FD_ISSET(int fd, fd_set *set) — Tests if a descriptor is part of a set. 3. The Assignment Blueprint: Mini-Serv / Mini-IRC
: Handle hundreds of concurrent clients on a single thread.
Because the exam environment is restricted (no outside notes or internet), you need to be able to write the socket initialization code from memory. Practice writing the sockaddr_in struct and the bind/listen sequence until it becomes muscle memory. Master the Buffer
: You are usually provided with extract_message and str_join in the provided main.c file during the exam to help manage string buffers. Strategy & Tips
void print_error(char *msg) write(2, msg, strlen(msg)); exit(1); void send_to_all(int sender_fd) for (int i = 0; i <= max_fd; i++) if (FD_ISSET(i, &write_set) && i != sender_fd) send(i, write_buffer, strlen(write_buffer), 0); Use code with caution. Step 3: Main Server Initialization 42 Exam 06
at 42 School involves creating a simple multi-client chat server, typically referred to as mini_serv . The goal is to build a program in C that listens for incoming connections on a specific port and facilitates communication between multiple connected clients. Project Overview
select() (The primary tool for monitoring multiple file descriptors) recv() , send() (Data transmission) write() , close() (Standard I/O operations)
Avoiding "strange errors" often caused by failing to close file descriptors or incorrect FD sets. Tips for Success
When a client joins, the server broadcasts server: client just arrived\n . FD_ISSET(int fd, fd_set *set) — Tests if a
Get the server to accept one connection first. Iterate: Add the broadcast functionality.
Unlike early network projects like ft_irc , Exam 06 condenses the requirements into a single, highly optimized source file. You are given a time limit of 3 to 4 hours to complete it. The grading is binary: your code either passes all automated tests perfectly or receives a zero. Core Technical Requirements
Create a master socket using socket(AF_INET, SOCK_STREAM, 0) .
During the exam, you won't have a GUI. You'll need to use netcat to test your server. Open multiple terminals. Connect to your server using nc localhost [port] . Because the exam environment is restricted (no outside
Broadcast the formatted message to all other active clients by adding it to their respective write buffers or sending it directly when their sockets are ready. Common Pitfalls and How to Avoid Them 1. The "Broken Pipe" (SIGPIPE)
Broadcasting messages from one client to all other connected clients (a basic chat server).
: Assign a specific port and IP address to the socket descriptor.