If no device specified, get the first device found

build/android/adb_reverse_forwarder.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Command line tool for forwarding ports from a device to the host.
 
 Allows an Android device to connect to services running on the host machine,
 i.e., "adb forward" in reverse. Requires |host_forwarder| and |device_forwarder|
 to be built.
 """
 
 import optparse
 import sys
 import time
 
+from pylib import android_commands
 from pylib import constants, forwarder
 from pylib.device import device_utils
 from pylib.utils import run_tests_helper
 
 
 def main(argv):
   parser = optparse.OptionParser(usage='Usage: %prog [options] device_port '
                                  'host_port [device_port_2 host_port_2] ...',
                                  description=__doc__)
   parser.add_option('-v',
@@ skipping 15 matching lines @@
     parser.error('Need even number of port pairs')
     sys.exit(1)
 
   try:
     port_pairs = map(int, args[1:])
     port_pairs = zip(port_pairs[::2], port_pairs[1::2])
   except ValueError:
     parser.error('Bad port number')
     sys.exit(1)
 
-  device = device_utils.DeviceUtils(options.device)
+  devices = android_commands.GetAttachedDevices()
+
+  if options.device:
+    if options.device not in devices:
+      raise Exception('Error: %s not in attached devices %s' % (options.device,
+                      ','.join(devices)))
+    devices = [options.device]
+  else:
+    if not devices:
+      raise Exception('Error: no connected devices')
+    print("No device specified. Defaulting to " + devices[0])
+
+  device = device_utils.DeviceUtils(devices[0])
   constants.SetBuildType(options.build_type)
   try:
     forwarder.Forwarder.Map(port_pairs, device)
     while True:
       time.sleep(60)
   except KeyboardInterrupt:
     sys.exit(0)
   finally:
     forwarder.Forwarder.UnmapAllDevicePorts(device)
 
 if __name__ == '__main__':
   main(sys.argv)