socket_comms: add helpers for server-port support

Add a argparse helper to add a `--server-port` argument to tools that
need it.
This can be used to specify a different UDP port to allow for multiple
gateway scripts and corresponding connections to run simultaneously.

Signed-off-by: Aeyohan Furtado <aeyohan@embeint.com>

Author: Aeyohan

src/infuse_iot/socket_comms.py

@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 
+import argparse
 import enum
 import json
 import socket
@@ -21,6 +22,25 @@
 def default_multicast_address(port: int = 8751) -> tuple[str, int]:
     return ("224.1.1.1", port)
 
+def server_port_parser(arg_port: str) -> tuple[str, int]:
+    if arg_port is None or arg_port == "":
+        return default_multicast_address()
+    port = int(arg_port)
+    if not (0 < port < 65536):
+        raise argparse.ArgumentError(None, f"Invalid `--server-port`: {port}")
+    if port % 2 == 0:
+        raise argparse.ArgumentError(None, f"`--server-port` must be odd: {port}")
+    return default_multicast_address(port)
+
+def add_server_port_parser(parser: argparse.ArgumentParser, multi_port: bool = False):
+    parser.add_argument(
+        '--server-port',
+        dest='server_sock',
+        default="",
+        type=server_port_parser,
+        nargs= '+' if multi_port else None,
+        help="Alternate port to use for Gateway connections (default 8751)"
+    )
 
 class ClientNotification:
     class Type(enum.IntEnum):