IRC

Internet Relay Chat

IRC Client Comparison

Feature	HexChat	Irssi	WeeChat
Interface Type	Graphical (GUI)	Command-line (CLI)	Command-line (CLI)
Ease of Use	Very high (intuitive GUI)	Moderate (requires CLI skills)	High (user-friendly CLI)
Scripting and Automation	Limited	Extensive (Perl)	Extensive (multiple languages)
Resource Usage	Higher (due to GUI)	Very low	Low
Documentation	Comprehensive	Extensive	Comprehensive and updated
Customization	Moderate	High	Very high (plugins and scripts)
Community Support	Strong	Strong	Strong
Modern Features	Yes (GUI-based)	No	Yes (CLI-based)

IRC Sequence

Login

Usage

Client

We chose WeeChat as client, even though we followed the IRCv3 Protocol that is compatible with most of the IRC current clients.

Add the server in the WeeChat client

/server add my_irc localhost/6667 -password=MYSECUREPASSWORD
/server add my_irc localhost/6667 -password=password

Note

To change the password if needed, we can do that with:

/set irc.server.my_irc.password CORRECTPASSWORD
/save

Connect to the IRC server

/connect my_irc

Network

Ports

Service Name and Transport Protocol Port Number Registry

Note

Internet Assigned Numbers Authority (IANA): Port numbers are assigned in various ways, based on three ranges: System Ports (0-1023), User Ports (1024-49151), and the Dynamic and/or Private Ports (49152-65535);

Category	Port Range
Well-Known / System	0 - 1023
Registered / User	1024 - 49151
Dynamic / Private	49152-65535

Development

Libraries

#include <iostream>         // For standard I/O functions
#include <sys/types.h>      // For data types used in system calls
#include <sys/socket.h>     // For socket, setsockopt, bind, connect, listen, accept, send, recv
#include <netinet/in.h>     // For sockaddr_in, htons, htonl, ntohs, ntohl
#include <arpa/inet.h>      // For inet_addr, inet_ntoa
#include <netdb.h>          // For getprotobyname, gethostbyname, getaddrinfo, freeaddrinfo
#include <unistd.h>         // For close, lseek, fstat
#include <fcntl.h>          // For fcntl
#include <csignal>          // For signal, sigaction
#include <sys/select.h>     // For select
#include <cstring>          // For memset, memcpy
#include <cstdio>           // For standard I/O functions
#include <cstdlib>          // For general utilities like exit()

Capabilities

Client Message	Description	Server Response	Example Server Response
CAP LS 302	Requests list of server capabilities (IRCv3.2)	List the server capabilities	CAP * LS :multi-prefix sasl
CAP LS	Requests list of server capabilities	List the server capabilities	CAP * LS :multi-prefix sasl
CAP LIST	Requests list of currently enabled capabilities	List the currently enabled capabilities	CAP * LIST :multi-prefix
CAP REQ :<capability>	Requests to enable specific capabilities	Acknowledge or deny the capability request	CAP * ACK :multi-prefix (if accepted)
			CAP * NAK :multi-prefix (if rejected)
CAP END	Ends capability negotiation	No response needed	N/A
CAP ABORT	Aborts the capability negotiation	No response needed	N/A
CAP CLEAR	Requests to disable all enabled capabilities	Acknowledge the request	CAP * ACK :
CAP NEW :<capability>	Informs the client of new capabilities after registration	List the new capabilities	CAP * NEW :extended-join
CAP DEL :<capability>	Informs the client of removed capabilities after registration	List the removed capabilities	CAP * DEL :extended-join

Example Server Responses

1. CAP LS 302 or CAP LS:

   CAP * LS :multi-prefix sasl
   

2. CAP LIST:

   CAP * LIST :multi-prefix
   

3. CAP REQ :multi-prefix:

   • If accepted:

     CAP * ACK :multi-prefix
     

   • If rejected:

     CAP * NAK :multi-prefix
     

4. CAP END:

   • No direct response required.

5. CAP ABORT:

   • No direct response required.

6. CAP CLEAR:

   CAP * ACK :
   

7. CAP NEW :extended-join:

   CAP * NEW :extended-join
   

8. CAP DEL :extended-join:

   CAP * DEL :extended-join
   

Summary

• CAP LS 302 and CAP LS: Respond with the list of server capabilities.
• CAP LIST: Respond with the list of currently enabled capabilities.
• CAP REQ :<capability>: Acknowledge or deny the requested capabilities.
• CAP END and CAP ABORT: No response required.
• CAP CLEAR: Acknowledge the request to disable all capabilities.
• CAP NEW :<capability> and CAP DEL :<capability>: Inform the client of new or removed capabilities after registration.

IRCv3 Communication Commands

Command	Parameters	Description	Example	Expected Response
PASS	<password>	Sets a connection password	PASS secretpassword	No response if successful. ERROR message if failed.
CAP	<subcommand> [:<capabilities>]	Requests or lists supported capabilities	CAP REQ :multi-prefix	CAP acknowledgment or error message.
NICK	<nickname>	Sets or changes the user's nickname	NICK newnickname	NICK change confirmation or error if nickname is invalid or in use.
USER	<username> 0 * <realname>	Registers a new user with the server	USER myusername 0 * My Real Name	Welcome messages from the server, including 001 (RPL_WELCOME).
QUIT	[<reason>]	Disconnects from the server, optionally providing a reason	QUIT :Goodbye everyone	No response from the server as the user is disconnected.
JOIN	<channel>{,<channel>} [<key>{,<key>}] Alt Params: 0	Joins one or more channels, optionally with keys Leaves all channels	JOIN #channel1,#channel2 key1,key2 JOIN 0	JOIN confirmation and MODE, TOPIC, and NAMES responses for each channel.
TOPIC	<channel> [<topic>]	Sets or views the topic of a channel	TOPIC #channel :New Topic	TOPIC confirmation or the current topic if no new topic is provided.
KICK	<channel> <user> *( "," <user> ) [<comment>]	Removes one or more users from a channel, optionally with a comment	KICK #channel user1,user2 :Breaking rules	KICK message for each user kicked.
INVITE	<nickname> <channel>	Invites a user to a channel	INVITE friend #channel	INVITE confirmation and notification to the invited user.
MODE	<target> [<modestring> [<mode arguments>...]]	Changes modes for a user or channel	MODE #channel +o username	MODE confirmation message.

• JOIN: Can be used from anywhere in the IRC client to join channels.
• TOPIC: Must be used from within the channel; usually only operators can change it.
• KICK: Must be executed from within the channel; only operators can kick users.
• INVITE: Can be executed from anywhere, specifying the user and channel.
• MODE: Must be used from within the channel; typically requires operator privileges.

MODE Command Options

Option	Description	Example	Expected Response
+i	Sets the channel to invite-only mode	MODE #channel +i	MODE #channel +i confirmation
+t	Only channel operators can set the topic	MODE #channel +t	MODE #channel +t confirmation
+k	Sets a key (password) for the channel	MODE #channel +k secretkey	MODE #channel +k confirmation
+o	Gives operator status to a user	MODE #channel +o username	MODE #channel +o confirmation
+l	Sets a user limit on the channel	MODE #channel +l 50	MODE #channel +l confirmation