Description
1 Overview
The objective of this assignment is to refresh your memory with the network
programming experience you gained in CSCE 313. To accomplish this, you
will build a Chat Rooms Service.
The system can have several Chat rooms, and clients join chat rooms by
issuing JOIN commands. Clients can also create and delete chat rooms
remotely by issuing CREATE and DELETE commands. All communication
between chat rooms and chat clients will use the network sockets that you
learned in CSCE 313.
1.1 Chat Room Server
The program implementing the Chat Room Server (call it crsd) would
do the following steps in a loop, in any order:
• Listen on a well-known port to accept CREATE, DELETE, or JOIN requests from Chat clients.
• For a CREATE request, check whether the given chat room exists already. If not, create a new master socket (make sure the port number is not usedr) Create an entry for the new chat room in the local
database, and store the name and the port number of the new chat
room. Inform the client about the result of the command.
• For a JOIN request, check whether the chat room exists. If it does,
return the port number of the master socket of that chat room and
the current number members in the chat room. The client will then
connect to the chat room through that port.
Page 1
CSCE 438/438H Spring 2022 Machine Problem 1
• For a DELETE request, check whether the given chat room exists. If
it does, send a warning message (e.g., chat room being deleted,
shutting down connection…) to all connected clients before terminating their connections, closing the master socket, and deleting the
entry. Inform the client about the result.
• Incoming chat messages are handled on slave sockets that are derived
from the chat-room specific master socket. Whenever a chat message
comes in, forward that message to all clients that are part of the chat
room.
• Clients leave the chat room by (unceremoniously) terminating the connection to the server. It is up to the server to handle this and manage
the chat room membership accordingly.
The chat room server is invoked as below:
$crsd
1.2 Chat Room Client
The program implementing the Chat Room Client (call it crc) issues
requests to and exchanges messages with the chat room server.
The client program is invoked as below:
$crc
messages to the currently joined chat room.
The chat room client creates, deletes, and joins chat rooms in the following
way:
• To create a chat room, connect to the well-known port of the chat
server, and send a CREATE
close the connection.
Page 2
CSCE 438/438H Spring 2022 Machine Problem 1
• To delete a chat room, connect to the well-known port of the chat
server, and send a DELETE
close the connection.
• To join a chat room, connect to the well-known port of the chat server,
and send a JOIN
number of the chat room and the current number of members. Display
the information.
• If the JOIN operation was successful, connect to the port returned by
the server, and begin exchanging messages.
• Leave the chat room by terminating the connection.
Note: There is a little complication, as the client program has to read input
both from the command line and from the connection to the chat room. You
have to find a solution to handle this. (One way is to use separate threads
to handle the two input sources, or you can simply use select() to handle
them in a single-thread solution.)
2 What to Hand In
The running system will consist of the chat room server (crsd) and the chat
room client (crc).
As platform, you should be using the programming environment described
below and develop the program in C/C++.
2.1 Design
Before you start hacking away, write down a design document. The result should be a system level design document, which you hand in (on
canvas) along with the source code (in github) – more about submissions
on canvas/github below. Do not get carried away with it, but make sure
it convinces the reader that you know how to attack the problem. List
and describe the components of the system: Chat Client Program, Chat
Room Server Program, and their interaction. In particular, describe how
Page 3
CSCE 438/438H Spring 2022 Machine Problem 1
you implement the server program (iterative, multi-threaded using thread,
multi-threaded using processes, multi-threaded using select(), others.)
2.2 Source code
Your source code, comprising of a Makefile, a file crsd.c, a file crc.c and
any auxiliary files (for example, socket handling) MUST be checked in the
public Github repository here (please note, NOT TAMU Github), using your
Github account and with the project name MP1. Please provide the TA
your Github account name so he can checkout your submission.
The code should be easy to read (read: well-commented!). The instructor
reserves the right to deduct points for code that he/she considers undecipherable.
The design document mentioned above must be submitted through
canvas.
3 Programming Environment
For all Machine Problems in this class you will use a free AWS Cloud 9
environment. Using an environment like this will significantly reduce the
likelihood of environment-related errors for your submissions (when compared to the environment we will be using to test your code).
To setup an AWS Cloud 9 environment, please follow the steps below:
1. Go to aws.amazon.com/cloud9/
2. Click on Sign In to Console button on the top right corner
3. For those without an account please go ahead and click the Create
a new AWS account button towards the bottom, while others can
proceed to login with their credentials
• It is advisable to use university email addresses (tamu.edu) domain to create an account here.
Page 4
CSCE 438/438H Spring 2022 Machine Problem 1
• All accounts created will have free services for upto one year since
the time of initiation of the service
• For more information regarding AWS Free Tier
4. On the search bar up top, proceed to enter Cloud9 and click the
relevant option from the auto populated dropdown.
5. You can go on and click on the orange button titled Create Environment on the right hand side of the screen.
6. Please feel free to name the environment as per your liking and the
click on the Next Step button.
7. In the Configure Settings (the screen that appears after hitting the
Next Step button in the prior step) you can leave the settings as is.
But you can confirm them to ensure that your service usage or request
falls under free tier constraints :
• Environment type : Create a new EC2 instance for environment
(direct access)
• Instance type : t2.micro (1 GiB RAM + 1 vCPU)
• Platform : Amazon Linux 2
• Cost-saving setting : After 30 minutes (default)
8. Once you have confirmed the settings in the above mentioned point,
proceed to click Next Step button, this leads to the review page that
shows all the chosen options. After you review them, you can hit the
Create Environment button
9. Your AWS Cloud 9 environment is created and ready to be used
10. gcc is already setup and ready to be used here
4 Programming Guide
This is a quick guide on how to start your MP1 with a given skeleton code
of a client program. The objective of the skeleton is to let students focus
on socket programming, and also to evaluate your MP fairly by having the
same skeleton. The skeleton has been implemented with almost everything
except the socket programming code.
Page 5
CSCE 438/438H Spring 2022 Machine Problem 1
Please follow the steps below:
• Study the skeleton code provided:
crc.c There is a main function that already has been implemented.
You don’t have to modify the main, but you need to understand what
main function does so that you fill your own code in the skeleton. Also,
there are three functions that have not been implemented yet. Your
job is implementing these three functions.
Interface.h It contains functions that main function uses and Reply
(user defined structure) that you will use in a process command()
function. You don’t have to modify this file.
• Implement three functions:
int connect_to(const char *host, const int port);
struct Reply process_command(const int sockfd, char* command);
void process_chatmode(const char* host, const int port);
There are descriptions of these functions in the skeleton. Please read
the description carefully and follow the suggestions.
• Do not print anything on the screen. The skeleton does print everything on screen for you to interact with a user. What you need to
do is use the get message() function to get a message from a user
during chatting and display message() function to print messages
from other members in a chat room. You can print some debugging
information during the development phase, but you must erase them
when you submit your MP.
• Test your program with the given test cases. There are five test cases
that cover most scenarios. You can see test cases and their results
in the provided excel file. Before test each test cases, restart your
server/client program to have the same output with the given output
in the excel file. Evaluation will be done with different test cases.
Page 6
