do check if multicast addr before setting multicast options, have exa…

…mples default to unicast UDP case. Fix #3 and is a workaround for #1

examples/microosc_simplesend.py

@@ -12,7 +12,8 @@
 
 import microosc
 
-UDP_HOST = "224.0.0.1"  # multicast UDP
+UDP_HOST = ""  # set to empty string to auto-set unicast UDP
+# UDP_HOST = "224.0.0.1"  # multicast UDP
 UDP_PORT = 5000
 
 ssid = os.getenv("CIRCUITPY_WIFI_SSID")
@@ -43,6 +44,10 @@ def test_low_level():
 
 test_low_level()
 
+if not UDP_HOST:
+    # fall back to non-multicast UDP on my IP addr
+    UDP_HOST = str(wifi.radio.ipv4_address)
+
 osc_client = microosc.OSCClient(socket_pool, "224.0.0.1", 5000)
 
 msg = microosc.OscMsg( "/1/xy1", [0.99, 0.3, ], ("f", "f", ) )  # fmt: skip

examples/microosc_simpletest.py

@@ -13,7 +13,8 @@
 
 import microosc
 
-UDP_HOST = "224.0.0.1"  # multicast UDP
+UDP_HOST = ""  # set to empty string to auto-set unicast UDP
+# UDP_HOST = "224.0.0.1"  # multicast UDP
 UDP_PORT = 5000
 
 ssid = os.getenv("CIRCUITPY_WIFI_SSID")
@@ -39,6 +40,10 @@ def fader_handler(msg):
     "/filter1": fader_handler,
 }
 
+if not UDP_HOST:
+    # fall back to non-multicast UDP on my IP addr
+    UDP_HOST = str(wifi.radio.ipv4_address)
+
 osc_server = microosc.OSCServer(socket_pool, UDP_HOST, UDP_PORT, dispatch_map)
 
 print("MicroOSC server started on ", UDP_HOST, UDP_PORT)

microosc.py

@@ -210,8 +210,8 @@ def _server_start(self, buf_size=128, timeout=0.001, ttl=2):
         self._sock = self._socket_source.socket(
             self._socket_source.AF_INET, self._socket_source.SOCK_DGRAM
         )  # UDP
-        # TODO: check for IP address type? (multicast/unicast)
-        self._sock.setsockopt(IPPROTO_IP, IP_MULTICAST_TTL, ttl)
+        if self.host.startswith("224"):  # multicast
+            self._sock.setsockopt(IPPROTO_IP, IP_MULTICAST_TTL, ttl)
         self._sock.bind((self.host, self.port))
         self._sock.settimeout(timeout)