client: implement rudimentary zmq client

client/README.md

@@ -0,0 +1,2 @@
+`# apt-get install libzmq3-dev`
+`$ go get github.com/pebbe/zmq4`

client/zmq_client.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"encoding/binary"
+	"log"
+
+	"github.com/gtank/ctxd/parser"
+	zmq "github.com/pebbe/zmq4"
+	"github.com/pkg/errors"
+)
+
+const (
+	PORT = 28332
+)
+
+func main() {
+	ctx, err := zmq.NewContext()
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer ctx.Term()
+
+	// WARNING: The Socket is not thread safe. This means that you cannot
+	// access the same Socket from different goroutines without using something
+	// like a mutex.
+	sock, err := ctx.NewSocket(zmq.SUB)
+	if err != nil {
+		log.Fatal(errors.Wrap(err, "creating socket"))
+	}
+	err = sock.SetSubscribe("rawblock")
+	if err != nil {
+		log.Fatal(errors.Wrap(err, "subscribing"))
+	}
+	err = sock.Connect("tcp://127.0.0.1:28332")
+	if err != nil {
+		log.Fatal(errors.Wrap(err, "connecting"))
+	}
+	defer sock.Close()
+
+	for {
+		msg, err := sock.RecvMessageBytes(0)
+		if err != nil {
+			log.Println(errors.Wrap(err, "on message receipt"))
+			continue
+		}
+
+		if len(msg) < 3 {
+			log.Printf("got unknown msg: %v", msg)
+			continue
+		}
+
+		topic, body := msg[0], msg[1]
+
+		var sequence int
+		if len(msg[2]) == 4 {
+			sequence = int(binary.LittleEndian.Uint32(msg[len(msg)-1]))
+		}
+
+		switch string(topic) {
+		case "rawblock":
+			log.Printf("got block (%d): %x\n", sequence, body[:80])
+			go handleBlock(sequence, body)
+		default:
+			log.Printf("unexpected topic: %s (%d)", topic, sequence)
+		}
+	}
+}
+
+func handleBlock(sequence int, blockData []byte) {
+	block := parser.NewBlock()
+	rest, err := block.ParseFromSlice(blockData)
+	if err != nil {
+		log.Println("Error parsing block (%d): %v", err)
+		return
+	}
+	if len(rest) != 0 {
+		log.Println("Received overlong message:\n%x", rest)
+		return
+	}
+
+	log.Printf("Received a version %d block with %d transactions.", block.GetVersion(), block.GetTxCount())
+}

go.mod

@@ -2,7 +2,8 @@ module github.com/gtank/ctxd
 
 require (
 	github.com/golang/protobuf v1.2.0
+	github.com/pebbe/zmq4 v1.0.0
 	github.com/pkg/errors v0.8.0
-	golang.org/x/net v0.0.0-20180926154720-4dfa2610cdf3 // indirect
+	golang.org/x/net v0.0.0-20180926154720-4dfa2610cdf3
-	golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f // indirect
+	google.golang.org/grpc v1.15.0
 )

go.sum

@@ -1,8 +1,31 @@
+cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
+github.com/golang/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:tluoj9z5200jBnyusfRPU2LqT6J+DAorxEvtC7LHB+E=
+github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
 github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
+github.com/pebbe/zmq4 v1.0.0 h1:D+MSmPpqkL5PSSmnh8g51ogirUCyemThuZzLW7Nrt78=
+github.com/pebbe/zmq4 v1.0.0/go.mod h1:7N4y5R18zBiu3l0vajMUWQgZyjv464prE8RCyBcmnZM=
 github.com/pkg/errors v0.8.0 h1:WdK/asTD0HN+q6hsWO3/vpuAkAr+tw6aNJNDFFf0+qw=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+golang.org/x/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
+golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180926154720-4dfa2610cdf3 h1:dgd4x4kJt7G4k4m93AYLzM8Ni6h2qLTfh9n9vXJT3/0=
 golang.org/x/net v0.0.0-20180926154720-4dfa2610cdf3/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f h1:wMNYb4v58l5UBM7MYRLPG6ZhfOqbKu7X5eyFl8ZhKvA=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20180830151530-49385e6e1522 h1:Ve1ORMCxvRmSXBwJK+t3Oy+V2vRW2OetUQBq4rJIkZE=
+golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/tools v0.0.0-20180828015842-6cd1fcedba52/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
+google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8 h1:Nw54tB0rB7hY/N0NQvRW8DG4Yk3Q6T9cu9RcFQDu1tc=
+google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
+google.golang.org/grpc v1.15.0 h1:Az/KuahOM4NAidTEuJCv/RonAA7rYsTPkqXVjr+8OOw=
+google.golang.org/grpc v1.15.0/go.mod h1:0JHn/cJsOMiMfNA9+DeHDlAU7KAAB5GDlYFpa9MZMio=
+honnef.co/go/tools v0.0.0-20180728063816-88497007e858/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

parser/block.go

@@ -16,6 +16,14 @@ func NewBlock() *block {
 	return &block{}
 }
 
+func (b *block) GetVersion() int {
+	return int(b.hdr.Version)
+}
+
+func (b *block) GetTxCount() int {
+	return len(b.vtx)
+}
+
 func (b *block) ParseFromSlice(data []byte) (rest []byte, err error) {
 	hdr := NewBlockHeader()
 	data, err = hdr.ParseFromSlice(data)