#!/bin/ksh
#This shellscript is udp_receiver.
#Split the standard input into separate files for each port number.
#The names of the files are /tmp/$$.$port
#Then feed each file to the correct program in the directory given as a
#command line argument.
#Sample use: udp_receiver 0_receiverhost

if [[ $# -ne 1 ]]
then
	echo $0: needs one directory name as a command line argument 1>&2
	exit 1
fi

cat > /tmp/$$

while [[ -s /tmp/$$ ]]
do
	#Read the two-byte TCP header.
	length=`chopoff 1 /tmp/$$`
	port=`chopoff 1 /tmp/$$`

	#Demultiplex: write the UDP packet to the file for that port number.
	chopoff $((length - 2)) /tmp/$$ >> /tmp/$$.$port
done

rm /tmp/$$

for prog in $1/*
do
	port=`echo ${prog##*/} | sed 's/\(.\).*/\1/'`
	if [[ -s /tmp/$$.$port ]]
	then
		$prog < /tmp/$$.$port
	fi
done

exit 0