Very basic DNS server written in bash

dns_server.sh

#!/bin/bash
#Based off of http://code.activestate.com/recipes/491264/
if [ "$1" == "startserver" ]; then
    ncat -u -l 5355 -c $(readlink -f $0) -k
    exit
fi
timeout 1s cat /dev/stdin > input
req=$(cat input | xxd -p)

#Functions from http://ubuntuforums.org/showthread.php?t=735140&p=4584216#post4584216
ord() {
  printf '%d' "'$1"
}

chr() {
  printf \\$(printf '%03o' $1)
}

#Modified to be like javascript slice()
slice() {
    begin=$(($2 + 1))
    end=$3
    echo -n $1 | xxd -p -r | cut -b $begin-$end | tr -d '\n'
}


IP='192.168.1.1'

type=$(($(($(ord $(slice $req 2 3)) >> 3)) & 15))

if [ "$type" -eq 0 ]; then
    ID=$(slice $req 0 2 | xxd -p )

    #echo -en "'"$ID"'" | tr -d $'\n'
    ini=12
    lon=$(ord $(slice $req $ini $(($ini + 1))))

    domain=''
    while [ "$lon" -ne 0 ]; do
        domain=${domain}$(slice $req $(($ini + 1)) $(($ini + $lon + 1)))'.'
        #echo $domain
        ini=$(($ini + $lon + 1))
        #echo $ini
        lon=$(ord $(slice $req $ini $(($ini + 1))))
    done

    if [ ! -z "$domain" ]; then
        flags='8180'
        question=$(slice $req 4 6 | xxd -p)
        answer=$(slice $req 4 6 | xxd -p)
        answer2='00000000'
        domainQuestion=$(slice $req 12 | xxd -p)
        domainPointer='c00c'
        resType='0001' #A record
        classType='0001' #IN, internet class
        ttl='0000003c' #1 minute
        resLength='0004' #Data length: > 4 bytes
        resIP=''
        for i in `seq 1 4`; do
            resIP=${resIP}$(chr $(echo $IP | cut -d '.' -f $i) | xxd -p)
        done

        res=${ID}${flags}${question}${answer}${answer2}${domainQuestion}${domainPointer}
        res=${res}${resType}${classType}${ttl}${resLength}${resIP}
        echo -n $res | xxd -p -r

    fi
fi

sleep 1