Added socat-broker.sh for group communications

socat-broker.sh

@@ -0,0 +1,83 @@
+#! /usr/bin/env bash
+# Copyright Gerhard Rieger and contributors (see file CHANGES)
+# Published under the GNU General Public License V.2, see file COPYING
+
+# Shell script to perform group communications, sometimes called brokering.
+# It starts a Socat instance that forks a child process for each
+# connected client; the clients communicate via IPv4 broadcast
+
+# Examples:
+
+#   socat-broker.sh TCP-L:1234
+# Now connect with an arbitrary number of clients like TCP:<server>:1234
+
+#   socat-broker.sh SSL-L:1234,cert=server.pem,cafile=clients.crt
+# Now connect with an arbitrary number of clients like SSL:<server>:1234,cafile=server.cert=clients.pem
+
+ECHO="echo -e"
+
+usage () {
+    $ECHO "Usage: $0 <options> <listener>"
+    $ECHO "	<listener> is a passive address like TCP4-L or SSL-L"
+    $ECHO "	<options>:"
+    $ECHO "		-d*  -S  -t <timeout>  -T <timeout> 	are passed to socat"
+    $ECHO "		-V	prints the socat command before starting it"
+    $ECHO "For example:"
+    $ECHO "	$0 \\"
+    $ECHO "		TCP4-L:1234"
+    $ECHO "Then connect with clients to port 1234"
+    $ECHO "Data sent by any client is forwarded to all other clients"
+}
+
+VERBOSE= QUIET= OPTS=
+while [ "$1" ]; do
+    case "X$1" in
+	X-h) usage; exit ;;
+	X-V) VERBOSE=1 ;;
+	X-q) QUIET=1; OPTS="-d0" ;;
+	X-d*|X-l?*) OPTS="$OPTS $1" ;;
+	X-b|X-S|X-t|X-T|X-l) OPT=$1; shift; OPTS="$OPTS $OPT $1" ;;
+	X-) break ;;
+	X-*) echo "Unknown option \"$1\"" >&2
+	     usage >&2
+	     exit 1 ;;
+	*) break ;;
+    esac
+    shift
+done
+
+LISTENER="$1"
+
+if [ -z "$LISTENER" ]; then
+    echo "$0: Missing parameter" >&2
+    usage >&2
+    exit 1
+fi
+
+shopt -s nocasematch
+if ! [[ "$LISTENER" =~ .*,fork ]] || [[ "$LISTENER" =~ .*,fork, ]]; then
+    LISTENER="$LISTENER,fork"
+fi
+
+case "$0" in
+    */*) SOCAT=${0%/*}/socat ;;
+    *) SOCAT=socat ;;
+esac
+
+PORT=$($SOCAT -d -d -T 0.000001 UDP4-RECV:0 /dev/null 2>&1 |grep bound |sed 's/.*:\([1-9][0-9]*\)$/\1/')
+if [ -z "$PORT" ]; then
+    echo "$0: Failed to determine free UDP port" >&2
+    exit 1
+fi
+
+BCADDR=127.255.255.255
+
+if [ "$VERBOSE" ]; then
+    echo -e "$SOCAT -lp socat-broker $OPTS \\
+	$LISTENER \
+	UDP4-DATAGRAM:$BCADDR:$PORT,bind=:$PORT,so-broadcast,so-reuseaddr"
+fi	
+$SOCAT -lp socat-broker $OPTS \
+    "$LISTENER" \
+    "UDP4-DATAGRAM:$BCADDR:$PORT,bind=:$PORT,so-broadcast,so-reuseaddr"
+