Get Multicast Dest from Python Socket Recv

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For my project, I need some way to know which multicast group a packet was originally sent to when it's received by my client. I've considered maintaining a map of sockets to multicast groups and identifying them this way, but surely there's some way to get the address from the datagram?

To listen, I'm currently using:

# Initialise socket for IPv6 datagrams

sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, socket.IPPROTO_UDP)



# Allows address to be reused

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)



# Binds to all interfaces on the given port

sock.bind(('', 8080))



# Allow messages from this socket to loop back for development

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True)



# Construct message for joining multicast group

mreq = struct.pack("16s15s".encode('utf-8'), socket.inet_pton(socket.AF_INET6, "ff02::abcd:1"), (chr(0) * 16).encode('utf-8'))

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)



data, addr = sock.recvfrom(1024)

and to send:

# Create ipv6 datagram socket

sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)

# Allow own messages to be sent back (for local testing)

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True)

sock.sendto("hello world".encode('utf-8'), ("ff02::abcd:1", 8080))

Which works, but the address when received is that of the sending machine. How can I see the multicast group it was sent to?

Thanks!

edited Nov 26 '18 at 20:00

asked Nov 26 '18 at 19:38

Jordan Mackie

4261523

add a comment |

To listen, I'm currently using:

# Initialise socket for IPv6 datagrams

sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, socket.IPPROTO_UDP)



# Allows address to be reused

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)



# Binds to all interfaces on the given port

sock.bind(('', 8080))



# Allow messages from this socket to loop back for development

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True)



# Construct message for joining multicast group

mreq = struct.pack("16s15s".encode('utf-8'), socket.inet_pton(socket.AF_INET6, "ff02::abcd:1"), (chr(0) * 16).encode('utf-8'))

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)



data, addr = sock.recvfrom(1024)

and to send:

# Create ipv6 datagram socket

sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)

# Allow own messages to be sent back (for local testing)

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True)

sock.sendto("hello world".encode('utf-8'), ("ff02::abcd:1", 8080))

Which works, but the address when received is that of the sending machine. How can I see the multicast group it was sent to?

Thanks!

edited Nov 26 '18 at 20:00

asked Nov 26 '18 at 19:38

Jordan Mackie

4261523

add a comment |

To listen, I'm currently using:

# Initialise socket for IPv6 datagrams

sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, socket.IPPROTO_UDP)



# Allows address to be reused

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)



# Binds to all interfaces on the given port

sock.bind(('', 8080))



# Allow messages from this socket to loop back for development

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True)



# Construct message for joining multicast group

mreq = struct.pack("16s15s".encode('utf-8'), socket.inet_pton(socket.AF_INET6, "ff02::abcd:1"), (chr(0) * 16).encode('utf-8'))

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)



data, addr = sock.recvfrom(1024)

and to send:

# Create ipv6 datagram socket

sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)

# Allow own messages to be sent back (for local testing)

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True)

sock.sendto("hello world".encode('utf-8'), ("ff02::abcd:1", 8080))

Which works, but the address when received is that of the sending machine. How can I see the multicast group it was sent to?

Thanks!

edited Nov 26 '18 at 20:00

asked Nov 26 '18 at 19:38

Jordan Mackie

4261523

To listen, I'm currently using:

# Initialise socket for IPv6 datagrams

sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, socket.IPPROTO_UDP)



# Allows address to be reused

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)



# Binds to all interfaces on the given port

sock.bind(('', 8080))



# Allow messages from this socket to loop back for development

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True)



# Construct message for joining multicast group

mreq = struct.pack("16s15s".encode('utf-8'), socket.inet_pton(socket.AF_INET6, "ff02::abcd:1"), (chr(0) * 16).encode('utf-8'))

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, mreq)



data, addr = sock.recvfrom(1024)

and to send:

# Create ipv6 datagram socket

sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)

# Allow own messages to be sent back (for local testing)

sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True)

sock.sendto("hello world".encode('utf-8'), ("ff02::abcd:1", 8080))

Which works, but the address when received is that of the sending machine. How can I see the multicast group it was sent to?

Thanks!

python python-3.x sockets udp multicast

edited Nov 26 '18 at 20:00

asked Nov 26 '18 at 19:38

Jordan Mackie

4261523

edited Nov 26 '18 at 20:00

asked Nov 26 '18 at 19:38

Jordan Mackie

4261523

edited Nov 26 '18 at 20:00

asked Nov 26 '18 at 19:38

Jordan Mackie

4261523

asked Nov 26 '18 at 19:38

Jordan Mackie

4261523

asked Nov 26 '18 at 19:38

Jordan Mackie

4261523

add a comment |

1 Answer
1

active

oldest

votes

You only joined multicast group address "ff02::abcd:1". Therefore, any packet that is received on the socket must have been sent to that multicast address.

answered Jan 8 at 15:07

Bruno Rijsman

1,70331936

Thanks Bruno. I understand that, I'm trying to solve the problem for one socket that joins multiple multicast groups though.

– Jordan Mackie
Jan 9 at 20:00

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

You only joined multicast group address "ff02::abcd:1". Therefore, any packet that is received on the socket must have been sent to that multicast address.

answered Jan 8 at 15:07

Bruno Rijsman

1,70331936

Thanks Bruno. I understand that, I'm trying to solve the problem for one socket that joins multiple multicast groups though.

– Jordan Mackie
Jan 9 at 20:00

add a comment |

You only joined multicast group address "ff02::abcd:1". Therefore, any packet that is received on the socket must have been sent to that multicast address.

answered Jan 8 at 15:07

Bruno Rijsman

1,70331936

Thanks Bruno. I understand that, I'm trying to solve the problem for one socket that joins multiple multicast groups though.

– Jordan Mackie
Jan 9 at 20:00

add a comment |

You only joined multicast group address "ff02::abcd:1". Therefore, any packet that is received on the socket must have been sent to that multicast address.

answered Jan 8 at 15:07

Bruno Rijsman

1,70331936

You only joined multicast group address "ff02::abcd:1". Therefore, any packet that is received on the socket must have been sent to that multicast address.

answered Jan 8 at 15:07

Bruno Rijsman

1,70331936

answered Jan 8 at 15:07

Bruno Rijsman

1,70331936

answered Jan 8 at 15:07

Bruno Rijsman

1,70331936

answered Jan 8 at 15:07

Bruno Rijsman

1,70331936

Thanks Bruno. I understand that, I'm trying to solve the problem for one socket that joins multiple multicast groups though.

– Jordan Mackie
Jan 9 at 20:00

add a comment |

Thanks Bruno. I understand that, I'm trying to solve the problem for one socket that joins multiple multicast groups though.

– Jordan Mackie
Jan 9 at 20:00

Thanks Bruno. I understand that, I'm trying to solve the problem for one socket that joins multiple multicast groups though.

– Jordan Mackie
Jan 9 at 20:00

add a comment |

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