SITL: Fixes, improvements to Airsim multi-vehicle script

1. Kill all running Copter binaries while exiting
2. Set default GCS IP address
3. Fix mcast ip address for different platforms
4. Set variable for number of vehicles

libraries/SITL/examples/Airsim/follow-copter.sh

@@ -1,10 +1,44 @@
 #!/bin/bash
 
+# Example script for multi-vehicle simulation with AirSim
+# see http://ardupilot.org/dev/docs/sitl-with-airsim.html#multi-vehicle-simulation for details
+
+# Usage - From ardupilot root directory, run - libraries/SITL/examples/Airsim/follow-copter.sh $GCS_IP
+# $GCS_IP is the IP address of the system running the GCs, by default is 127.0.0.1
+
+# Kill all SITL binaries when exiting
+trap "killall -9 arducopter" SIGINT SIGTERM EXIT
+
 # assume we start the script from the root directory
 ROOTDIR=$PWD
 COPTER=$ROOTDIR/build/sitl/bin/arducopter
 
-GCS_IP=$1
+# Set GCS_IP address
+if [ -z $1 ]; then
+    GCS_IP="127.0.0.1"
+else
+    GCS_IP=$1
+fi
+
+# Check if Platform is Native Linux, WSL or Cygwin
+# Needed for correct multicast addressing
+unameOut="$(uname -s)"
+
+if [ "$(expr substr $unameOut 1 5)" == "Linux" ]; then
+    # Check for WSL
+    if grep -q Microsoft /proc/version; then
+        MCAST_IP_PORT="127.0.0.1:14550"
+
+    # Native Linux
+    else
+        MCAST_IP_PORT=""                    # Use default IP, port
+    fi
+
+elif [ "$(expr substr $unameOut 1 6)" == "CYGWIN" ]; then
+    MCAST_IP_PORT="0.0.0.0:14550"
+fi
+
+
 
 BASE_DEFAULTS="$ROOTDIR/Tools/autotest/default_params/copter.parm,$ROOTDIR/libraries/SITL/examples/Airsim/quadX.parm"
 
@@ -13,13 +47,16 @@ BASE_DEFAULTS="$ROOTDIR/Tools/autotest/default_params/copter.parm,$ROOTDIR/libra
 	./waf copter
 }
 
-# start up main rover in the current directory
-$COPTER --model airsim-copter --uartA udpclient:$GCS_IP --uartC mcast: --defaults $BASE_DEFAULTS &
+# start up main copter in the current directory
+$COPTER --model airsim-copter --uartA udpclient:$GCS_IP --uartC mcast:$MCAST_IP_PORT --defaults $BASE_DEFAULTS &
+
+# Set number of extra copters to be simulated, change this for increasing the count
+NCOPTERS="1"
+
 
 # now start another copter to follow the first, using
 # a separate directory to keep the eeprom.bin and logs separate
-# for increasing the number of copters, change the number in seq
-for i in $(seq 1); do
+for i in $(seq $NCOPTERS); do
     echo "Starting copter $i"
     mkdir -p copter$i
 
@@ -36,7 +73,7 @@ FOLL_SYSID $FOLL_SYSID
 FOLL_DIST_MAX 1000
 EOF
     pushd copter$i
-    $COPTER --model airsim-copter --uartA tcp:0 --uartC mcast: --instance $i --defaults $BASE_DEFAULTS,follow.parm &
+    $COPTER --model airsim-copter --uartA tcp:0 --uartC mcast:$MCAST_IP_PORT --instance $i --defaults $BASE_DEFAULTS,follow.parm &
     popd
 done
 wait