diff --git a/protocol/protocol.go b/protocol/protocol.go
new file mode 100644
index 00000000..c4f2cb1a
--- /dev/null
+++ b/protocol/protocol.go
@@ -0,0 +1,116 @@
+package protocol
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	// "errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	// "os"
+)
+
+type (
+	MessageType byte
+	Integer     uint32
+	PieceIndex  Integer
+	PieceOffset Integer
+)
+
+const (
+	Choke MessageType = iota
+	Unchoke
+	Interested
+	NotInterested
+	Have
+	Bitfield
+	Request
+	Piece
+	Cancel
+)
+
+type Message struct {
+	KeepAlive bool
+	Type      MessageType
+	Bitfield  []bool
+	Index     PieceIndex
+	Begin     PieceOffset
+	Length    Integer
+	Piece     []byte
+}
+
+func (msg *Message) UnmarshalReader(r io.Reader) (err error) {
+	err = binary.Read(r, binary.BigEndian, &msg.Type)
+	switch err {
+	case nil:
+		msg.KeepAlive = false
+	case io.EOF:
+		msg.KeepAlive = true
+		err = nil
+		return
+	default:
+		return
+	}
+	switch msg.Type {
+	case Choke, Unchoke, Interested, NotInterested:
+	case Have:
+		err = binary.Read(r, binary.BigEndian, &msg.Index)
+	case Request, Cancel:
+		err = binary.Read(r, binary.BigEndian, &msg.Index)
+		if err != nil {
+			return
+		}
+		err = binary.Read(r, binary.BigEndian, &msg.Begin)
+		if err != nil {
+			return
+		}
+		err = binary.Read(r, binary.BigEndian, &msg.Length)
+	case Bitfield:
+		// var bf []byte
+		_, err = ioutil.ReadAll(r)
+		if err != nil {
+			return
+		}
+	case Piece:
+	default:
+		return fmt.Errorf("unknown type: %v", msg.Type)
+	}
+	return
+}
+
+func (msg *Message) MarshalBinary() (b []byte, err error) {
+	w := &bytes.Buffer{}
+	if msg.KeepAlive {
+		b = w.Bytes()
+		return
+	}
+	err = w.WriteByte(byte(msg.Type))
+	if err != nil {
+		return
+	}
+	switch msg.Type {
+	case Choke, Unchoke, Interested, NotInterested:
+	case Have:
+		err = binary.Write(w, binary.BigEndian, msg.Index)
+	case Request, Cancel:
+		err = binary.Write(w, binary.BigEndian, msg.Index)
+		if err != nil {
+			return
+		}
+		err = binary.Write(w, binary.BigEndian, msg.Begin)
+		if err != nil {
+			return
+		}
+		err = binary.Write(w, binary.BigEndian, msg.Length)
+	case Bitfield, Piece:
+		panic("unimplemented")
+	default:
+		err = errors.New("unknown type")
+		return
+	}
+	if err == nil {
+		b = w.Bytes()
+	}
+	return
+}
diff --git a/protocol/protocol_test.go b/protocol/protocol_test.go
new file mode 100644
index 00000000..32db2a62
--- /dev/null
+++ b/protocol/protocol_test.go
@@ -0,0 +1,12 @@
+package protocol
+
+import (
+	"testing"
+)
+
+func TestConstants(t *testing.T) {
+	// check that iota works as expected in the const block
+	if NotInterested != 3 {
+		t.FailNow()
+	}
+}