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122 lines
4.1 KiB
122 lines
4.1 KiB
5 years ago
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## net-cat
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### Objectives
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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 on a specified port and transmitting information to the server.
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- NetCat, `nc` the 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...
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- To see more information about NetCat inspect the manual `man nc`.
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Here is a simple example of connection and transmission between Server-Client by creating a TCP socket between server and client.
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- Open two terminals, one for the server and the other for Client.
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- Use the following commands for the server side :
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```console
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stuednt$ mawk -W interactive '$0="\033[1;32mServer: \033[0m"$0' | nc -l -p <port>
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Client: Hello it's the CLIENT talking
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hello there
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```
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- Use the following commands for the client side :
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```console
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stuednt$ mawk -W interactive '$0="\033[1;32mClient: \033[0m"$0' | nc <host ip> <port>
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Hello it's the CLIENT talking
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Server: Hello there
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```
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- To see the host IP use the command `ifconfig` on the host machine.
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Your project must work in a similar way that NetCat works, in other words you must create a group chat. The project must present :
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- TCP or UDP connection between server and multiple clients (relation of 1 to many), the type of connection must be established by using a flag, just like `nc`, by default it uses TCP connection, if you want to use UDP connection present the flag `-u`.
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- Each Client must have an user name.
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- Clients must be able to send messages to the chat.
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- Messages sent, must be identified by the time that was sent and the user name of who sent the message.
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- If a Client joins the chat, all the messages sent to the chat must be uploaded to the new Client.
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- If a Client connects to the server, the rest of the Clients must be informed by the server that the Client joined the group.
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- If a Client exits the chat, the rest of the Clients must be informed by the server that the Client left.
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- All Clients must receive the messages sent by other Clients.
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- If a Client leaves the chat, the rest of the Clients must not disconnect.
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This project will help you learn about :
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- Manipulation of structures.
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- [Net-Cat](https://linuxize.com/post/netcat-nc-command-with-examples/)
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- [TCP/UDP](https://www.privateinternetaccess.com/blog/2018/12/tcp-vs-udp-understanding-the-difference/)
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- TCP/UDP connection
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- TCP/UDP socket
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- [Channels](https://tour.golang.org/concurrency/2)
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- [Goroutines](https://tour.golang.org/concurrency/1)
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- IP and [ports](https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers)
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### Hints
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- Try to find out more about the flags `-u`, `-p` and `-l`.
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### Instructions
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- Your project must be written in **Go**.
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- Your project must use TCP or UDP.
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- The code must respect the [**good practices**](https://public.01-edu.org/subjects/good-practices.en).
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- It is recommended that the code should present a **test file** for the server connection and the client connection.
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- You have to be able to handle the errors from server side and client side.
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### Usage
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Here is a simple example of a group chat :
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- Server side :
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```console
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student$ ./net-cat -p 8080
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listening on port 8080....
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```
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- Two Clients running at the same time
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- Client 2 :
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```console
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stuednt$ ./net-cat 192.168.1.123 8080
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wellcome, you are connected
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enter user name : client2
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your name is client2
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client2 joined the chat...
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client1 joined the chat...
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hello
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client2 at 18:12- hello
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client1 at 18:13- hello man
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how are you?
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client2 at 18:15- how are you?
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client1 left the chat...
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```
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- Client 1 :
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```console
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stuednt$ ./net-cat 192.168.1.123 8080
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wellcome, you are connected
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enter user name : client1
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your name is client1
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client2 joined the chat...
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client1 joined the chat...
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client2 at 18:12- hello
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hello man
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client1 at 18:13- hello man
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client2 at 18:15- how are you?
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^C
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```
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