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What is the fw:mDNS protocol, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain for you in detail, people with this need can come to learn, I hope you can gain something.

MDNS: a brief account of Multicast DNSmdns Protocol

Mdns is Multicast dns (Multicast DNS). MDNS mainly realizes the discovery and communication of hosts in LAN without traditional DNS server, using port 5353, complying with dns protocol, using existing DNS information structure, name syntax and resource record type. And no new operation code or response code is specified.

In the local area network, devices and devices need to know each other's ip address before they communicate with each other. In most cases, the ip of the device is not a static ip address, but an ip address dynamically assigned through the dhcp protocol. How to discover the device is to give full play to the mdns. For example, in the communication between the Internet of things and app, either app broadcasts or multicasts to send some specific information, and the device of interest answers. To realize the discovery of LAN devices, of course, mdns is much more powerful than this.

Multicast address: the multicast address uses a Class D address, with an address range of 224.0.0.0-239.255.255.255

A brief description of how mdns works:

Mdns uses the Multicast address: 224.0.0.251 (ipv6: FF02::FB) port 5353 MDNS is used within the LAN, and the domain name of the host ends with .local. Each host entering the LAN, if the mDNS service is enabled, will broadcast a message to all host groups in the LAN, who I am (domain name) and what my IP address is. Then other hosts with mdns services will respond and tell you who it is (domain name) and what its IP address is. Of course, when a device needs service, it uses mdns to query the domain name for the corresponding ip address. After receiving the message, the corresponding device also replies through multicast. At this time, other host devices can also receive the reply message, and other hosts will also record the domain name, ip and ttl, and update the cache.

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