ft_irc

An IRC server implementation in C++98, compatible with both Linux (epoll) and macOS (poll).
It supports multiple clients, authentication, nick/user registration, channel management, private messaging, and channel operator commands. Written in a group together with https://github.com/michaela811 and https://github.com/denizcaglarcingoz.

Project is compliant with the subject requirements for 42school ft_irc and with IRC Protocol 1993

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Features

• Non-blocking event loop:
  • Linux → uses epoll
  • macOS → uses poll
• Authentication with PASS, NICK, USER
• Channel system with:
  • JOIN
  • PRIVMSG (private or channel messages)
  • INVITE
  • KICK
  • TOPIC
  • MODE (+i, +t, +k, +o, +l)
• Proper numeric replies for protocol compliance
• Handles edge cases (buffer limits, malformed input, rapid connects, etc.)

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Build

make

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Run

./ircserv <port> <password>

# Example:
./ircserv 6667 mypass

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Event loop differences

• poll (macOS):
  • Scans the full file descriptor set each time.
  • Complexity: O(n) per call.
• epoll (Linux):
  • Kernel stores the set of watched FDs and only reports the ready ones.
  • Amortized complexity: O(ready).
  • Much more scalable for many clients.

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Testing

With HexChat (reference client)

Download: HexChat

1. Start server:

   ./ircserv 6667 mypass

2. In HexChat → Network List → Add a network:
   • Server: 127.0.0.1/6667
   • Password: mypass
   • TLS: disabled
   • Choose a nickname and username
3. Connect and test:

   /join #chan
   /topic #chan :Hello World
   /msg #chan hi all
   /invite othernick #chan
   /kick #chan othernick :bye
   

With nc (netcat)

Terminal A

nc -C 127.0.0.1 6667
PASS mypass
NICK alice
USER alice 0 * :Alice
JOIN #chan

Terminal B

nc -C 127.0.0.1 6667
PASS mypass
NICK bob
USER bob 0 * :Bob
JOIN #chan
PRIVMSG #chan :hello!

Partial packet test (Ctrl+D style)

{ printf 'com'; sleep 1; printf 'man'; sleep 1; printf 'd\r\n'; } | nc -C 127.0.0.1 6667

This simulates sending fragmented input (com + man + d\n). Or while running nc when you have at least one character in your command line just press Ctrl+D whenever you want.

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Job control with nc

Control that the server is still running when one of the clients is suspended. In previously created 'alice' and 'bob':

• on the terminal of bob press Ctrl+Z
• send PRIVMSG from alice to bob
• type fg in bob's terminal to bring him to foreground
• all messages sent by alice should arrive to bob

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Automated tests

From repo root:

./run_all_edge_tests.sh

Or run individually:

./test_buffer_limits.sh
./test_malformed.sh
./test_protocol_violations.sh
./test_rapid_connections.sh
./test_special_chars.sh

These scripts send crafted input via nc to test edge cases.

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Credits

• Authors: grignetta, https://github.com/michaela811 and https://github.com/denizcaglarcingoz