[lbry] rpcclient: add a blocknotify example using lbcd websocket

rpcclient/examples/lbcdblocknotify/README.md

@@ -0,0 +1,46 @@
+# lbcd Websockets Example
+
+This example shows how to use the rpcclient package to connect to a btcd RPC
+server using TLS-secured websockets, register for block connected and block
+disconnected notifications, and get the current block count.
+
+## Running the Example
+
+The first step is to clone the lbcd package:
+
+```bash
+$ git clone github.com/lbryio/lbcd
+```
+
+Display available options:
+
+```bash
+$ go run . -h
+
+  -coinid string
+        Coin ID (default "1425")
+  -rpcpass string
+        LBCD RPC password (default "rpcpass")
+  -rpcserver string
+        LBCD RPC server (default "localhost:9245")
+  -rpcuser string
+        LBCD RPC username (default "rpcuser")
+  -stratum string
+        Stratum server (default "lbrypool.net:3334")
+  -stratumpass string
+        Stratum server password (default "password")
+```
+
+Start the program:
+
+```bash
+$ go run . -stratumpass <STRATUM PASSWD> -rpcuser <RPC USERNAME> -rpcpass <RPC PASSWD>
+
+2022/01/10 23:16:21 NotifyBlocks: Registration Complete
+2022/01/10 23:16:21 Block count: 1093112
+...
+```
+
+## License
+
+This example is licensed under the [copyfree](http://copyfree.org) ISC License.

rpcclient/examples/lbcdblocknotify/main.go

@@ -0,0 +1,105 @@
+// Copyright (c) 2014-2017 The btcsuite developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net"
+	"path/filepath"
+
+	"github.com/lbryio/lbcd/rpcclient"
+	"github.com/lbryio/lbcd/wire"
+	"github.com/lbryio/lbcutil"
+)
+
+func send(stratum, stratumPass, coinid, blockHash string) error {
+	addr, err := net.ResolveTCPAddr("tcp", stratum)
+	if err != nil {
+		return fmt.Errorf("can't resolve addr: %w", err)
+	}
+
+	conn, err := net.DialTCP("tcp", nil, addr)
+	if err != nil {
+		return fmt.Errorf("can't dial tcp: %w", err)
+	}
+	defer conn.Close()
+
+	msg := fmt.Sprintf(`{"id":1,"method":"mining.update_block","params":[%q,%q,%q]}`,
+		stratumPass, coinid, blockHash)
+
+	_, err = conn.Write([]byte(msg))
+	if err != nil {
+		return fmt.Errorf("can't write message: %w", err)
+	}
+
+	return nil
+}
+
+func main() {
+
+	var (
+		coinid      = flag.String("coinid", "1425", "Coin ID")
+		stratum     = flag.String("stratum", "lbrypool.net:3334", "Stratum server")
+		stratumPass = flag.String("stratumpass", "password", "Stratum server password")
+		rpcserver   = flag.String("rpcserver", "localhost:9245", "LBCD RPC server")
+		rpcuser     = flag.String("rpcuser", "rpcuser", "LBCD RPC username")
+		rpcpass     = flag.String("rpcpass", "rpcpass", "LBCD RPC password")
+		notls       = flag.Bool("notls", false, "Connect to LBCD with TLS disabled")
+	)
+
+	flag.Parse()
+
+	ntfnHandlers := rpcclient.NotificationHandlers{
+		OnFilteredBlockConnected: func(height int32, header *wire.BlockHeader, txns []*lbcutil.Tx) {
+
+			blockHash := header.BlockHash().String()
+
+			log.Printf("Block connected: %v (%d) %v", blockHash, height, header.Timestamp)
+
+			if err := send(*stratum, *stratumPass, *coinid, blockHash); err != nil {
+				log.Printf("ERROR: failed to notify stratum: %s", err)
+			}
+		},
+	}
+
+	// Connect to local lbcd RPC server using websockets.
+	lbcdHomeDir := lbcutil.AppDataDir("lbcd", false)
+	certs, err := ioutil.ReadFile(filepath.Join(lbcdHomeDir, "rpc.cert"))
+	if err != nil {
+		log.Fatalf("can't read lbcd certificate: %s", err)
+	}
+	connCfg := &rpcclient.ConnConfig{
+		Host:         *rpcserver,
+		Endpoint:     "ws",
+		User:         *rpcuser,
+		Pass:         *rpcpass,
+		Certificates: certs,
+		DisableTLS:   *notls,
+	}
+	client, err := rpcclient.New(connCfg, &ntfnHandlers)
+	if err != nil {
+		log.Fatalf("can't create rpc client: %s", err)
+	}
+
+	// Register for block connect and disconnect notifications.
+	if err = client.NotifyBlocks(); err != nil {
+		log.Fatalf("can't register block notification: %s", err)
+	}
+	log.Printf("NotifyBlocks: Registration Complete")
+
+	// Get the current block count.
+	blockCount, err := client.GetBlockCount()
+	if err != nil {
+		log.Fatalf("can't get block count: %s", err)
+	}
+	log.Printf("Block count: %d", blockCount)
+
+	// Wait until the client either shuts down gracefully (or the user
+	// terminates the process with Ctrl+C).
+	client.WaitForShutdown()
+}