diff --git a/pkg/util/io_test.go b/pkg/util/binaryrw_test.go
similarity index 62%
rename from pkg/util/io_test.go
rename to pkg/util/binaryrw_test.go
index 7d0258eda..7bf320f20 100644
--- a/pkg/util/io_test.go
+++ b/pkg/util/binaryrw_test.go
@@ -12,9 +12,9 @@ func TestWriteVarUint1(t *testing.T) {
 		val = uint64(1)
 		buf = new(bytes.Buffer)
 	)
-	if err := WriteVarUint(buf, val); err != nil {
-		t.Fatal(err)
-	}
+	bw := BinWriter{W: buf}
+	bw.WriteVarUint(val)
+	assert.Nil(t, bw.Err)
 	assert.Equal(t, 1, buf.Len())
 }
 
@@ -23,13 +23,14 @@ func TestWriteVarUint1000(t *testing.T) {
 		val = uint64(1000)
 		buf = new(bytes.Buffer)
 	)
-
-	if err := WriteVarUint(buf, val); err != nil {
-		t.Fatal(err)
-	}
+	bw := BinWriter{W: buf}
+	bw.WriteVarUint(val)
+	assert.Nil(t, bw.Err)
 	assert.Equal(t, 3, buf.Len())
 	assert.Equal(t, byte(0xfd), buf.Bytes()[0])
-	res := ReadVarUint(buf)
+	br := BinReader{R: buf}
+	res := br.ReadVarUint()
+	assert.Nil(t, br.Err)
 	assert.Equal(t, val, res)
 }
 
@@ -38,13 +39,14 @@ func TestWriteVarUint100000(t *testing.T) {
 		val = uint64(100000)
 		buf = new(bytes.Buffer)
 	)
-
-	if err := WriteVarUint(buf, val); err != nil {
-		t.Fatal(err)
-	}
+	bw := BinWriter{W: buf}
+	bw.WriteVarUint(val)
+	assert.Nil(t, bw.Err)
 	assert.Equal(t, 5, buf.Len())
 	assert.Equal(t, byte(0xfe), buf.Bytes()[0])
-	res := ReadVarUint(buf)
+	br := BinReader{R: buf}
+	res := br.ReadVarUint()
+	assert.Nil(t, br.Err)
 	assert.Equal(t, val, res)
 }
 
@@ -53,12 +55,13 @@ func TestWriteVarUint100000000000(t *testing.T) {
 		val = uint64(1000000000000)
 		buf = new(bytes.Buffer)
 	)
-
-	if err := WriteVarUint(buf, val); err != nil {
-		t.Fatal(err)
-	}
+	bw := BinWriter{W: buf}
+	bw.WriteVarUint(val)
+	assert.Nil(t, bw.Err)
 	assert.Equal(t, 9, buf.Len())
 	assert.Equal(t, byte(0xff), buf.Bytes()[0])
-	res := ReadVarUint(buf)
+	br := BinReader{R: buf}
+	res := br.ReadVarUint()
+	assert.Nil(t, br.Err)
 	assert.Equal(t, val, res)
 }
diff --git a/pkg/util/io.go b/pkg/util/io.go
deleted file mode 100644
index d81491da3..000000000
--- a/pkg/util/io.go
+++ /dev/null
@@ -1,90 +0,0 @@
-package util
-
-import (
-	"encoding/binary"
-	"io"
-)
-
-// Variable length integer, can be encoded to save space according to the value typed.
-// len 1 uint8
-// len 3 0xfd + uint16
-// len 5 0xfe = uint32
-// len 9 0xff = uint64
-// For more information about this:
-// https://github.com/neo-project/neo/wiki/Network-Protocol
-
-// ReadVarUint reads a variable unsigned integer and returns it as a uint64.
-func ReadVarUint(r io.Reader) uint64 {
-	var b uint8
-	binary.Read(r, binary.LittleEndian, &b)
-	switch b {
-	case 0xfd:
-		var v uint16
-		binary.Read(r, binary.LittleEndian, &v)
-		return uint64(v)
-	case 0xfe:
-		var v uint32
-		binary.Read(r, binary.LittleEndian, &v)
-		return uint64(v)
-	case 0xff:
-		var v uint64
-		binary.Read(r, binary.LittleEndian, &v)
-		return v
-	default:
-		return uint64(b)
-	}
-}
-
-// WriteVarUint writes a variable unsigned integer.
-func WriteVarUint(w io.Writer, val uint64) error {
-	if val < 0xfd {
-		return binary.Write(w, binary.LittleEndian, uint8(val))
-	}
-	if val < 0xFFFF {
-		if err := binary.Write(w, binary.LittleEndian, byte(0xfd)); err != nil {
-			return err
-		}
-		return binary.Write(w, binary.LittleEndian, uint16(val))
-	}
-	if val < 0xFFFFFFFF {
-		if err := binary.Write(w, binary.LittleEndian, byte(0xfe)); err != nil {
-			return err
-		}
-		return binary.Write(w, binary.LittleEndian, uint32(val))
-	}
-
-	if err := binary.Write(w, binary.LittleEndian, byte(0xff)); err != nil {
-		return err
-	}
-
-	return binary.Write(w, binary.LittleEndian, val)
-}
-
-// ReadVarBytes reads a variable length byte array.
-func ReadVarBytes(r io.Reader) ([]byte, error) {
-	n := ReadVarUint(r)
-	b := make([]byte, n)
-	if err := binary.Read(r, binary.LittleEndian, b); err != nil {
-		return nil, err
-	}
-	return b, nil
-}
-
-// ReadVarString reads a variable length string.
-func ReadVarString(r io.Reader) (string, error) {
-	b, err := ReadVarBytes(r)
-	return string(b), err
-}
-
-// WriteVarString writes a variable length string.
-func WriteVarString(w io.Writer, s string) error {
-	return WriteVarBytes(w, []byte(s))
-}
-
-// WriteVarBytes writes a variable length byte array.
-func WriteVarBytes(w io.Writer, b []byte) error {
-	if err := WriteVarUint(w, uint64(len(b))); err != nil {
-		return err
-	}
-	return binary.Write(w, binary.LittleEndian, b)
-}