How to send a socket to a multicast address?

How to send a socket to a multicast address?

Sending socket. In general, there’s nothing special you need to do on the sending end. The key is simply to send to a multicast IP (group) address. Tips: Use socket() with AF_INET and SOCK_DGRAM arguments as normal. Use bind() to associate this socket with a local address and port.

Why is multicast not received on VLAN 10?

1. fa0/15 of 3550-2 is a routed port connecting only to one host which only know how to send broadcast. 2. 3550-1 and 3550-2 only have one vlan 10. Broadcast was translated into multicast address, but multicast was not received on any vlan 10 access ports.

How to solve multicast not received by receiver?

Multicast not received by receiver. I have two layer3 switches, one vlan, and one routed port at 3550-1. 1. fa0/15 of 3550-2 is a routed port connecting only to one host which only know how to send broadcast. 2. 3550-1 and 3550-2 only have one vlan 10.

How to reduce the loss of multicast packets?

To make these changes permanent edit or create the /etc/sysctl.conf file and add the changes there. To reduce packet losses, the application must be able to take the date from the socket buffer before it is overwritten by the newest ones. Therefore, the socket level buffer should be increased.

How to use a receiving socket in multicast?

Receiving socket. Receiving is nearly the same, but with one additional system call: setsockopt(). Use socket() with AF_INET and SOCK_DGRAM arguments as normal. Use setsockopt() with the IP_ADD_MEMBERSHIP option. This tells the system to receive packets on the network whose destination is the group address (but not its own).

Why are Ports specified during a multicast subscription?

Only the traffic destined for your binded listening port will get passed up the TCP/IP stack to your app. In regards to why ports are specified during a multicast subscription – it’s because multicast IP is just that – IP only. “ports” are a property of the upper protocols (UDP and TCP).

What happens when you join a multicast group?

When you join a multicast group, you are configuring the NIC to listen for traffic sent to that same MAC address (in addition to its own). Without the hardware support, multicast wouldn’t be any more efficient than plain broadcast IP messages. The join operation also tells your router/gateway to forward multicast traffic from other networks.

What does it mean to bind a UDP socket?

The “bind” operation is basically saying, “use this local UDP port for sending and receiving data. In other words, it allocates that UDP port for exclusive use for your application. (Same holds true for TCP sockets).

How to join a multicast group in Linux?

Use the IP_ADD_MEMBERSHIP socket option to join the multicast group that receives the datagrams. When joining a group, specify the class D group address along with the IP address of a local interface. The system must call the IP_ADD_MEMBERSHIP socket option for each local interface receiving the multicast datagrams.

What does IP _ multicast _ LOOP DO in socket?

IP_MULTICAST_LOOP: Specifies whether or not a copy of an outgoing multicast datagram is delivered to the sending host as long as it is a member of the multicast group. The following examples enable a socket to send and receive multicast datagrams.

How to send multicast datagrams in Linux socket?

There are no restrictions on the location or number of members in a host group. A class D Internet address in the range 224.0.0.1 to 239.255.255.255 identifies a host group. An application program can send or receive multicast datagrams by using the socket () API and connectionless SOCK_DGRAM type sockets.

How many multicast groups are there in NetLink?

Each netlink family has a set of 32 multicast groups. When bind (2) is called on the socket, the nl_groups field in the sockaddr_nl should be set to a bit mask of the groups which it wishes to listen to. The default value for this field is zero which means that no multicasts will be received.

What does it mean to bind a multicast socket?

The “join multicast group” operation ( IP_ADD_MEMBERSHIP) is needed because it basically tells your network adapter to listen not only for ethernet frames where the destination MAC address is your own, it also tells the ethernet adapter ( NIC) to listen for IP multicast traffic as well for the corresponding multicast ethernet address.

How does the kernel assign a process ID to a netlink socket?

The kernel assigns the process ID to the first netlink socket the process opens and assigns a unique nl_pid to every netlink socket that the process subsequently creates. nl_groups is a bit mask with every bit representing a netlink group number. Each netlink family has a set of 32 multicast groups.

How to create a multicast socket in Linux?

Create an AF_INET, SOCK_DGRAM type socket. Initialize a sockaddr_in structure with the destination group IP address and port number. Set the IP_MULTICAST_LOOP socket option according to whether the sending system should receive a copy of the multicast datagrams that are transmitted.