dobroho_vechora/dobroho_vechora.bash

#!/bin/bash
set -e

mode="${1}"
ip="${2}"
port="${3}"
nick="${4}"

print_usage() {
	echo "${1}"
	echo "${0} <MODE> <IP> <PORT> [NICK]"
	echo "Modes: interactive (intr), send, receive (rec)"
	exit
}
[ -z "${ip}" ]   && print_usage 'No IP given.'
[ -z "${port}" ] && print_usage 'No port given.'
[ -z "${5}" ]    || print_usage 'Too many arguments.'

[ -z "${nick}" ] || nick="<${nick}> "

open_socket() {
	exec 3<> "/dev/tcp/${ip}/${port}"
}

close_socket() {
	exec 3>&-
}

send_message() {
	open_socket
	echo "${1}" >&3
	close_socket
}

get_message() {
	open_socket
	echo "${1}" >&3
	cat <&3 || true
	close_socket
}

case "${mode}" in
	intr)
		;&
	interactive)
		;;
	send)
		open_socket
		text="${nick}$(cat)"
		send_message "0${text}"
		close_socket
		exit
		;;
	rec)
		;&
	receive)
		length="$(get_message 1)"
		open_socket
		echo -n 2 >&3
		head -c "${length}" <&3 
		close_socket
		exit
		;;
	*)
		echo Unknown mode
		exit
esac

while :; do
	read cmd
	case "${cmd}" in
		I)
			b=""
			while :; do
				read c
				[[ "${c}" != "." ]] || break
				if [ -z ${b} ]; then
					b="${c}"
				else
					b="${b}"$'\n'"${c}"
				fi
			done
			send_message 0"${nick}${b}"
			;;
		i)
			read a
			send_message 0"${nick}${a}"
			;;
		p)
			length="$(get_message 1)"
			if [ -z "${length}" ]; then
				echo !;
			else
				open_socket
				echo -n 2 >&3
				head -c "${length}" <&3 | sed -e 's/\x1B/ESC/g' 
				close_socket
			fi
			;;
		q)
			exit
			;;
		*)
			echo ?
			;;
	esac
done