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This article shows you how to build a UDP service in nodejs, which is concise and easy to understand, which will definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

Introduction to 1.UDP

User Datagram Protocol, also known as user Datagram protocol

Like TCP, it is located at the network transport layer to process packets

The most important feature of UDP is no connection.

UDP transmission speed is fast.

UDP data transmission is unreliable

It does not provide the disadvantages of packet grouping, assembly and the inability to sort packets, that is, when a message is sent, it is impossible to know whether it has arrived safely.

Reliability should be the responsibility of the application layer

Supports one-to-one communication as well as one-to-many communication

Many key Internet applications use UDP

Such as DNS Domain name Service system, TFTP simple File transfer Protocol, DHCP dynamic Host setup Protocol, etc.

UDP is suitable for applications with high requirements for book reading and lax data quality.

Such as streaming media, real-time multiplayer games, real-time audio and video

1.1 TCP and UDP

| | UDP | TCP-- |-connection | Connectionless | connection-oriented speed | connection-oriented speed | No connection is required, but the speed is fast | slow destination host needs to establish a connection | one-to-one, one-to-many | only one-to-one bandwidth | UDP header is shorter, consumes less bandwidth | consumes more bandwidth (larger message) message boundary | Yes | No reliability | low | High order | disordered | ordered |

In fact, this disorder of UDP protocol is basically rare and usually occurs only when the network is very congested.

When do you use TCP? When do you use UDP?

Use UDP when the speed requirement is high, such as video chat, qq chat

Use TCP when there are high requirements for data security, such as data transfer and file download

If for video chat, choose TCP if picture quality is preferred, and choose UDP if fluency is priority.

1.2 three modes of transmission of UDP

UDP unicast

A mode of transmission in which a unicast address is a single destination.

Address range: 0.0.0.0 to 223.255.255.255

UDP broadcast

Restricted broadcast: it will not be routed and forwarded. If the IP address network field and host field are all 1, the address is 255.255.255.255.

Direct broadcast: it will be routed and forwarded. The network field of the IP address defines this network. The host field is usually 1, such as 192.168.10.255.

The destination address is all devices in the network

There are two kinds of address ranges.

UDP Multicast

Multicasting, also known as multicast, passes a set of information to a set of destination addresses.

Unicast one-to-many

Every packet in unicast communication has an exact IP address

For the same data, if there are multiple receivers, Server needs to send unicast packets with the same number of recipients.

When there are hundreds of recipients, it will be a great burden on Server at home.

Broadcast faces one-to-many

Broadcast packets are restricted to the local area network

Once a device sends broadcast data, all devices in the broadcast domain receive the packet and have to consume resources to process it. A large number of broadcast packets will consume network broadband and device resources.

In IPv6, the transmission mode of the broadcast is cancelled

Multicast faces one-to-many

Multicast is very suitable for an one-to-many model, and multicast data will be received only if it is added to a specific multicast member. When there are multiple multicast members, the source does not need to send multiple copies of the data, only one, and the multicast network equipment will forward or copy the multicast data according to the actual needs.

The data flow is sent only to the recipients (group members) who join the multicast group, and the devices that do not need the data will not receive the multicast traffic.

With the same multicast message, there is only one data on a link, which greatly improves the utilization of network resources.

2. Dgram module in Node

Node's dgram module is used to build UDP services

It is very easy to create UDP sockets using this module. Once created, UDP sockets can either send data as a client or receive data as a server.

Const dgram = require ('dgram') const socket = dgram.createSocket (' udp4') 2.1 socket method API description bind () bind port and host address () return Socket address object close () close Socket and stop listening send () send messages addMembership () add multicast member dropMembership () delete multicast member setBroadcast () set whether to enable broadcast setTTL () set Datagram lifetime setMulticastTTL () set multicast Datagram survival Time 2.2 Socket event API indicates that it is triggered when listening snooping is successful Trigger only once when message receives a message triggering error when an error occurs triggering close to close socket triggers #. Using Node to realize UDP unicast

Const dgram = require ('dgram') const socket = dgram.createSocket (' udp4') socket.on ('listening', () = > {console.log (' successful connection')})

If the client does not bind a port number, the operating system automatically assigns a port number; if a port number is specified, it cannot send messages until the listening event of socket succeeds

Sever.js

Const dgram = require ('dgram'); const server = dgram.createSocket (' udp4'); server.on ('listening', r = > {console.log (' connected successfully server:');}); server.on ('message', (msg, remoteAddress) = > {console.log (`successfully connected to ${remoteAddress.address}: ${remoteAddress.port} `); server.send (' server said: I got your message', remoteAddress.port);}) Server.on ('close', () = > {console.log (' error');}); server.bind (3000)

Client.js

Const dgram = require ('dgram'); const client = dgram.createSocket (' udp4'); client.on ('listening', () = > {const address = client.address (); console.log (`successfully connected to ${address.address}: ${address.port} `); / / Direct address: 192.168.10.255 change the last three bits to 255.255.255.255 client.send (' hello', 3000, 'localhost');}) Client.on ('message', (msg, remoteAddress) = > {console.log (`client said to have received a message from the server ${msg} `);}); client.on (' error', () = > {console.log ('server errord');}); client.bind (3200); 4. Use Node to implement UDP broadcast mode / / after listening successfully, turn on the broadcast mode server.on ('listening', () = > {server.setBroadcast (true)}) 5. Using Node to implement UDP Multicast

Server.js

/ / you only need to specify Multicast ip when sending messages. Server.on ('listening', () = > {server.send (' sending Multicast messages', 3300, '224.0.1.100 messages, (err) = > {console.log (err)})})

Client.js

Client.on ('listening', () = > {/ / the ip that joins a specific multicast group after listening successfully, and the client will receive the multicast data client.addMemberShip (' 224.0.1.100')}) the above content is how to build a UDP service in nodejs. Have you learned any knowledge or skills? If you want to learn more skills or enrich your knowledge reserve, you are welcome to follow the industry information channel.

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