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This article mainly introduces the meaning of MultiCast in vxworks, which is very detailed and has certain reference value. Friends who are interested must finish reading it.

There are three ways to transfer UDP data: UniCast, MultiCast and BroadCast.

This MultiCast is generally called Multicast, or Multicast. The so-called multicast means that when a message needs to be sent to a multipoint destination, the source host sends only one data, and the destination address is the multicast group address. All members belonging to the group can receive a copy of the data sent by the source host. In this way, only the members who really need the information will receive the information, and other hosts will not receive it. Therefore, the multicast method not only solves the problem of repeated copy of data and repeated occupation of bandwidth in unicast mode, but also solves the waste of bandwidth resources in broadcast mode. The multicast IP address is used to identify an IP multicast group. IANA (Internet Assigned Number Authority) allocates class D address space to IP Multicast, which ranges from 224.0.0.0 to 239.255.255.255

224.0.0.00.224.0.0.255 reserved multicast address, that is, permanent group address

224.0.1.0 to 224.0.1.255 public multicast address, which can be used for Internet

224.0.2.00.238.255.255.255 Multicast address available to users, that is, temporary group address, which is valid throughout the network

239.0.0.0" 239.255.255.255 local management multicast address, valid only within a specific local scope

The commonly used reserved multicast addresses are

224.0.0.0 Base address (reserved)

224.0.0.1 addresses of all hosts

224.0.0.2 addresses of all Multicast routers

224.0.0.3 No allocation

224.0.0.4 DVMRP Router-Distance Vector MulticastRouting Protocol, distance Vector Multicast routing Protocol

224.0.0.5 OSPF Router-Open ShortestPath First, Open shortest path first

224.0.0.6 OSPF DR-Designated Router, designated router

224.0.0.7 ST Router-Shared Tree, shared Tr

224.0.0.8 ST host

224.0.0.9 RIP-2 Router

224.0.0.10 EIGRP Router-EnhancedInterior Gateway Routing Protocol, enhanced gateway internal routing line protocol

224.0.0.11 active Agent

224.0.0.12 DHCP Server / Relay Agent

224.0.0.13 all PIM routers-Protocol Independent Multicast, protocol independent multicast

224.0.0.14 RSVP Encapsulation-ResourceReservation Protocol, Resource Reservation Protocol

224.0.0.15 all CBT routers

224.0.0.16 specify SBM-SubnetworkBandwidth Management, subnet bandwidth management

224.0.0.17 all SBMs

224.0.0.18 VRRP-Virtual RouterRedundancy Protocol, virtual router redundancy protocol

239.255.255.255 SSDP protocol is used

Multiple nodes that join the same multicast group are equal to each other, regardless of whether Server or Client can receive or send data. However, it is customary to call the node that only receives data as Server, and the node that sends only data as Client.

The operation flow of Client is no different from that of UDP unicast.

Client calls socket () to open a Socket

Client specifies information such as IP and Port for multicast

Client calls sendto () to send data

Finally, Client calls close () to close Socket

The Server of multicast is slightly changed on the basis of unicast.

Server calls socket () to open a Socket

Server calls bind () to specify information such as Port

Server calls setsockopt () to join Multicast

Server calls recvfrom () to block reception

Server calls setsockopt () to exit Multicast

Finally, Server calls close () to close Socket

Write the simplest example

The Client side can directly use the UDP unicast programming example.

And Server is as follows, the key point is an IP_ADD_MEMBERSHIP.

The above is all the content of this article "what is the meaning of MultiCast in vxworks?" Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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