Measure TCP throughput between a client and server

tcp_throughput.sh

#!/bin/sh
set -o errexit -o nounset -o noclobber

usage() {
	echo 1>&2 "Intercept TCP communication between a client and server to measure throughput"
	echo 1>&2 "Usage: $0 <MODE> <LISTEN_PORT> <CONNECT_PORT>"
	echo 1>&2 "Where MODE can either be UP or DOWN, for measuring upstream throughput (client to server) or downstream throughput (server to client)"
	exit 1
}

MODE=$1; shift || usage
if [ "$MODE" != "UP" ] && [ "$MODE" != "DOWN" ]; then usage; fi
if [ $# -ne 2 ]; then usage; fi

if [ "$1" = "--connect" ]; then
	shift;
	CONNECT_PORT=$1; shift
	if [ "$MODE" = "UP" ]; then
		pv -brt | socat - TCP:localhost:"$CONNECT_PORT"
	else
		socat TCP:localhost:"$CONNECT_PORT" - | pv -brt
	fi
else
	LISTEN_PORT=$1; shift
	CONNECT_PORT=$1; shift
	echo "Listening for connections on port $LISTEN_PORT, forwarding to port $CONNECT_PORT"
	socat TCP-LISTEN:"$LISTEN_PORT" SYSTEM:"sh $0 $MODE --connect $CONNECT_PORT"
fi