.

tmcast.py

@@ -9,23 +9,35 @@ from socket import socket, AF_INET, SOCK_DGRAM, IPPROTO_UDP, SOL_SOCKET, \
     SO_REUSEADDR, IPPROTO_IP, IP_ADD_MEMBERSHIP, IP_MULTICAST_TTL, IP_MULTICAST_LOOP,   \
     inet_aton, INADDR_ANY
 
+from golang import b
+from golang import sync, context
+
+
 group4 = '224.1.1.1'
 group6 = 'XXX'
 port   =  5678
 
-# open_rx returns function to receive from group:port.
-def open_rx(group, port):
+# mjoin returns socket prepated to send/receive to/from multicast group:port.
+def mjoin(group, port, ttl=2):
     # XXX autodetect ip4/ip6 based on group addr
     sk = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
     sk.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
     sk.bind((group, port))
 
+    # join group (for rx)
     mreq = struct.pack("4sl", inet_aton(group), INADDR_ANY)
     sk.setsockopt(IPPROTO_IP, IP_ADD_MEMBERSHIP, mreq)
-    def _(): # -> data
-        return sk.recv(4096)
-    return _
 
+    # set ttl and default destination address (for tx)
+    sk.setsockopt(IPPROTO_IP, IP_MULTICAST_TTL, ttl)
+    sk.connect((group, port))
+
+    # receive what we send
+    sk.setsockopt(IPPROTO_IP, IP_MULTICAST_LOOP, 1)
+
+    return sk
+
+"""
 # open_tx returns function to send to group:port.
 def open_tx(group, port, ttl=2):
     sk = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
@@ -34,37 +46,41 @@ def open_tx(group, port, ttl=2):
     def _(data):
         return sk.sendto(data, (group, port))
     return _
+"""
 
 
-def txloop(pkt):
-    tx = open_tx(group4, port)
+def txloop(ctx, sk, pkt):
+    print("txloop ...")
     i = 0
     while 1:
+        if ctx.err():
+            raise ctx.err()
         i += 1
         pkt_ = pkt + (b'%d' % i)
         print("tx: %r ..." % pkt_)
-        tx(pkt + (b'%d' % i))
+        sk.send(pkt + (b'%d' % i))
         time.sleep(1)
 
-def rxloop():
-    rx = open_rx(group4, port)
+def rxloop(ctx, sk):
+    print("rxloop ...")
     while 1:
-        pkt = rx()
+        if ctx.err():
+            raise ctx.err()
+        pkt = sk.recv(4096)
         print("rx: %r" % pkt)
 
 
 def main():
+    sk = mjoin(group4, port)
     action = sys.argv[1]
-    if action == "tx":
-        txloop(sys.argv[2])
-    elif action == "rx":
-        rxloop()
-    else:
-        raise RuntimeError("Unknown action %r" % action)
-
-
 
+    wg = sync.WorkGroup(context.background())
+    if "tx" in action:
+        wg.go(txloop, sk, b(sys.argv[2]))
+    if "rx" in action:
+        wg.go(rxloop, sk)
 
+    wg.wait()
 
 if __name__ == '__main__':
     main()