Decoding PHYPayload with /brocaar/lorawan repository on GitHub

Setup and configuration
1

Hi @brocaar!

I’m trying to decode PHYPayload inside PRStartReq messages captured with Wireshark, and thus be able to check some packets, but I’m not experienced with go so I can’t run the example (Lorawan10Decode) properly.
I’m still getting PHYPayload, AES18{} and LoRaWAN_10 as not defined.

2

Without providing any steps to reproduce your issue (code or commands), it is hard for me or anybody else to provide any help :slight_smile:

1 Like
3

I’m sorry, thought I had edited this a few hours ago. With go installed, I got the GitHub repository with go get command.
I have tried many things, as I saw different ways to use a function outside its package, but this is what I have now:

First thing I tried (as I said, not experienced) was copying the content of func ExamplePHYPayload_lorawan10Decode() in a ´main.go´ archive with imports in phypayload_test.go and main package. At that point, log reported non-declaration statement outside function body. Then I was told by a colleague to do as follows:

  1. Execute go init github.com/brocaar/lorawan inside $PATH folder which is /home/go/bin
  2. Then go tidy.
  3. Execute main.go file, which right now looks like this:
package main


import (
	"database/sql/driver"
	"encoding/base64"
	"encoding/hex"
	"fmt"
	"testing"

	. "github.com/smartystreets/goconvey/convey"
)
func ExamplePHYPayload_lorawan10Decode() {

	nwkSKey := [16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
	appSKey := [16]byte{16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1}

	var phy PHYPayload
	// use use UnmarshalBinary when decoding a byte-slice
	if err := phy.UnmarshalText([]byte("gAQDAgEDAAAGcwcK4mTU9+EX0sA=")); err != nil {
		panic(err)
	}

	ok, err := phy.ValidateUplinkDataMIC(LoRaWAN1_0, 0, 0, 0, nwkSKey, AES128Key{})
	if err != nil {
		panic(err)
	}
	if !ok {
		panic("invalid mic")
	}

	if err := phy.DecodeFOptsToMACCommands(); err != nil {
		panic(err)
	}

	phyJSON, err := phy.MarshalJSON()
	if err != nil {
		panic(err)
	}

	if err := phy.DecryptFRMPayload(appSKey); err != nil {
		panic(err)
	}
	macPL, ok := phy.MACPayload.(*MACPayload)
	if !ok {
		panic("*MACPayload expected")
	}

	pl, ok := macPL.FRMPayload[0].(*DataPayload)
	if !ok {
		panic("*DataPayload expected")
	}

	fmt.Println(string(phyJSON))
	fmt.Println(pl.Bytes)

	// Output:
	// {"mhdr":{"mType":"ConfirmedDataUp","major":"LoRaWANR1"},"macPayload":{"fhdr":{"devAddr":"01020304","fCtrl":{"adr":false,"adrAckReq":false,"ack":false,"fPending":false,"classB":false},"fCnt":0,"fOpts":[{"cid":"DevStatusReq","payload":{"battery":115,"margin":7}}]},"fPort":10,"frmPayload":[{"bytes":"4mTU9w=="}]},"mic":"e117d2c0"}
	// [1 2 3 4]
}

func main(){
      ExamplePHYPayload_lorawan10Decode()
}

I get undefined PHYPayload, LoRaWAN1_0 and AES128Key and I don’t know how to declare those variables, or If we need to do any change on the code, which I don’t think so because of other examples I’ve been reading.
Also, I see imported but not used for the imports, but I don’t know If that’s relevant.
I thing something related to GOBIN or GOPATH could be happening.
Again, sorry for my lack of experience, both my colleague and I are new in this whole project and also with Go language.

4

The proper way is to import the github.com/brocaar/lorawan code into your code. Then you can use structs and variables like lorawan.PHYPayload…

Please see How to Write Go Code - The Go Programming Language for more details.