poke

#!/bin/sh
help() { cat <</help
Test an IP or domain name for web service, return false if connection(s) fail
Usage: poke [-av] target[:port] [target[:port] ...]
  -a      Report all failures instead of quitting after first (takes longer)
  -v      Verbose mode.  Reports success or failure (only first failure)
  -2      Run again after 30s and report only target(s) that fail twice
  target  Any IP address or domain name, like 192.168.0.1 or www.google.com
  port    Port to probe (defaults to 80, http)

Part of net-scripts: https://github.com/adamhotep/net-scripts
poke 0.7.20131031.1, Copyright 2005+ by Adam Katz, GPLv2+
/help
}

PORT=80
say=true
ALL() { false; }
filter() { echo "$*"; }
we_have() { type "$@" >/dev/null 2>&1; }

if we_have ncat 	# ncat (comes with nmap v5+) allows wait in ms
  then probe() { ncat --send-only --recv-only -w 334ms $1 $2 >/dev/null 2>&1; }
elif we_have nc 	# netcat; almost every system has this
  then probe() { nc -zw1 $1 $2 >/dev/null 2>&1; }
elif we_have nmap
  then probe() { nmap -p$2 -P0 -sT $1 2>&1 |grep "^$2.*open" >/dev/null; }
elif we_have telnet
  then probe() { echo X |telnet -e X $1 $2 >/dev/null 2>&1; }
else
  echo "ERROR: Missing ncat, nc (netcat), nmap, and even telnet!" >&2; exit 127
fi

while [ -n "$1" ]; do
 case $1 in
  -2* | -a*2* )	shift; say=true;
  		set placeholder -a "$@" --pause "$@" # do it twice!
  		# filter for dups only; anything that fails only once is okay
  		filter() { echo "$*" |sed 's/ /\n/g' |sort |uniq -d; } ;;
  --pause* )	sleep 3 ;;
  -va* | -av*)	shift; set placeholder -v -a "$@" ;;
  -v* | --v* )	say=echo ;;
  -a* | --a* )	ALL() { [ $# -gt 0 ] && date "+%Y%m%d %H:%M:%S $*"; true; } ;;
  -h* | --h* )	help; exit 0 ;;
  -*  | --*  )	echo "poke: invalid argument \`$1'" >&2
 		help|grep ^Usage; exit 2 ;;
  * ) 		P="${1#*:}"
 		[ "$P" = "$1" ] || PORT="$P"
 		TARGET="${1%%:*}"
 		if probe "$TARGET" "$PORT"; then
 		  hits="$hits $TARGET:$PORT"
 		  ALL && $say "poke: successfully connected to $TARGET:$PORT"
 		else
 		  misses="$misses $TARGET:$PORT"
 		  $say "poke: could not connect to port $PORT on $TARGET" 
 		  (! ALL) && exit 1
 		fi ;;
 esac
 shift
done

if [ -z "$hits$misses" ]; then 
  echo "poke: too few arguments" >&2
  echo "Try \`poke --help' for more information." >&2
  exit 2
fi

(! ALL) && $say "poke: successfully connected to each of: $hits"

misses=`filter $misses`
[ -n "$misses" ] && ALL "poke: failed to connect to: $misses" \
  && exit 1 || exit 0