proto/msgpack: Fix handshake magic

This fixes the basic NEO handshake in msgpack encoding.

go/neo/neonet/newlink.go

@@ -216,7 +216,7 @@ func _handshakeServer(ctx context.Context, conn net.Conn, version uint32) (enc p
 // handshake hello:
 //
 // - 00 00 00 <ver>	for 'N' encoding, and
-// - 92 c4 03 NEO ...	for 'M' encoding (= msgpack of (b"NEO", <ver>))
+// - 92 a3 NEO ...	for 'M' encoding (= msgpack of (b"NEO", <ver>))
 //
 // the first byte is different from TLS handshake (0x16).
 
@@ -234,9 +234,9 @@ func txHello(errctx string, conn net.Conn, version uint32, enc proto.Encoding) (
 		b[3] = uint8(version)
 
 	case 'M':
-		// (b"NEO", <V>) encoded as msgpack (= 92 c4 03 NEO int(<V>))
+		// (b"NEO", <V>) encoded as msgpack (= 92 a3 NEO int(<V>))
 		b = msgp.AppendArrayHeader(b, 2)       // 92
-		b = msgp.AppendBytes(b, []byte("NEO")) // c4 03 NEO
+		b = msgp.AppendString(b, "NEO")        // a3 NEO
 		b = msgp.AppendUint32(b, version)      // u?intX version
 
 	default:
@@ -269,24 +269,20 @@ func rxHello(errctx string, rx *xbufReader) (enc proto.Encoding, version uint32,
 		peerEnc = 'N'
 		peerVer = uint32(b[3])
 
-	case bytes.Equal(b, []byte{0x92, 0xc4, 3, 'N'}): // start of "fixarray<2> bin8 'N | EO' ...
+	case bytes.Equal(b, []byte{0x92, 0xa3, 'N', 'E'}): // start of "fixarray<2> bin8 'NE | O' ...
 		b = append(b, []byte{0,0}...)
 		_, err = io.ReadFull(rx, b[4:])
 		err = xio.NoEOF(err)
 		if err != nil {
 			return 0, 0, err
 		}
-		if !bytes.Equal(b[4:], []byte{'E','O'}) {
+		if !bytes.Equal(b[4:5], []byte{'O'}) {
 			badMagic = true
 			break
 		}
 
 		peerEnc = 'M'
-		rxM := msgp.Reader{R: rx.Reader}
-		peerVer, err = rxM.ReadUint32()
-		if err != nil {
-			return 0, 0, fmt.Errorf("M: recv peer version: %s", err) // XXX + "read magic" ctx
-		}
+		peerVer = uint32(b[5])
 
 	default:
 		badMagic = true