public/subjects/net-cat

net-cat

Objectives

This project consists on recreating the NetCat in a Server-Client Architecture that can run in a server mode on a specified port listening for incoming connections, and it can be used in client mode, trying to connect to a specified port and transmitting information to the server.

• NetCat, nc system command, is a command-line utility that reads and writes data across network connections using TCP or UDP. It is used for anything involving TCP, UDP, or UNIX-domain sockets, it is able to open TCP connections, send UDP packages, listen on arbitrary TCP and UDP ports and many more.

• To see more information about NetCat inspect the manual man nc.

Your project must work in a similar way that the original NetCat works, in other words, you must create a group chat. The project must have the following features :

• TCP connection between server and multiple clients (relation of 1 to many).
• A name requirement to the client.
• Control connections quantity.
• Clients must be able to send messages to the chat.
• Do not broadcast EMPTY messages from a client.
• Messages sent, must be identified by the time that was sent and the user name of who sent the message, example : [2020-01-20 15:48:41][client.name]:[client.message]
• If a Client joins the chat, all the previous messages sent to the chat must be uploaded to the new Client.
• If a Client connects to the server, the rest of the Clients must be informed by the server that the Client joined the group.
• If a Client exits the chat, the rest of the Clients must be informed by the server that the Client left.
• All Clients must receive the messages sent by other Clients.
• If a Client leaves the chat, the rest of the Clients must not disconnect.
• If there is no port specified, then set as default the port 8989. Otherwise, program must respond with usage message: [USAGE]: ./TCPChat $port

Instructions

• Your project must be written in Go

• Start TCP server, listen and accept connections

• Your project must have Go-routines

• Your project must have channels or Mutexes

• Maximum 10 connections

• The code must respect the good practices

• It is recommended to have test files for unit testing both the server connection and the client.

• You have to be able to handle the errors from server side and client side

Allowed Packages

• io
• log
• os
• fmt
• net
• sync
• time
• bufio
• errors
• strings
• reflect

Usage

$ go run .
Listening on the port :8989
$ go run . 2525
Listening on the port :2525
$ go run . 2525 localhost
[USAGE]: ./TCPChat $port
$

• You should answer the client with a linux logo and ask for their name, when connection is received

$ nc $IP $port
Welcome to TCP-Chat!
         _nnnn_
        dGGGGMMb
       @p~qp~~qMb
       M|@||@) M|
       @,----.JM|
      JS^\__/  qKL
     dZP        qKRb
    dZP          qKKb
   fZP            SMMb
   HZM            MMMM
   FqM            MMMM
 __| ".        |\dS"qML
 |    `.       | `' \Zq
_)      \.___.,|     .'
\____   )MMMMMP|   .'
     `-'       `--'
[ENTER YOUR NAME]:

• Accept connection with non-empty name

The client :

$ nc $IP $port

Server:

$ go run . 2525
Listening on the port :2525

Client1 (Yenlik):

$ nc localhost 2525
Welcome to TCP-Chat!
         _nnnn_
        dGGGGMMb
       @p~qp~~qMb
       M|@||@) M|
       @,----.JM|
      JS^\__/  qKL
     dZP        qKRb
    dZP          qKKb
   fZP            SMMb
   HZM            MMMM
   FqM            MMMM
 __| ".        |\dS"qML
 |    `.       | `' \Zq
_)      \.___.,|     .'
\____   )MMMMMP|   .'
     `-'       `--'
[ENTER YOUR NAME]: Yenlik
[2020-01-20 16:03:43][Yenlik]:hello
[2020-01-20 16:03:46][Yenlik]:How are you?
[2020-01-20 16:04:10][Yenlik]:
Lee has joined our chat...
[2020-01-20 16:04:15][Yenlik]:
[2020-01-20 16:04:32][Lee]:Hi everyone!
[2020-01-20 16:04:32][Yenlik]:
[2020-01-20 16:04:35][Lee]:How are you?
[2020-01-20 16:04:35][Yenlik]:great, and you?
[2020-01-20 16:04:41][Yenlik]:
[2020-01-20 16:04:44][Lee]:good!
[2020-01-20 16:04:44][Yenlik]:
[2020-01-20 16:04:50][Lee]:alright, see ya!
[2020-01-20 16:04:50][Yenlik]:bye-bye!
[2020-01-20 16:04:57][Yenlik]:
Lee has left our chat...
[2020-01-20 16:04:59][Yenlik]:

Client2 (Lee):

$ nc localhost 2525
Yenliks-MacBook-Air:simpleTCPChat ybokina$ nc localhost 2525
Yenliks-MacBook-Air:simpleTCPChat ybokina$ nc localhost 2525
Welcome to TCP-Chat!
         _nnnn_
        dGGGGMMb
       @p~qp~~qMb
       M|@||@) M|
       @,----.JM|
      JS^\__/  qKL
     dZP        qKRb
    dZP          qKKb
   fZP            SMMb
   HZM            MMMM
   FqM            MMMM
 __| ".        |\dS"qML
 |    `.       | `' \Zq
_)      \.___.,|     .'
\____   )MMMMMP|   .'
     `-'       `--'
[ENTER YOUR NAME]: Lee
[2020-01-20 16:03:43][Yenlik]:hello
[2020-01-20 16:03:46][Yenlik]:How are you?
[2020-01-20 16:04:15][Lee]:Hi everyone!
[2020-01-20 16:04:32][Lee]:How are you?
[2020-01-20 16:04:35][Lee]:
[2020-01-20 16:04:41][Yenlik]:great, and you?
[2020-01-20 16:04:41][Lee]:good!
[2020-01-20 16:04:44][Lee]:alright, see ya!
[2020-01-20 16:04:50][Lee]:
[2020-01-20 16:04:57][Yenlik]:bye-bye!
[2020-01-20 16:04:57][Lee]:^C

Bonus

• Terminal UI (you are allowed to use only this package : https://github.com/jroimartin/gocui).
• Find a way to save all the logs into a file.
• Creating more than 1 group chat.

This project will help you learn about :

• Manipulation of structures.
• Net-Cat
• TCP/UDP
  • TCP/UDP connection
  • TCP/UDP socket
• Go concurrency
  • Channels
  • Goroutines
• Mutexes
• IP and ports