the user should click on the button labeled "Click to send a
file", which opens up the user' s "My Documents" folder. Now the user can select the file
that he/she wants to send by just clicking on the file name. Once the user selects the file,
the file is read into a byte array and sent down to the lower layers of the YCAB.NET CF
API for transmission. Once the file is received on all the other user' s mobile device, it is
added to the list of received file as shown in figure 3.8. This service can be extended by
allowing the user to view the file from the received files by clicking on it. Also one of the
limitations of this service is that the files that are to be sent out should be under the "My
Documents" folder. This limitation is inherited from the underlying .NET Compact
Figure 3.8 File Transfer service
Folder: IAll Folders TI Edn~cel
Type: Irnages (*.jpg *.jpeg, *.gif, *.
text hat 3117:...10
rrI ~111 -.-n--
Click to sendr anl image
File Services Help E *
3.2.6 Shared Image Service
The Shared-Image service allows the collaborators to share an image. Any of the
collaborators can post an image on this virtually shared space. At any given time, all the
collaborators will see the exact same image. To post an image on this virtual "wall", the
user will first click on the button labeled "Click to send an image". Once the user clicks
on the button, the user will be asked to choose an image from the list of the images stored
under the "My Documents" folder on the user' s mobile device. The user can select the
image by clicking on it. As soon as the user selects the image, the image Eile will be read
into a byte array and sent down to the lower layers of the API for transmission. Once the
Eile is received on the other user' s mobile device, the image will be displayed on the
screen. If an invalid image file or corrupted Eile is received, then an error message will be
displayed letting the user know the name of the sender who sent the invalid image Eile.
Figure 3.9 Shared Image service
This service is very close to the File-Transfer service in terms of implementation. Just
like the File-Transfer service, this service also has a limitation that the image files to be
sent out should reside under "My Documents" folder on the sender's mobile device.
3.3 Client Management Layer
As the name suggests, this layer is responsible for managing the user/client' s state
in collaboration. This layer directly interacts with the Service layer. This layer is made up
of the following classes.
3.3.1 Client Manager
This class is responsible for smooth operation of all the services. The user manager
provides helpful information to all the services such as the name of the user and list of
names of all the peers that the user is in collaboration with. Also the client manager is
directly in contact with every service through the base "Service" class. The client
manager forwards the message from all the services to the Packet Filter obj ect. Once the
Packet Filter obj ect splits the message into smaller messages if necessary, the client
manager forwards the messages one level down to the Communication Manager. The
client manager is also responsible for shutting down all the services and the
Communication Manager when the application exits. In short the client manager manages
all the utility classes in the API i.e., the Packet filter, Message Router, all the services,
the Communication Manager and the client identity.
3.3.2 Client Frame
This class acts as a container for all the services. All the services system level and
user level are contained in the Client Frame. This class keeps a record of all the
registered services in the application. The client frame provides the interface to the
application developer to add custom services. The client frame can also be used to
initialize the system-level services that are absolutely required for the application to run
ex. Ping service, identity protection service, etc. Whenever a new service is added to the
client frame, the client frame makes sure that the new service is added to the main menu
of the application. When the user clicks on the main menu of the application and selects a
service, it's the client frame that actually displays the appropriate service on the screen.
Thus this class is also responsible for allowing the user to switch between different
services through the main menu of the application.
3.3.3 Message Router
The instance of this class runs as a separate thread from the main application.
Message Router is managed by the Client Manager. The Client Manager enables routing
at the initialization of the application and disables it when the application terminates. The
Message Router is responsible for routing the messages that it gets from the lower layers
in the API to their destination services, which are one layer up. For every incoming
message the Message Router first checks the header of the message to figure out which
service is the recipient of the message. The Message Router is also responsible for
forwarding packets to the packet filter if the message is marked as a partial message.
3.3.3 Object Rebuilder
The Obj ect Rebuilder runs as a separate thread from the main application. It is
started by the Packet Filter whenever the Packet Filter receives all the parts of a partial
message. The Object Rebuilder uses the partial messages and the sequence number
associated with each message to construct the original message. Once the message is
constructed, it forwards the message to the message router. For every message that is
broken into partial messages, there is one Obj ect Rebuilder. The Obj ect Rebuilder thread
dies as soon as it finishes the construction of the original message.
3.3.4 Packet Filter
The Packet Filter is managed by the Client Manager. The Packet Filter is initialized
when the application starts up. The main j ob of the Packet Filter is to make sure that the
messages that are sent by the service layer are not bigger than the maximum size allowed
by the communication manager who is one layer below. Whenever the service layer
sends a message to the client manager to transmit out into the network, the client manager
first sends the message to the packet filter. The packet filter checks the size of the
message to make sure that it is not bigger than the maximum allowed size. If the packet is
larger than the allowed size, then the packet filter constructs partial messages, where the
payload of each message is a part of the original message. All the partial messages are
marked with a random sequence number which is common to all the partial messages and
a unique multipacket number which will later be used to put the packets in the right order
to reconstruct the original message. Also all the partial messages are marked as "Partial
Messages" so that they are not forwarded to the service layer directly. Once the original
message is fragmented into smaller messages, the packet filter forwards this array of new
smaller messages to the client manager which is then forwarded to the lower layer for
Whenever the message router receives a message/packet that is marked as a
partial message, instead of forwarding the message to the service layer, it will forward the
message to the packet filter. The packet filter at all times maintains a hashtable of partial
messages. Each entry in the hashtable is formed of a pair of sequence number and an
array of messages. Whenever the message router forwards a packet to the packet filter,
the packet filter first gets the sequence number of the packet. Then it will check the
hashtable to see if it already has packets with the same sequence number in the hashtable.
If it finds the sequence number in the hashtable, then it will append the packet in the
array associated with that particular sequence number. If that particular sequence number
is not present in the hashtable, then it will add a new entry for that sequence number. The
array associated with that sequence number will be empty. Now every time the packet
filter adds a partial message to any of the arrays in the hashtable, it will check if the array
is full. If the array if full, then it initializes a new Obj ect Rebuilder and assigns it the full
array. Also at this point it will delete the entry associated with that array from the
3.4 Communication Management Layer
This layer of the API abstracts the details of communication with other
collaborators in the wireless network. The application made using the YCAB.NET CF
API, can be used in an ad-hoc mode where there is no physical infrastructure available to
support connection between peers. Also the same application can be used in an
infrastructure mode where there is a structural wireless network established by using
wireless access points and/or wireless routers. This layer provides a unique interface to
the layers above, so that the services layer or the client management layer does not have
to know which medium (ad-hoc or infrastructure) is used for communication. The only
class that resides on this layer and provides this high level of abstraction to the layers
above is the "Communications Manager" class. This layer directly interacts with the
lowest layer in the API namely the "Data Transfer Layer" and the layer above the current
layer namely the "Client Management Layer". When the application is initialized, the
user is asked to chose the medium of communication as seen in the figure below.
Ad-Hoc or Infrastructure?
Figure 3.10 Network mode selection during startup
If the user selects the Ad-Hoc mode, then the communication is done using the User
Datagram Protocol UDP. If the user selects the infrastructure mode then the
communication is done using the Transmission Control Protocol TCP. Either way all
the classes above this layer never have to know as to what mode is used to exchange
messages. The communications manager manages the two main components that reside
in the "Data Transfer Layer". These components are described in the following section.
3.5 Data Transfer Layer
This layer consist of two main components namely the "Receiver" and the
"Sender". Both of these components are initialized by the communications manager.
Depending on the communication mode the user chooses during the initialization of the
application, the communications manager will initialize the receiver and the sender. If the
mode selected is ad-hoc, then the receiver and sender will be initialized in such a manner
that they will listen and send UDP messages to/from the socket. If the selected mode is
infrastructure, then the communications manager will initialize the receiver and the
sender to listen and send TCP messages to/from the socket.
When the selected mode of communication is infrastructure, then there is a central
server to which all the collaborators have to connect in order to communicate with each
other. There is a server included in the YCAB.NET CF API. The server is implemented
in Java so it can be run from any operating system i.e., Solaris, Linux, Windows, etc.
The following section will give brief description of the server.
3.6 YCab.net CF Server
The server plays an important role in providing the communication level
abstraction to all the layers in the API. All the components of different layers of the API
described above function in the exact same manner when the server is used for
communication and even when communication is done directly in an ad-hoc network
environment. The server acts as message router. The server can be initialized by passing
the port number to be used as an argument. The only requirement for the server to run
properly is a valid public IP address, one open port and the Sun Microsystems's Java
Virtual Machine. To initialize the server, the following command should be used at the
prompt %> java Server x
where x is a valid open port number.
The server has following main components.
3.6.1 Central Storage of Messages
There is a class called "Messages" in the YCab.net CF server. This class acts as a
central storage. All the incoming messages are stored in a queue. The first message to
arrive is the first message to depart from the queue. This allows the proper ordering of
messages. Every time a client sends a message to the server, the server forwards that
message to this central storage. The message is put at the end of the queue. The central
storage also keeps track of currently active number of clients. This storage directly works
with two other components of the server i.e., Message Reader and Message Writer. This
storage facility has an algorithm to make sure that duplicate messages are not sent to the
same client. When a message writer requests a new message, the central storage will
increment a counter. When that counter becomes equal to the number of clients, that
message is permanently deleted from the queue and the temporary counter is again set to
zero. Whenever a new client connects with the main server, the number of clients is
incremented by one. Also whenever a client disconnects from the server, the message
reader or the message writer will notify the central storage, so the number of clients will
be decremented by one.
3.6.2 Main Server
The main server listens for connections on the port number specified as the
command line argument. But before it starts listening, it creates an instance of
"Messages". This obj ect acts as the central storage of messages. Now whenever a client
tries to connect to the server, the server creates a new thread to handle the client, so for
each client, there is a separate server thread. Once the server creates a new thread, that
thread is assigned the current client. This new server thread is also given a reference to
the central storage of messages. The main server again goes back to listening. The call to
the listen method in the main server is blocking, so the server is not using any resources
while it is waiting for connections.
3.6.3 Server Thread
Whenever a new client tries to connect to the YCab.net CF server, the main server
creates an instance of the "Server Thread". Also the main server gives the server thread a
client to handle and the reference to the central storage of messages. Now the server
thread gets the input stream and output stream of the client socket that is used for
communication between the main server and the client. The server thread instantiates two
new obj ects i.e., Message Reader and Message Writer and passes them the input stream
and output stream respectively. The Message Reader and Message Writer both run as
separate threads. The server threads' job is done at this point.
3.6.4 Message Reader
The message reader is responsible for getting all the incoming messages from the
client. Whenever the message reader gets a message from the client, it forwards the
message to the central storage. Once the message is forwarded, the message reader goes
back to reading.
3.6.5 Message Writer
The message writer is responsible for sending all the messages stored in the central
storage to its client. The message writer sleeps until there is a new message to be sent.
When there is new message available in the central storage, it will forward that message
to its client and go back to sleep again.
DEVELOPMENT USINTG YCAB.NET CF
The YCab.net CF API was developed using C# (pronounced C Sharp)
programming language. C# can be written in any text editor. C# does not require any
special Interactive Development Environment (IDE), however the entire YCab.net CF
API was developed using the Microsoft Visual Studio. NET 2003 (VS) IDE because VS
provides a very proactive development environment that supports editing, compiling and
debugging programs written in over 17 different languages. Note here that the
development environment is VS 2003 and not VS 2002. This is because only VS 2003
and newer versions of VS will support development for mobile devices. Some of the
main features of VS 2003 are as follows.
* Visual form designer VS allows developers to design Windows Forms by just
dragging and dropping controls such as buttons, text-boxes, labels etc.
* VS checks for syntactic errors while the developer is coding. In figure 4.1, there is
an extra closing parenthesis at the end. VS will immediately detect it and notify the
developer by showing the red line where there is an error and also a hint as to what
could be the reason for the error.
public void ping()
< Invalid expression term ')'I
// derived from base class "Service"
Figure 4.1 Error detecting feature in Visual Studio.NET 2003
* VS has a very robust built-in debugger, which lets you insert breakpoints, lets you
execute the code line by line and also lets you set a "watch" on variables, that
notifies the developer when the value of a certain variable changes. There are a lot
of advanced debugging options available in VS, but it is beyond the scope of this
thesis to describe them.
*VS has built in support for Smart Device Extensions, which is a Microsoft product
that allows developer of C# and Visual Basic.NET to develop application for
For developing applications using the YCab.net CF API, the developer is not
required to use VS, but it is highly recommended that he/she does because of the ease in
development process. VS facilitates easy and rapid application development.
This section provides a step by step instruction on how to create a simple
application using the YCab.net CF API. The API provides a very intuitive interface for
the developers. The application will connect any number of clients using the TCP/IP or
UJDP protocols, but the developer is not required to have any networking knowledge. The
developer is only required to be familiar with C# programming language and some what
familiar with Visual Studio .NET 2003. Also the developer is required to know the
interface of the YCab.net CF API which is well documented in the API documentation
provided with the YCab.net CF API.
4.1 Design Specifications
This sample application will have a screen with a colored background, and a button
labeled "Next". Also there is a sequence of colors defined in the application. When the
user will click on the "Next" button, the background color of the screen will change to
the next color in the predefined sequence. The next button can be clicked however many
times and by any of the collaborators. At any given time all the collaborators will see the
exact same color on the screens of their mobile devices.
4.2 Loading YCab.net CF
Start up Visual Studio .NET 2003. From the main menu of VS, select the option to
open an existing proj ect. Browse to the directory where YCab.net CF is installed and
select the main proj ect file. If there is no error displayed then, YCab.net CF has
successfully loaded at this point.
4.3 Creating a Custom Service
Now from the proj ect menu, select "Add Class", then name the class
SharedColor as shown in the following figure.
Categories: [emplates;Is a
B B Local Project Items
XML F le Code File Text File
Bltmap File Cursor File Icon File
SA form for Windows Applications
Q pen _1 Cancel H elp
Figure 4.2 Adding a new class to the proj ect
Make sure the icon selected in the Templates panel is that of "Windows Form".
Now VS will display an empty Windows Form. This is where the GUI components will
be added. Now from the toolbox panel drag a "Panel" and drop it on the center of the
form. Also drag and drop a button below the panel on the form. Label the button "Next"
by going to the properties menu. Now the form should look like the following figure.
Figure 4.3 Design view of the SharedColor service
4.4 Setting the Namespace
Like in C and C++, C# also has a special reserved keyword to import additional
classes. In C# that keyword is "using". In C# reference to external namespaces can be
made using the word "using". YCab.net CF is organized by using namespaces. All the
services system level and user level are contained in the ycService namespace. In
order for the SharedColor service to work, it should also belong to the ycService
namespace. In visual studio, the code for a Windows Form can be viewed by pressing the
"F7" function key on the keyboard. A Windows Form in VS has two views, the designer
view as shown in the figure above and the code view. By pressing F7 the code view is
displayed and by pressing Shitf+F7 the design view is displayed. In the code view, set the
namespace to ycService. Also at the top of the document add the ycClient namespace, as
any service in YCab.net CF has to reference this namespace. After all these changes the
top of the code view should look like the following.
yc ,5ervice.5SharedColor I
us ing System. Windows .Forms;
/// Stacanary description for SharedColor.
public class SharedColor : SyJstem.Windows. Forms. Form
Figure 4.4 Setting proper namespaces
4.5 Setting Inheritance
All the services in the YCab.net CF API inherit either from the class Service or
ThreadedService. Those services that are visible and contain GUI components inherit
from the class Service and the ones that run in the background and are not visible inherit
from the class ThreadedService. The SharedColor service is a visible service so it should
extend the class Service. By default a Windows Form inherits from the
System.Windows.Forms.Form class as shown in Eigure above. Now change that to inherit
from class Service as shown in figure below.
publiclc class SharedColor : System.Windows.Forms.Form
public class SharedColor : Servicel
Figure 4.5 Setting proper inheritance
The only problem that arises because of this change is that now VS will not display
the design view of the SharedColor because now SharedColor does not inherit from
System.Windows.Forms.Form class, so whenever a change has to be made to the design
of the form, uncomment the first line in the previous figure and comment the second line.
When done with the changes in the design of the form save the file and let the
SharedColor class inherit from Service again.
4.6 Implemented SharedColor Class
At this point all the necessary setup is done. As specified in the design of
SharedColor, initialize an array of colors as shown below in the constructor.
public class SharedColor : Service
private System.Windows.Forms.Panel panell;
private System.Windows.Forms.Button button;
private Color  colors;
private int colorIndex;
public SharedColor ()
//Required for Windows Form Designer support
//TODO: Add any constructor code after InitializeComponent call
//init the sequence of colors
colors = new Color ;
colors[O] = Color.Blue;
colors = Color. Orange;
colors = Color.Yellow;
colors = Color.Red;
colors = Color.Green;
//init the color-index
colorIndex = O;
Figure 4.6 Constructor of SharedColor class
Also declare an integer to keep track of which color to show next when the user
clicks on the "Next" button.
4.7 Handling User Input
Windows programming is event driven. So until the user interacts with the
SharedColor service using the keyboard or the stylus, the SharedColor service will be
idle. The moment a key is pressed on the mobile device or a stylus is touched on the
screen, an event is generated. If a method is registered with that event, then it will be
called or else SharedColor will ignore the event and again will become idle. As specified
in the design specification of SharedColor, something needs to be done when the user
clicks the "Next" button on the screen. An event handler can be associated with a GUI
component by double-clicking on the control in the design view of SharedColor. When
the "Next" button is double clicked in the design view, the code view is displayed as
shown in figure below.
private void buttonl Click~objct sender, System.Event~rgs e)
Figure 4.7 Adding an event handler
The method button1 Click" is an event handler. This method will be called
whenever the user clicks on the "Next" button on the SharedColor service. VS
automatically registers this event handler with the button when the button is double-
clicked in the design view.
When the user will click on the "Next" button, the color of the screen should be
changed to the next color in sequence, so in this method a message should be sent to all
the collaborators which will change everyone' s screen color to the next color in
sequence. In order to accomplish this, every time the user clicks on the "Next" button, a
message containing the index of the color will be sent out. The "buttonl_Click" method
should me implemented as shown in the following figure.
private void buttonl Click~object sender, System.Event~rgs e)
// convert the integer to bytes
byte  message = BitConverter. GetBytes Ithis. colorIndex) ;
// send the message
// increment the index
// reset the index if needed
if~this.colorIndex == this.colors.Length)
this.colorIndex = O;
Figure 4.8 Implementation of the event handler for SharedColor service
As seen in the previous figure, the method "send" is used to send the message. This
method is inherited from the base class "Service". Also the second parameter of the
method is "Protocol.ALL". The class Protocol is implemented under the namespace
"ycClient", which is included in the SharedColor class at the beginning. Protocol class
contains all the useful constants. The second argument is the recipient of the message, but
as we want all the collaborators to receive this message, Protocol.ALL is used as the
4.8 Processing Incoming Messages
All the classes that inherit from the class "Service" should override a method with
the signature processMessage (byte  msg, string sender). This method will be called by
the API whenever there is a message sent by any of the other collaborators. In
SharedColor the parameter msg, will contains the index of the color to be displayed on
the screen. The processMessage method should be implemented as shown in the
public override void processMessage~byte msg, string sender)
// get the int out of the message
int index = BitConverter.Tolnt32 (msg,0);
// set the screen color
this.panell.BackColor = this.colors[index];
// point to the next color in sequence
this.colorIndex = index+1;
// reset the index if needed
if~this.colorIndex == this.colors.Length)
this.colorIndex = 0;
Figure 4.9 Implementation of processMessage
Now the SharedColor service is completely ready for use. The last thing that needs
to be done is adding SharedColor to the application. Even though, SharedColor service is
implemented under the ycService namespace, it does not automatically become part of
the application. It needs to be added to the Client Frame of the YCab.net CF application.
Under the namespace YCabNetCF, there is a class named YCabNetCF. This class
contains the "Main" method which is the method that gets executed upon application
startup. In this class there is a method names "Start". This is the method that adds all the
user-level services to the client frame. The system level services are automatically added
by the client frame. Add the SharedColor service to the client frame along with other
services. After the SharedColor service is added, the Start method should look like the
public static vold Start (ConnectionInfo info, Form f)
// init the client frame
ClientFrame frame = new ClientFrame~info.ip, info.port, info.userid, info.mode);
// add the text chat service
f rame.addService (new Chat() "Text Chat", true);
// add the white board service
frame.addService Inew WhiteBoard(), "White Board", true);
// add the shared files service
f rame.addService (new SharedFiles() "Shared Files", true);
// add the shared image service
f rame.addService (new ImageViever () "Shared Image", true) ;
// add the audio chat service
frame.addService Inew Audio(), "A~udio chat", true);
// add the shared color service
f rame.addService (new SharedColor() "Shared Color", true);
// start the application
Figure 4.10 Adding the new service to the Client Frame
When adding a service to the client frame, the first parameter is the actual obj ect
that is instantiated from the class, the second argument is the text that appears in the main
menu for that service and the third parameter is the boolean value specifying if the
service should be visible or run in the background.
4.9 Compiling and Deploying
Now the application is ready for compilation. In VS under the Build menu, the
option "Build Solution" will compile the project. There should not be any errors if the
steps described above are strictly followed. Now the application is ready to be deployed
to the Pocket PC device. To deploy the application from the Build menu, the "Deploy
Solution" option will install the application on the Pocket PC under the "Program Files"
Once the application is run, the SharedColor service will be automatically added to
the main menu of the application as shown in the following figure.
Figure 4. 11 SharedColor automatically added to the main menu
Once the Shared Color service is selected, the user can rotate the color of the screen
by clicking next. The first color in the predefined sequence is blue. Now if the user clicks
on "Next" button, the next color in sequence is orange. This scenario is shown in the
following two figures.
Blu sceenris se~rvieRs Help MFdl File Services Help
Figure 4.12 Initial screen of SharedColor (left), SharedColor screen after one vl
CONCLUSION AND FUTURE WORK
YCab.net CF is a descendant of the YCab.net, which in turn is a descendant of
YCab Java. The YCab proj ect in general has improved in terms of its use on mobile
devices. YCab Java was developed for desktops and laptop computers that supported Sun
Microsystems's Java Virtual Machine. Most of the small mobile devices today i.e.,
handheld PCs and Smart phones do not have a Java Virtual Machine, so YCab Java can
not be used on such devices. Then YCab.net was developed which uses Microsoft' s .NET
framework. At the time YCab.net was developed, Microsoft had plans for releasing a
sub-set of the .NET framework for handheld devices. YCab.net laid the foundation for
YCab.net CF which is discussed in this thesis, but it could not be used to develop
applications that would run on handheld devices. YCab.net CF is currently supported on
handheld devices running the Microsoft PocketPC operating system. With few changes in
the GUI and almost no changes in the any other part of the YCab.net CF architecture,
YCab.net CF can be used to create applications for cellular phones running the Microsoft
SmartPhone 2003 operating system. Thus YCab.net CF has fulfilled the long term vision
of creating a true collaboration framework that can be used to create applications that
would run on mobile devices such as handheld PCs and cellular phones.
Improvements in the YCab.net CF API
This section briefly explains the changes that could possible improve the overall
performance of YCab.net CF API. Due to the lack of time, these changes have been made
5.1 YCab.net CF Server
All the previous versions of the YCab proj ect were developed for ad-hoc mobile
collaboration so the collaboration space could be created in ad-hoc network environment
only, where there the internet is not available. Also in ad-hoc mode, the collaborators are
required to be within a radius of certain distance. This is because of the limitation
inherited by the application from the wireless card installed on the mobile device. The
version discussed in this thesis i.e., YCab.net CF has enhanced the framework by
introducing a new feature that allows remote collaboration via the internet. All the
collaborators connect to a central server and the virtual collaboration space is created.
The Java server discussed earlier in this thesis can be improved in terms of performance
and robustness. Also the server could store userid and their passwords and thus an
authentication layer can be added to the current architecture.
Also in the current version of YCab.net CF, all the messages are sent in form of
byte arrays. The arrays contain the header information and then the actual message that is
being sent. It would be difficult, but not impossible to intercept the messages and
reconstruct the information that is being sent. A security layer can be added which would
fit between the communication management layer and the data transfer layer.
5.3 New Services
The true value of YCab.net CF would always increase by adding new built-in
services. A GPS service could be added which would display the true position of all the
collaborators on a map. In this version of YCab.net CF, the audio chat service allows the
collaborators to send and receive voice messages to and from each other. This service can
be improved by allowing the collaborators to send and receive these messages in real-
time as if they are talking to each other using a telephone. A new service could be added
which will allow the collaborators to see each other in real-time using a video camera and
real-time video streaming.
LIST OF REFERENCES
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Framework for Mobile Collaboration." In Proceedings of the ACM~lnternational
Conference on Supporting Group Work, Boulder, Colorado, USA, September
2001, pp. 5-14.
[ 4] Chen, Ing-Ray (2003). M~ultihop Ad Hoc M~essaging Using M~icrosoft.NET
Compact Framnework and Pocket PCs. Available from URL:
Site last visited April 2004.
 Grimes, R. Developing Applications tI ithr Visual Studio .NET. Addison Wesley
Professional, Berkeley, CA, 2002.
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http://www. csharphelp. com/archives/~~rchivel59. html. Site last visited April 2004.
[ 8] Lee, W. D. Decentralized Ad-hoc Groupware API and Framework for M~obile
Collaboration. Thesis for Master of Science, University of Florida, 2000.
 Microsoft Corporation. M~icrosoft C# Language Specifications. Microsoft Press,
Redmond, WA, 2001.
 Microsoft Corporation (1999). Video and Audio Conferencing. Available from
UJRL: http ://www.microsoft.com/netmeeting/. Site last visited April 2004.
[1l] Platt, D. S. Introducing2~icrosoft .NET. Microsoft Press, Redmond, WA, 2001.
 Procopico, Michael. YCAB.NET: Decentralized Collaboration Groupware For
Mobile Devices Using The Microsoft .NET. Thesis for Master of Science,
University of Florida, 2002.
[ 13] Rubin, Erik and Y ates, Ronnie. M~icrosoft .NET Compact Framework Kickstart.
Sams Publishing, Indianapolis, Indiana, 2003.
[ 14] Weisman, C. J. Thze Essential Guide to RF and Wireless, 2nd Edition. Prentice
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 Wigley, S. Wheelwright, R. Burbidge.M\~icrosoft8 .NET Compact Framework
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Mihir P. Patel was born and raised in Guj arat, India. After finishing his high
school, he came to the United States in June 1998. He graduated with Associate of Arts
degree from Palm Beach Community College in 2000. He then attended the University of
Florida and received his Bachelor of Science degree in computer engineering in May
2004. He is a graduate student at the University of Florida in the Department of
Computer and Information Science and Engineering. At present he works part time as a
software developer for the Institute of Food and Agricultural Sciences at the University
of Florida. His interests include mobile computing and game development for mobile
devices. For more information he can be contacted via email at immihir@hotmail. com.