TryHackMe "Looking Glass" - Find the right port with binary search

lookingglass_ssh.txt

#!/bin/zsh
# @author Pichaya Morimoto ([email protected])
# https://tryhackme.com/room/lookingglass
# 10.10.169.23

function ssh_connect {
    ssh [email protected] -p $1 2>/dev/null | grep -q 'Higher' && echo "Higher" && exit 0
    echo "Lower"
}

function binary_search_ssh {
    start=$1
    end=$2
    echo "start ${start}, end ${end}"
    while [ $start -le $end ]; do
        mid=$(( ($start + $end) / 2 ))
        echo "try ${mid}"
        response=$(ssh_connect $mid)
        if [ "$response" == "Higher" ]; then
            echo "Higher"
            end=$(( $mid - 1 ))
        elif [ "$response" == "Lower" ]; then
            echo "Lower"
            start=$(( $mid + 1 ))
        else
            echo "Error: $mid"
            exit 1
        fi
    done
    echo "Could not find SSH service in the specified port range."
}

binary_search_ssh 9000 14000

# $ bash lookingglass.sh
# start 9000, end 14000
# try 11500
# Higher
# try 10249
# Lower
# try 10874
# Higher
# try 10561
# Higher
# try 10405
# Higher
# try 10327
# Lower
# try 10366
# Lower
# try 10385
# Lower
# try 10395
# Higher
# try 10390
# Higher
# try 10387
# Lower
# try 10388
# Lower
# try 10389

# $ ssh [email protected] -p  10389
# You've found the real service.
# Solve the challenge to get access to the box
# Jabberwocky
# 'Mdes mgplmmz, cvs alv lsmtsn aowil
# Fqs ncix hrd rxtbmi bp bwl arul;
# Elw bpmtc pgzt alv uvvordcet,
# Egf bwl qffl vaewz ovxztiql.