DHT network is a protocol for distributed data storage and lookup. It obtains information from different nodes, allowing these nodes to share resources and form a network. The DHT network is a completely decentralized network that does not rely on any specific central node to provide services. In this article, we will explore how to implement a DHT network using Node.js.
What is DHT network?
DHT network is a network based on distributed hash table (Distributed Hash Table) built on the existing network. The DHT network enables decentralized data storage and search services between nodes, which means that it does not need to rely on a specific central node to provide services to other nodes like traditional networks.
The DHT network has the following characteristics:
DHT network is mainly used for P2P file sharing and search, distributed computing and distributed storage.
How to implement DHT network?
Implementing the DHT network requires completing the following tasks:
Here is an example of implementing a DHT network using Node.js:
We can use the crypto module Use the hash function in to generate the ID, such as SHA1:
const crypto = require('crypto'); function generateNodeId() { const nodeId = crypto.createHash('sha1') .update(`${Date.now()}_${Math.random()}`) .digest('hex') .substring(0, 20); return nodeId; }
When a node joins the network, it needs to generate the ID first, then send the joining information to other known nodes, and at the same time store the information of other nodes in the routing table middle.
const Node = require('./node'); const bootstrapNodes = [ { id: 'node1', address: '127.0.0.1:8001' }, { id: 'node2', address: '127.0.0.1:8002' } ]; const node = new Node(generateNodeId(), '127.0.0.1:8000'); for (const bootstrapNode of bootstrapNodes) { node.joinNetwork(bootstrapNode.id, bootstrapNode.address); }
We can use an array to implement the routing table, where each element represents a range of IDs, for example:
ID range | Node list |
---|---|
[0, 2^160/2^1) | [node1, node2] |
[node3, node4] | |
... |
class Node { // ... lookup(key, callback) { const targetId = getKeyId(key); const tableIds = getTableIds(targetId); const closestNodes = this.getClosestNodes(tableIds); const seenNodes = {}; const next = () => { const node = closestNodes.shift(); if (!node || seenNodes[node.id]) { return callback(null, null); } seenNodes[node.id] = true; if (node.id === this.id) { // key found return callback(null, this.store[key]); } else { // find key in next node this.findKeyInNode(node.id, targetId, (err, val) => { if (err || val) { return callback(err, val); } else { return next(); } }); } }; next(); } findKeyInNode(nodeId, targetId, callback) { // send find_key request to node // ... // callback with result if found } }
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