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70 lines
2.8 KiB
Markdown
70 lines
2.8 KiB
Markdown
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# How to connect two Peers by key with Hyperdht
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Get setup by creating a project folder and installing dependencies:
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```bash
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mkdir connect-two-peers
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cd connect-two-peers
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pear init -y -t terminal
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npm install hyperdht b4a graceful-goodbye
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```
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[Hyperswarm](../building-blocks/hyperswarm.md) helps to find and connect to peers who are announcing a common 'topic'. The swarm topic can be anything. The HyperDHT uses a series of holepunching techniques to establish direct connections between peers, even if they're located on home networks with tricky NATs.
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In the HyperDHT, peers are identified by a public key, not by an IP address. With the public key, users can connect to each other irrespective of their location, even if they move between different networks.
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> Hyperswarm's holepunching will fail if both the client peer and the server peer are on randomizing [NATs](https://en.wikipedia.org/wiki/Network_address_translation), in which case the connection must be relayed through a third peer. Hyperswarm does not do any relaying by default.
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> For example, Keet implements its relaying system wherein other call participants can serve as relays -- the more participants in the call, the stronger overall connectivity becomes.
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Use the HyperDHT to create a basic CLI chat app where a client peer connects to a server peer by public key. This example consists of two files: `client.js` and `server.js`.
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`server.js` will create a key pair and then start a server that will listen on the generated key pair. The public key is logged into the console. Copy it for instantiating the client.
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```javascript
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//server.js
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import DHT from 'hyperdht'
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import goodbye from 'graceful-goodbye'
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import b4a from 'b4a'
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const dht = new DHT()
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// This keypair is the peer identifier in the DHT
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const keyPair = DHT.keyPair()
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const server = dht.createServer(conn => {
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console.log('got connection!')
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process.stdin.pipe(conn).pipe(process.stdout)
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})
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server.listen(keyPair).then(() => {
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console.log('listening on:', b4a.toString(keyPair.publicKey, 'hex'))
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})
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// Unnannounce the public key before exiting the process
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// (This is not a requirement, but it helps avoid DHT pollution)
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goodbye(() => server.close())
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```
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`client.js` will spin up a client, and the public key copied earlier must be supplied as a command line argument for connecting to the server. The client process will log `got connection` into the console when it connects to the server.
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Once it's connected, try typing in both terminals!
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``` javascript
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//client.js
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import DHT from 'hyperdht'
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import b4a from 'b4a'
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console.log('Connecting to:', process.argv[2])
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const publicKey = b4a.from(process.argv[2], 'hex')
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const dht = new DHT()
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const conn = dht.connect(publicKey)
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conn.once('open', () => console.log('got connection!'))
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process.stdin.pipe(conn).pipe(process.stdout)
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```
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