A project developed for the course Computer Networks [NCO-05-02] (2023/24) of the Department of Computer Science at Aristotle University of Thessaloniki (AUTh).
Within the scope of this project, a distributed messaging system was developed using a simple request-reply protocol. Clients send a request to the server, and the server responds with a response, terminating the connection. Specifically, the Sockets technology (Sockets-I/O Streams-Threads) was used.
In this system, different users can create accounts and send messages to each other, with the server handling them. The following components provide this functionality:
- a server program capable of handling multiple requests from clients simultaneously,
- client programs, each capable of sending requests to the server.
The structure of the project is shown in the following UML diagram:
The Client package implements the necessary structures for the user.
Specifically, the Client class is responsible for executing requests to the
server. It accepts the following arguments: ip, port_number, fid, args for
request execution. Additionally, the package includes the RequestHandler
class, which is called by the Client class and is responsible for opening the
connection to the server, sending the request to the server, and finally closing
the connection to the server.
The Common package contains only one class Request that represents requests.
It is used in both the Client and the Server packages for sending and
processing requests, respectively.
The Server package implements the necessary structures required by the server.
Initially, the Server class accepts only one argument, the port_number, which
specifies the port on which it will listen for requests. The ServerHandler
class handles the server's functions, such as user authentication, etc. The
execution of user requests is achieved through the ClientHandler class, which
is called by the ServerHandler and is equipped with methods for displaying a
list of all accounts in the system, sending a message, etc. Additionally, the
package includes the Account, MessageBox, and Message classes, which
represent users, each user's message box, and individual messages, respectively.
- The Server runs indefinitely until the window in which it is running is closed,
- a user's ID consists of 4 random numeric digits,
- a message ID consists of 4 random alphanumeric digits (e.g. gf9U),
- if the required arguments are not provided in a Client execution, nothing is displayed on the screen,
- data syntax is case-sensitive (e.g.
Alex != alex), - it is assumed that numeric values will be provided when needed, and no alphanumeric values will be given,
- user messages cannot contain spaces.