Notes

• select() system call takes linear time with the amount of sockets to monitor and this is limitation of the kernel.
• epoll() and kqueue() are modern replacement which are efficient and offer more events.
• listen() call is non-blocking. OS raises an event on socket when a connection arrives. More Info
• select(), poll(), epoll(), and kqueue() are non-blocking mechanisms.
• overlapped I/O, completion ports are asynchronous mechanisms.

Tools

Following are the list of CLI programs on MacOS for network inspection:

• ifconfig: lists out info about network interfaces
• kextstat: displays kernel extension stats
• networksetup
• odutil
• dns-sd
• /etc/inetd.conf: configure console-only app into networked ones. merged into launchd
• file --mime-type <filename>: displays Content-Type value which can be used for HTTP header data