Use port auto-assignment by default

lgl_host_server.py

@@ -28,9 +28,7 @@
 
 Android devices using layers can tunnel their connection using adb reverse
 to forward a Unix domain socket on the device to a TCP socket on the host.
-
-   adb reverse localabstract:lglcomms tcp:63412
-
+This is done automatically by the script.
 '''
 
 import argparse
@@ -60,7 +58,7 @@ def parse_cli() -> argparse.Namespace:
         help='enable the communications unit test helper service')
 
     parser.add_argument(
-        '--android-port', '-A', type=int, default=62142,
+        '--android-port', '-A', type=int, default=0,
         help='enable adb reverse on the specified port for network comms')
 
     parser.add_argument(
@@ -79,20 +77,9 @@ def main() -> int:
     '''
     args = parse_cli()
 
-    # Configure Android adb reverse on the specified port
-    conn = ADBConnect()
-    try:
-        conn.adb(
-            'reverse',
-            'localabstract:lglcomms',
-            f'tcp:{args.android_port}')
-
-    except sp.CalledProcessError:
-        print('ERROR: Could not setup Android network comms')
-        return 1
-
     # Create a server instance
     svr = server.CommsServer(args.android_port)
+    print(f'Server using host port {svr.port}\n')
 
     # Register all the services with it
     print('Registering host services:')
@@ -119,6 +106,18 @@ def main() -> int:
     svr_thread = threading.Thread(target=svr.run, daemon=True)
     svr_thread.start()
 
+    # Configure Android adb reverse on the specified port
+    conn = ADBConnect()
+    try:
+        conn.adb(
+            'reverse',
+            'localabstract:lglcomms',
+            f'tcp:{svr.port}')
+
+    except sp.CalledProcessError:
+        print('ERROR: Could not setup Android network comms')
+        return 1
+
     # Press to exit
     try:
         input('Press any key to exit ...\n\n')

lglpy/comms/server.py

@@ -153,7 +153,7 @@ class CommsServer:
     next message.
 
     Attributes:
-        port: The port the server listens on.
+        port: The port the server listens on, or 0 for auto-assign.
         endpoints: The mapping of addresses to registered microservices.
         sockl: The listener socket, or None if not listening.
         sockd: The client data socket, or None if no client connected.
@@ -167,14 +167,22 @@ def __init__(self, port: int):
         Args:
             port: The local TCP/IP port to listen on.
         '''
-        self.port = port
         self.endpoints = {}  # type: dict[int, Any]
         self.register_endpoint(self)
 
         self.shutdown = False
-        self.sockl = None  # type: Optional[socket.socket]
         self.sockd = None  # type: Optional[socket.socket]
 
+        self.sockl = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.sockl.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+
+        # Set up the listening socket
+        self.sockl.bind(('localhost', port))
+        self.sockl.listen(1)
+
+        # Work out which port was assigned if not user-defined
+        self.port = self.sockl.getsockname()[1]
+
     def register_endpoint(self, endpoint: Any) -> int:
         '''
         Register a new service endpoint with the server.
@@ -220,13 +228,6 @@ def run(self) -> None:
         '''
         Enter server connection handler run loop.
         '''
-        self.sockl = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        self.sockl.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-
-        # Set up the listening socket
-        self.sockl.bind(('localhost', self.port))
-        self.sockl.listen(1)
-
         # Accept a new client connection and assign a data socket
         while not self.shutdown:
             print('Waiting for client connection')
@@ -250,7 +251,6 @@ def run(self) -> None:
                 continue
 
         self.sockl.close()
-        self.sockl = None
 
     def run_client(self) -> None:
         '''