lights: support sending to one or many hosts

lights.py

 #!/usr/bin/env python3
+from collections import defaultdict
 import socket
 import time
 
 UDP_IP = "10.0.0.255"
 UDP_PORT = 1234
 LED_NUM = 42
-TIMEOUT = 1 / 120
+SEND_RATE = 1 / 120
 VERSION = 2
-SEQUENCE = 0
+SEQUENCES = defaultdict(int)
 SOCKET = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
-SOCKET.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 SOCKET.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
 
 
-def send(data):
-    """Send data to the esp listening at UDP_IP:UD_PORT"""
-    global SEQUENCE
-    header = bytes([VERSION, SEQUENCE, 0, 0])
-    SOCKET.sendto(header + data, (UDP_IP, UDP_PORT))
-    SEQUENCE += 1
-    if SEQUENCE == 255:
-        SEQUENCE = 0
-    time.sleep(TIMEOUT)
+def send_broadcast(data):
+    """Send data via broadcast"""
+    send(data, UDP_IP)
+
+
+def send(data, host, send_rate=SEND_RATE):
+    """Send data to the ESP listening at host:UDP_PORT."""
+    global SEQUENCES
+    header = bytes([VERSION, SEQUENCES[host], 0, 0])
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    if host.endswith('255'):
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+    s.sendto(header + data, (host, UDP_PORT))
+    s.close()
+    SEQUENCES[host] += 1
+    if SEQUENCES[host] > 255:
+        SEQUENCES[host] = 0
+    time.sleep(send_rate)
+
+
+def send_to_many(data, hosts):
+    """Send data to a list of ESPs"""
+    for h in hosts:
+        send(data, h, 0)
+    time.sleep(SEND_RATE)
 
 
 def pixel2bytes(pixel):
@@ -50,7 +66,7 @@ def make_stripe_data(pixellist):
 
 if __name__ == '__main__':
     colors = make_stripe_data([0, 255, 255, 0] * 24)
-    SEQUENCE=0
+    SEQUENCE = 0
     send(colors)
-    SEQUENCE=128
+    SEQUENCE = 128
     send(colors)