Fix/Remote: Improve error handling

docs/MCrecv.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python3
+
+import socket
+import struct
+import binascii
+
+MCAST_GRP = '239.255.1.1'
+MCAST_PORT = 49788
+IS_ALL_GROUPS = True
+
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
+sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+if IS_ALL_GROUPS:
+    # on this port, receives ALL multicast groups
+    sock.bind(('', MCAST_PORT))
+else:
+    # on this port, listen ONLY to MCAST_GRP
+    sock.bind((MCAST_GRP, MCAST_PORT))
+mreq = struct.pack("4sl", socket.inet_aton(MCAST_GRP), socket.INADDR_ANY)
+
+sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
+
+while True:
+    (b, address) = sock.recvfrom(10240)
+    print (address)
+    print (binascii.hexlify(b))

docs/MCsend.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+
+import socket
+
+MCAST_GRP = '239.255.1.1'
+MCAST_PORT = 49788
+
+# regarding socket.IP_MULTICAST_TTL
+# ---------------------------------
+# for all packets sent, after two hops on the network the packet will not 
+# be re-sent/broadcast (see https://www.tldp.org/HOWTO/Multicast-HOWTO-6.html)
+MULTICAST_TTL = 2
+
+sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
+sock.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, MULTICAST_TTL)
+
+# For Python 3, change next line to 'sock.sendto(b"robot", ...' to avoid the
+# "bytes-like object is required" msg (https://stackoverflow.com/a/42612820)
+sock.sendto(b"robot", (MCAST_GRP, MCAST_PORT))