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main.go
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main.go
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package main
import (
"context"
"flag"
"github.com/INFURA/go-ethlibs/eth"
"github.com/INFURA/go-ethlibs/jsonrpc"
"github.com/INFURA/go-ethlibs/node"
"log"
)
var (
target = flag.String("target", "", "target URL")
)
func main() {
flag.Parse()
target := *target
if target == "" {
log.Fatalf("[FATAL] Target is required")
return
}
ctx := context.Background()
log.Printf("[INFO] Connecting to: %s", target)
client, err := node.NewClient(ctx, target)
if err != nil {
log.Fatalf("[FATAL] Client error: %v", err)
}
num, err := client.BlockNumber(ctx)
if err != nil {
log.Fatalf("[FATAL] BlockNumber error: %v", err)
}
log.Printf("[INFO] Current Block number: %d", num)
if client.IsBidirectional() {
log.Printf("[INFO] Client supports subscriptions")
log.Printf("[INFO] starting newHeads subscription...")
newHeads, err := client.SubscribeNewHeads(ctx)
if err != nil {
log.Fatalf("[FATAL] NewHeads error: %v", err)
}
log.Printf("[INFO] newHeads subscription id %s", newHeads.ID())
log.Printf("[INFO] waiting for newHeads subscription notifications...")
received := 0
for notif := range newHeads.Ch() {
newHead := eth.NewHeadsNotificationParams{}
err := notif.UnmarshalParamsInto(&newHead)
if err != nil {
log.Fatalf("[FATAL] Cannot parse newHeads params: %v", err)
}
// get the full block details, using a custom jsonrpc ID as a test
block, err := client.BlockByHash(
node.ContextWithRequestID(ctx, jsonrpc.StringID("test")), newHead.Result.Hash.String(),
true,
)
if err != nil {
log.Fatalf("[FATAL] Block for newHead notification not found: %v", err)
}
log.Printf("[INFO] got notification for new block %v %v", block.Number.UInt64(), block.Hash)
received += 1
// unsubscribe after 3rd block (just as a test)
if received == 3 {
if err := newHeads.Unsubscribe(ctx); err != nil {
log.Fatalf("[FATAL] error unsubscribing newHeads: %v", err)
}
}
}
// we'll do a logs subscription as soon as the newHeads one is done
log.Printf("[INFO] starting logs subscription...")
logs, err := client.Subscribe(ctx, &jsonrpc.Request{
JSONRPC: "2.0",
Method: "eth_subscribe",
ID: jsonrpc.ID{
Num: 2,
},
Params: jsonrpc.MustParams("logs", ð.LogFilter{}),
})
if err != nil {
log.Fatalf("[FATAL] Logs subscription error: %v", err)
}
log.Printf("[INFO] logs subscription id %s", logs.ID())
log.Printf("[INFO] waiting for logs subscription notification...")
for notif := range logs.Ch() {
log.Printf("[INFO] Logs result: %s", string(notif.Params))
// unsubscribe after first logs (just as a test)
if err := logs.Unsubscribe(ctx); err != nil {
log.Fatalf("[FATAL] error unsubscribing logs: %v", err)
}
}
}
}