socat-broker.sh

   1 #! /usr/bin/env bash
   2 # Copyright Gerhard Rieger and contributors (see file CHANGES)
   3 # Published under the GNU General Public License V.2, see file COPYING
   4
   5 # Shell script to perform group communications, sometimes called brokering.
   6 # It starts a Socat instance that forks a child process for each
   7 # connected client; the clients communicate via IPv4 broadcast
   8
   9 # Examples:
  10
  11 #   socat-broker.sh TCP-L:1234
  12 # Now connect with an arbitrary number of clients like TCP:<server>:1234
  13
  14 #   socat-broker.sh SSL-L:1234,cert=server.pem,cafile=clients.crt
  15 # Now connect with an arbitrary number of clients like SSL:<server>:1234,cafile=server.cert=clients.pem
  16
  17 ECHO="echo -e"
  18
  19 usage () {
  20     $ECHO "Usage: $0 <options> <listener>"
  21     $ECHO "     <listener> is a passive address like TCP4-L or SSL-L"
  22     $ECHO "     <options>:"
  23     $ECHO "             -d*  -S  -t <timeout>  -T <timeout>     are passed to socat"
  24     $ECHO "             -V      prints the socat command before starting it"
  25     $ECHO "For example:"
  26     $ECHO "     $0 \\"
  27     $ECHO "             TCP4-L:1234"
  28     $ECHO "Then connect with clients to port 1234"
  29     $ECHO "Data sent by any client is forwarded to all other clients"
  30 }
  31
  32 VERBOSE= QUIET= OPTS=
  33 while [ "$1" ]; do
  34     case "X$1" in
  35         X-h) usage; exit ;;
  36         X-V) VERBOSE=1 ;;
  37         X-q) QUIET=1; OPTS="-d0" ;;
  38         X-d*|X-l?*) OPTS="$OPTS $1" ;;
  39         X-b|X-S|X-t|X-T|X-l) OPT=$1; shift; OPTS="$OPTS $OPT $1" ;;
  40         X-) break ;;
  41         X-*) echo "Unknown option \"$1\"" >&2
  42              usage >&2
  43              exit 1 ;;
  44         *) break ;;
  45     esac
  46     shift
  47 done
  48
  49 LISTENER="$1"
  50
  51 if [ -z "$LISTENER" ]; then
  52     echo "$0: Missing parameter" >&2
  53     usage >&2
  54     exit 1
  55 fi
  56
  57 shopt -s nocasematch
  58 if ! [[ "$LISTENER" =~ .*,fork ]] || [[ "$LISTENER" =~ .*,fork, ]]; then
  59     LISTENER="$LISTENER,fork"
  60 fi
  61
  62 case "$0" in
  63     */*) SOCAT=${0%/*}/socat ;;
  64     *) SOCAT=socat ;;
  65 esac
  66
  67 PORT=$($SOCAT -d -d -T 0.000001 UDP4-RECV:0 /dev/null 2>&1 |grep bound |sed 's/.*:\([1-9][0-9]*\)$/\1/')
  68 if [ -z "$PORT" ]; then
  69     echo "$0: Failed to determine free UDP port" >&2
  70     exit 1
  71 fi
  72
  73 BCADDR=127.255.255.255
  74
  75 if [ "$VERBOSE" ]; then
  76     echo -e "$SOCAT -lp socat-broker $OPTS \\
  77         $LISTENER \
  78         UDP4-DATAGRAM:$BCADDR:$PORT,bind=:$PORT,so-broadcast,so-reuseaddr"
  79 fi
  80 $SOCAT -lp socat-broker $OPTS \
  81     "$LISTENER" \
  82     "UDP4-DATAGRAM:$BCADDR:$PORT,bind=:$PORT,so-broadcast,so-reuseaddr"
  83