Add try_connect_all to allow initialisation without udp broadcast (#1171)

- Try all valid combinations of protocol/transport/device class and attempt to connect. 
- Add cli command `discover config` to return the connection options after connecting via `try_connect_all`.
- The cli command does not return the actual device for processing as this is not a recommended way to regularly connect to devices.

kasa/cli/discover.py

@@ -17,7 +17,7 @@ from kasa import (
 )
 from kasa.discover import DiscoveryResult
 
-from .common import echo
+from .common import echo, error
 
 
 @click.group(invoke_without_command=True)
@@ -145,6 +145,41 @@ async def _discover(ctx, print_discovered, print_unsupported, *, do_echo=True):
     return discovered_devices
 
 
+@discover.command()
+@click.pass_context
+async def config(ctx):
+    """Bypass udp discovery and try to show connection config for a device.
+
+    Bypasses udp discovery and shows the parameters required to connect
+    directly to the device.
+    """
+    params = ctx.parent.parent.params
+    username = params["username"]
+    password = params["password"]
+    timeout = params["timeout"]
+    host = params["host"]
+    port = params["port"]
+
+    if not host:
+        error("--host option must be supplied to discover config")
+
+    credentials = Credentials(username, password) if username and password else None
+
+    dev = await Discover.try_connect_all(
+        host, credentials=credentials, timeout=timeout, port=port
+    )
+    if dev:
+        cparams = dev.config.connection_type
+        echo("Managed to connect, cli options to connect are:")
+        echo(
+            f"--device-family {cparams.device_family.value} "
+            f"--encrypt-type {cparams.encryption_type.value} "
+            f"{'--https' if cparams.https else '--no-https'}"
+        )
+    else:
+        error(f"Unable to connect to {host}")
+
+
 def _echo_dictionary(discovery_info: dict):
     echo("\t[bold]== Discovery information ==[/bold]")
     for key, value in discovery_info.items():

kasa/cli/main.py

@@ -39,6 +39,7 @@ TYPES = [
 ]
 
 ENCRYPT_TYPES = [encrypt_type.value for encrypt_type in DeviceEncryptionType]
+DEFAULT_TARGET = "255.255.255.255"
 
 
 def _legacy_type_to_class(_type):
@@ -115,7 +116,7 @@ def _legacy_type_to_class(_type):
 @click.option(
     "--target",
     envvar="KASA_TARGET",
-    default="255.255.255.255",
+    default=DEFAULT_TARGET,
     required=False,
     show_default=True,
     help="The broadcast address to be used for discovery.",
@@ -256,6 +257,9 @@ async def cli(
         ctx.obj = object()
         return
 
+    if target != DEFAULT_TARGET and host:
+        error("--target is not a valid option for single host discovery")
+
     if experimental:
         from kasa.experimental.enabled import Enabled