CS 4390 Project

The group project for CS 4390 (Computer Networks) @ UTD. The Goal is to create a Server/Client chat utilizing UDP and TCP sockets.

This project was written using Intellij IDEA 2020.2.3 (Community Edition), using OpenJDK 14.

Execution

Execution of the code is fairly simple because we went ahead and bundled the program into an executable .jar file. Since this code has two parts, here are two different sets of instructions:

... the Server

This should be run first. Open a terminal window and navigate to the root directory of the project: cs-4390-project/. Then type in the following commands:

~/cs-4390-project~$ cd runnables
~/cs-4390-project/runnables~$ cd server
~/cs-4390-project/runnables/server~$ java -jar server.jar

And now your server should be running. It won't immediately print anything, but if you just hit the ENTER key, you'll see a debug printout. Leave this terminal window open as we open the client.

... and the Client

Open another terminal window and navigate to the root directory of the project: cs-4390-project/. Then type in the following commands

~/cs-4390-project~$ cd runnables
~/cs-4390-project/runnables~$ cd client
~/cs-4390-project/runnables/client~$ java -jar client.jar

You can do this however many times you want to create several instances of the client. Make sure the server is open while you use the client

Client-ID/Password Combinations

Here is a table of the client-id/password combinations of our subscribers. They are here for you to use to login.

Client ID	Password
austin-li	`yo123`
joseph-norman	`toe123`
josh-guzman	`bro123`
kevin-salinda	`moe123`
user1	`pass`
user2	`pass`
user3	`pass`
user4	`pass`
user5	`pass`
user6	`pass`
user7	`pass`
user8	`pass`
user9	`pass`
user10	`pass`

How we are formatting Packet Data

Because this program requires two different programs to talk to each other via UDP/TCP, this README will document the types of packets that will be sent between the server and the client.

In an effort to standardize the formatting of these packets, we will use JSON, a system that allows an array of <key, value> pairs to be formatted into a string, then converted back. The specific details of this will be documented in server/README.md and client/README.md, but the important part is that the strings can be parsed into byte[] streams which can be sent using Java's TCP/UDP libraries. For more information on the JSON format, read here.

Packet Documentation

The following is a listing of all of the different packets we could possible send. Each packet has an identifier that is used to identify what the client or the server should do with it. This identifier is called the receiver and will look like this in the JSON:

{
    "receiver": "HELLO",
    ...
}

When the server receives this packet, it knows that it is the Hello Packet and should look for a CLIENT-ID-A

Hello Packet

The initial packet sent from the Client to the Server via UDP.

Key	Type	Example Value	Description
`CLIENT-ID-A`	String	`joseph-norman-dev`	The ID of the client that is connecting to the server

Example Packet:

{
	"receiver": "HELLO",
	"CLIENT-ID-A": "joseph-norman"
}

Challenge Packet

The packet sent via UDP from server to client that challenges the client to authenticate itself.

Key	Type	Example Value	Description
`RAND`	String	`1938182376`	The random number that the client will use to authenticate itself using the MD5 algorithm

Example Packet:

{
	"receiver": "CHALLENGE",
	"RAND": "1938182376"
}

Response Packet

The packet sent via UDP from client to server that the server uses to respond to the challenge provided. The value of RES is dictated by the formula:

String K_A = "toe123"; //the client's secret key (password) 
String RAND = "1938182376"; //value sent from server in the CHALLENGE Packet 
String RES = MD5(K_A + "," + RAND);

Key	Type	Example Value	Description
`CLIENT-ID`	String	`joseph-norman`	The client id of the Subscriber trying to respond to the challenge
`RES`	String	`C2E67DCE66A2651386F6054FA112E61D`	The hash provided by the MD5 algorithm

Example Packet:

{
	"receiver": "CHALLENGE",
	"CLIENT-ID": "joseph-norman",
	"RES": "961E5D0F404509D43AE2EFFF24489F7D"
}

Auth Success Packet

The packet that is sent via UDP from the server to the client once the client is authenticated (if the proper value of RES is found in the Response Packet). It instructs the client to reconnect to the provided TCP port and to offer its cookie once connected.

Key	Type	Example Value	Description
`PORT`	Integer	`8001`	The TCP port number that the client should connect to
`RAND-COOKIE`	String	`1938182376`	The same string sent by the Challenge packet

Example Packet:

{
	"receiver": "AUTH-SUCCESS",
	"PORT": "8001",
	"RAND-COOKIE": "1938182376"
}

Auth Fail Packet

The packet that is sent via UDP from the server to the client because it failed to authorize. The client will not be instructed to connect to a specific TCP port

Key	Type	Example Value	Description

Example Packet:

{
	"receiver": "AUTH-FAIL"
}

Connect Packet

The packet that is sent via TCP from client to server to authenticate the client and authorize further communication over TCP.

Key	Type	Example Value	Description
`RAND-COOKIE`	String	`1938182376`	A completely random string that the client uses to authenticate itself

Example Packet:

{
	"receiver": "CONNECT",
	"RAND-COOKIE": "1938182376"
}

Connected Packet

The packet that is sent via TCP from the server to the client in order to verify that the client was authorized.

Key	Type	Example Value	Description

Example Packet:

{
	"receiver": "CONNECTED"
}

Chat Request Packet

The packet that is sent via TCP from the client to the server to request a Session be created between the original sender and client B

Key	Type	Example Value	Description
`CLIENT-ID-B`	String	`austin-li`	The Client ID of the other subscriber

Example Packet:

{
	"receiver": "CHAT-REQUEST",
	"CLIENT-ID-B": "austin-li"
}

Chat Started Packet

The packet that is sent via TCP from the server to clients A and B that they are to be conjoined in a chat Session

Key	Type	Example Value	Description
`CLIENT-ID-B`	String	`austin-li`	The Client ID of the other subscriber in the Session
`SESSION-ID`	String	`1`	The Session ID of Session

Example Packet:

{
	"receiver": "CHAT-STARTED",
	"CLIENT-ID-B": "austin-li",
	"SESSION-ID": "1"
}

Chat Message Packet

The packet that is sent via TCP between the clients, relayed by the server. This packet contains the actual chat message and the session id

Key	Type	Example Value	Description
`SESSION-ID`	String	`1`	Session ID number
`CHAT-MESSAGE`	String	`hello`	The chat message sent

Example Packet:

{
	"receiver": "CHAT",
	"SESSION-ID: "1",
	"CHAT-MESSAGE": "hello"
}

History Request Message Packet

The packet that is sent via TCP by the client A to request history of past chat messages with client b.

Key	Type	Example Value	Description
`CLIENT-ID-B`	String	`josh-guzman`	Client-ID of the subscriber that client A is requesting chat history with

Example Packet:

{
	"receiver": "HISTORY_REQ",
	"CLIENT-ID-B": "josh-guzman"		
}

End Notification Message Packet

The packet that is sent via TCP by the server to the client involved in a session that the session has been terminated by another client.

Key	Type	Example Value	Description
`SESSION-ID`	String	`1`	The Session-ID of sendind session

Example Packet:

{
	"receiver": "END-NOTIF",
	"SESSION-ID: "1"		
}

History Reponse Message Packet

The packet that is sent via TCP by the server to the client who requested the history.

Key	Type	Example Value	Description
`CLIENT-ID`	String	`josh-guzman`	Client-ID of the client who sent the chat message
`CHAT-MESSAGE`	String	`hello`	The chat message sent
`SESSION-ID`	String	`1`	The Session-ID of the chat message

Example Packet:

{
	"receiver": "CHAT",
	"CLIENT-ID": "josh-guzman", 
	"CHAT-MESSAGE": "hello",
	"SESSION-ID: "1"		
}

Unreachable Packet

The packet that is sent via TCP from the server to the client to notify client A that client B was unreachable. Either they are not connected or are already in a Session with someone else

Key	Type	Example Value	Description
`CLIENT-ID-B`	String	`austin-li`	The Client ID of the unreachable subscriber

Example Packet:

{
	"receiver": "UNREACHABLE",
	"CLIENT-ID-B": "austin-li"
}

End Request Packet

The packet that is sent via TCP from the client to the server to notify the server that the client wants the current chat session to end. The message is sent whenever a user enters "end chat" during the chat phase

Key	Type	Example Value	Description
`SESSION-ID`	String	``	The session ID of the client's current chat

Example Packet:

{
	"receiver": "END-REQUEST",
	"SESSION-ID": "2"
}

jnorman-us / cs4390-chat-server-client

CS 4390 Project

Execution

... the Server

... and the Client

Client-ID/Password Combinations

How we are formatting Packet Data

Packet Documentation

Hello Packet

Example Packet:

Challenge Packet

Example Packet:

Response Packet

Example Packet:

Auth Success Packet

Example Packet:

Auth Fail Packet

Example Packet:

Connect Packet

Example Packet:

Connected Packet

Example Packet:

Chat Request Packet

Example Packet:

Chat Started Packet

Example Packet:

Chat Message Packet

Example Packet:

History Request Message Packet

Example Packet:

End Notification Message Packet

Example Packet:

History Reponse Message Packet

Example Packet:

Unreachable Packet

Example Packet:

End Request Packet

Example Packet:

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