Simple TCP Netty/Java Server Chat based on a test for the Server Programmer position.

I leave here the specification:

We are building a simple TCP chat server using Netty (https://netty.io/). Only the server implementation is required. Utilities like telnet or nc ( netcat ) shall be used for connecting to the server, perform commands and send messages.

There’s no need for authentication: once a user connects, a random nickname is assigned.

Nicknames are unique, and are released after disconnection.

Users can also join rooms, which are created ad hoc, and once in a room they are able to send and receive messages.

Upon first connection the server replies with a welcome message :)

$ nc localhost 5222

Hello Spiderman

Command /nick <new name> shall be used to change connected user nickname. If a name is already being used, an appropriate error message should be displayed. For instance:

$ nc localhost 5222

Hello Spiderman

$ /nick Batman

Hello Batman

Command /list would output all current room names in the server. For example:

$ nc localhost 5222

Hello Spiderman

$ /list

Superheroes Room

Wannabe Superheroes Room

Marvel

DC

Command /join <room name> is used to join an already existing room, or create one as needed.

• The room should reply with a welcome message, telling how many users are connected in that moment.
• When joining, a user receives the historic of last 5 previous messages, in order.
• Rooms are automatically destroyed when the last connected user leaves.

$ nc localhost 5222

Hello Spiderman

/join superheroes room

Welcome to Superheroes Room, there are 3 users connected.

Batman: I think I’m stronger than Spiderman

Superman: yes, I think so...

Once a user has joined a room, she can freely type to send messages to the users in the chat room, and will receive what others send.

To avoid spam, there is a message rate limit of max 30 messages per minute. Messages that exceed the ratio should be automatically dropped.

Command /exit will disconnect the player from the server. Upon disconnection, the server shall broadcast an information message to other members of the same chat room.

• High concurrency is expected.
• All data is stored in memory, no persistence to database needed.
• Only Java 8, Netty 4 and unit testing libraries are allowed.

With the first connection every one enter into an initial room, a kind of "General Room" channel to bring it closer to what would be the actual operation of an application of this type. This channel, unlike others, will not be deleted when it has 0 users.

All user names created by the / nick command will be limited to 20 characters and with lowercase characters.

All room names created by the / join command will be limited to 20 characters and with lowercase characters.

The / list command shows the list of channels and a (*) next to the name of the channel in which you are at that moment.

• The project code is an exported eclipse project.
• Import the project to eclipse and execute a maven update on the project once imported into the package/project explorer.
• To execute it, the ChatServer.java class must be started (Run/Debug). Once this is done, we can connect using telnet, for example: "$ telnet localhost 8080".