## 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 computer network utility for reading from and writing to 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...
- To see more information about NetCat inspect the manual `man nc` .
Your project must work in a similar way that 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 $port`
This project will help you learn about :
- Manipulation of structures.
- [Net-Cat ](https://linuxize.com/post/netcat-nc-command-with-examples/ )
- [TCP/UDP ](https://www.privateinternetaccess.com/blog/2018/12/tcp-vs-udp-understanding-the-difference/ )
- TCP/UDP connection
- TCP/UDP socket
- [Channels ](https://tour.golang.org/concurrency/2 )
- [Goroutines ](https://tour.golang.org/concurrency/1 )
- Mutexes
- IP and [ports ](https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers )
### Instructions
- Your project must be written in **Go**
- Start TCP server, listen and accept connections
- Your project must have Go-routines
- Your project must have channels or Mutexes
- Maximum 10 connections
- The code must respect the [**good practices** ](https://public.01-edu.org/subjects/good-practices/ )
- It is recommended that the code should present a **test file** for the server connection and the client connection
- You have to be able to handle the errors from server side and client side
### Allowed Packages
- io
- log
- os
- fmt
- net
- sync
- time
- bufio
- errors
- strings
- reflect
### Usage
```console
student$ go build
student$ ./TCPChat
Listening on the port :8989
student$ ./TCPChat 2525
Listening on the port :2525
student$ ./TCPChat 2525 localhost
[USAGE]: ./TCPChat $port
```
- You should answer the client with a linux logo and ask for their name, when connection is received
```console
student$ nc $IP $port
Welcome to TCP-Chat!
_nnnn_
dGGGGMMb
@p ~qp~~qMb
M|@||@) M|
@,----.JM|
JS^\__/ qKL
dZP qKRb
dZP qKKb
fZP SMMb
HZM MMMM
FqM MMMM
__ | ". |\dS"qML
| `. | ` ' \Zq
_) \.___.,| .'
\____ )MMMMMP| .'
`-' ` --'
[ENTER YOUR NAME]:
```
- Accept connection with non-empty name
The client :
```console
student$ nc $IP $port
```
Server:
```console
student$ ./TCPChat 2525
Listening on the port :2525
```
Client1 (Yenlik):
```console
student$ 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):
```console
student$ 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)
- Logging into the file
- Creating more than 1 group chat
