diff --git a/protocol.go b/protocol.go
index 4e76d92..959b4df 100644
--- a/protocol.go
+++ b/protocol.go
@@ -200,11 +200,36 @@ func addPlayer(ws *websocket.Conn) {
 		return
 	}
 
-	gameParam := game.gameParam()
-	err = websocket.JSON.Send(ws, gameParam)
+	err = websocket.JSON.Send(ws,
+		[]string{"json", "jsonz", "gob"},
+	)
 	if err != nil {
-		log.Printf("%s %s game param parse error", gid.Id, player_id)
-		websocket.JSON.Send(ws, NewFailure("game param parse error"))
+		log.Printf("%s %s unable to send supported encodings msg", gid.Id, player_id)
+		websocket.JSON.Send(ws, NewFailure("encoding send error"))
+		return
+	}
+	var encoding string
+	err = websocket.JSON.Receive(ws, &encoding)
+	if err != nil {
+		log.Printf("%s %s unable to parse encoding", gid.Id, player_id)
+		websocket.JSON.Send(ws, NewFailure("encoding recieve error"))
+		return
+	}
+	log.Printf("negociated encoding: %s", encoding)
+	// TODO: use this negociated encoding
+
+	gameParam := game.gameParam()
+	gp := struct {
+		GameParam
+		Encoding string `json:"encoding"`
+	}{
+		GameParam: *gameParam,
+		Encoding:  encoding,
+	}
+	err = websocket.JSON.Send(ws, gp)
+	if err != nil {
+		log.Printf("%s %s game param send error", gid.Id, player_id)
+		websocket.JSON.Send(ws, NewFailure("game param send error"))
 		return
 	} else {
 		log.Printf("%s -> %s: sent %+v", gid.Id, player_id, gameParam)