Subscribe to solutions

This example demonstrates how to subscribe to solutions from the bloXroute gateway. Only a subscriber with the correct private key can receive the solution.

Name: IntentSolutions

IntentSolutions is a GRPC stream of new solutions that match the dappAddress of the subscription as they are propagated in the BDN. IntentSolutionsRequest arguments:

Key	Description	Values
dappAddress	either ETH sender address or ETH address of DApp that should receive solutions	string
hash	Keccak256Hash of the dappAddress bytes	byte[]
signature	ECDSA signature of the hash signed by DApp private key	byte[]

IntentSolutionsReply fields (stream message):

Key	Description	Values
intentId	UUID of the intent	string
intentSolution	solution for the specific intent	byte[]
solutionId	UUID of the solution	string

Examples

gRPC - Golang

package main

import (
	"context"
	"encoding/hex"
	"fmt"
	"log"

	pb "github.com/bloXroute-Labs/gateway/v2/protobuf"

	"github.com/ethereum/go-ethereum/crypto"
	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
)

// gatewayHost is the address of the gateway to which the subscription is being made
const gatewayHost = "127.0.0.1:5002"

// header is the authorization header of your bloXroute Account
const header = "<YOUR-AUTHORIZATION-HEADER>"

func main() {
	// this will use localhost CA to verify the certificate
	creds := credentials.NewClientTLSFromCert(nil, "")

	// Dial the gateway
	conn, err := grpc.Dial(gatewayHost,
		grpc.WithTransportCredentials(creds),
		grpc.WithPerRPCCredentials(blxrCredentials{authorization: header}))
	if err != nil {
		log.Fatalln("dial grpc", err)
	}

	// Create a client
	client := pb.NewGatewayClient(conn)

	// Subscribe to solutions
	stream, err := client.IntentSolutions(context.Background(), genIntentSolutionRequest())
	if err != nil {
		log.Fatalln("subscribe to solutions", err)
	}

	for {
		fmt.Printf("listening for IntentSolutions from %s ...\n", gatewayHost)

		// Receive the solution from the stream until the stream is closed
		msg, err := stream.Recv()
		if err != nil {
			log.Fatalln("receive from stream", err)
		}

		fmt.Println("got solution:")
		fmt.Println("- intent_id:", msg.IntentId)
		fmt.Println("- solution_id:", msg.SolutionId)
		fmt.Println("- solution:", hex.EncodeToString(msg.IntentSolution))
	}
}

func genIntentSolutionRequest() *pb.IntentSolutionsRequest {
	// DApp private key used to prove the ownership of the DApp address
	const privateKeyHex = "7c4a8d09ca3762af61e59520943dc26494f8941e6e5b998321d3e84b8e4d3c16"

	// Convert the hex string to a private key
	privKey, err := crypto.HexToECDSA(privateKeyHex)
	if err != nil {
		log.Fatalln("error converting hex to ECDSA", err)
	}

	// Extract the public key
	pubKey := privKey.PublicKey
	signerAddress := crypto.PubkeyToAddress(pubKey)

	// Hash the signer address
	hash := crypto.Keccak256Hash([]byte(signerAddress.String())).Bytes() // need a hash to sign, so we're hashing the payload here
	sig, err := crypto.Sign(hash, privKey)                               // signing the hash
	if err != nil {
		log.Fatalln("error signing with private key", err)
	}

	// Return the solution request
	return &pb.IntentSolutionsRequest{
		DappAddress: signerAddress.String(),
		Hash:        hash,
		Signature:   sig,
	}
}

// blxrCredentials is an implementation of PerRPCCredentials
type blxrCredentials struct {
	authorization string
}

// GetRequestMetadata sets the authorization header
func (bc blxrCredentials) GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error) {
	return map[string]string{
		"authorization": bc.authorization,
	}, nil
}

// RequireTransportSecurity is a method of the PerRPCCredentials interface
func (bc blxrCredentials) RequireTransportSecurity() bool {
	return false
}

WS - Golang

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"

	"github.com/ethereum/go-ethereum/crypto"
	"github.com/gorilla/websocket"
)

func main() {
	dialer := websocket.DefaultDialer
	// Add the following lines if you work with IP instead of DNS
	// tlsConfig := &tls.Config{
	// 	Certificates:       []tls.Certificate{cert},
	// 	InsecureSkipVerify: true,
	// }
	// dialer.TLSClientConfig = tlsConfig

	req := generateIntentSolutionsRequest()

	wsSubscriber, _, err := dialer.Dial("wss://virginia.eth.blxrbdn.com/ws", http.Header{"Authorization": []string{"YOUR-AUTHORIZATION-HEADER"}})
	if err != nil {
		fmt.Println(err)
		return
	}

	err = wsSubscriber.WriteMessage(websocket.TextMessage, req)
	if err != nil {
		fmt.Println(err)
		return
	}

	for {
		_, nextNotification, err := wsSubscriber.ReadMessage()
		if err != nil {
			fmt.Println(err)
		}
		fmt.Println(string(nextNotification)) // or process it generally
	}
}

func generateIntentSolutionsRequest() []byte {
	// Generate an ECDSA key pair using secp256k1 curve
	privKey, err := crypto.GenerateKey()
	if err != nil {
		log.Fatalln("generate key", err)
	}

	pubKey := privKey.PublicKey                                        // extract the public key
	dappAddress := crypto.PubkeyToAddress(pubKey)                      // the address of the public key
	hash := crypto.Keccak256Hash([]byte(dappAddress.String())).Bytes() // need a hash to sign, so we're hashing the payload here
	sig, err := crypto.Sign(hash, privKey)                             // sign the hash
	if err != nil {
		log.Fatalln("sign privKey", err)
	}

	m := map[string]interface{}{
		"dapp_address": dappAddress.String(),
		"hash":         hash,
		"signature":    sig,
	}
	req, err := json.Marshal(m)
	if err != nil {
		log.Fatalln("marshal", err)
	}

	return []byte(fmt.Sprintf(`{ "id": "2", "method": "subscribe", "params": [ "userIntentSolutionsFeed", %s]}`, req))
}