Multicast: client and server

config.py

@@ -0,0 +1,2 @@
+MULTICAST_PORT = 10000
+MULTICAST_IP = '224.0.0.1'

multicast_client.py

@@ -0,0 +1,40 @@
+import socket
+import struct
+import sys
+import config
+
+message = 'SERVER DISCOVERY'
+multicast_group = (config.MULTICAST_IP, config.MULTICAST_PORT)
+
+# Create the datagram socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+
+# Set a timeout so the socket does not block indefinitely when trying
+# to receive data.
+sock.settimeout(0.2)
+
+# Set the time-to-live for messages to 1 so they do not go past the
+# local network segment.
+ttl = struct.pack('b', 1)
+sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl)
+
+try:
+
+    # Send data to the multicast group
+    print('sending "%s"' % message)
+    sent = sock.sendto(bytes(message, encoding='utf-8'), multicast_group)
+
+    # Look for responses from all recipients
+    while True:
+        print('waiting to receive')
+        try:
+            data, server = sock.recvfrom(16)
+        except socket.timeout:
+            print('timed out, no more responses')
+            break
+        else:
+            print('received "%s" from %s' % (data, server))
+
+finally:
+    print('closing socket')
+    sock.close()

multicast_server.py

@@ -0,0 +1,29 @@
+import socket
+import struct
+import sys
+import config
+
+server_address = ('', config.MULTICAST_PORT)
+
+# Create the socket
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+
+# Bind to the server address
+sock.bind(server_address)
+
+# Tell the operating system to add the socket to the multicast group
+# on all interfaces.
+mcast_group = socket.inet_aton(config.MULTICAST_IP)
+mreq = struct.pack('4sL', mcast_group, socket.INADDR_ANY)  # listen on all interfaces `socket.INADDR_ANY`
+sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
+
+# Receive/respond loop
+while True:
+    print('\nwaiting to receive message')
+    data, address = sock.recvfrom(1024)
+
+    print('received %s bytes from %s' % (len(data), address))
+    print(data)
+
+    print('sending acknowledgement to', address)
+    sock.sendto(bytes('ack', encoding='utf-8'), address)