#!/bin/ksh
#This shellscript is ip_sender.
#Read input from all the programs in the directories given as command line
#arguments.  The name of each directory begins with a decimal digit giving that
#directory's "IP address".
#
#Split the input into "IP datagrams" of at most 9 bytes each.
#The first three bytes will be decimal digits.
#The first byte is the total length of the datagram (at most 9).
#The second byte is the protocol number (1 for TCP, 2 for UDP).
#The third byte is the "IP address" (read from the directory's name).
#The remaining 6 bytes are a TCP segment.
#
#Sample use: ip_sender 0_senderhost 1_senderhost

if [[ $# -eq 0 ]]
then
	echo $0: needs directory names as command line arguments 1>&2
	exit 1
fi

for host
do
	if [[ ! -d $host ]]
	then
		echo $0: command line argument $host must be a directory 1>&2
		exit 2
	fi

	ip_address=`echo $host | sed 's/\(.\).*/\1/'`

	for prog in $host/*
	do
		if [[ $prog == *_tcp ]]
		then
			protocol=1
			tcp_sender $prog > /tmp/$$
		elif [[ $prog == *_udp ]]
		then
			protocol=2
			udp_sender $prog > /tmp/$$
		else
			echo $0: $prog must end with protocol name 1>&2
			exit 2
		fi

		while [[ -s /tmp/$$ ]]
		do
			chopoff 6 /tmp/$$ > /tmp/$$.data
			length=`wc -c < /tmp/$$.data`
			let length+=3

			#Output the three-byte IP header.
			#The '\c' tells echo not to output a newline.
			echo $length'\c'
			echo $protocol'\c'
			echo $ip_address'\c'

			cat /tmp/$$.data
			rm /tmp/$$.data
		done

		rm /tmp/$$
	done
done

exit 0