core-andrid/README.md

core-android

Topics

1. Introduciton
2. Disclaimer
3. Current features
4. Build from gomobile
5. Implementation
6. Indentified issues

Introduction

Testing playground to support the peernet protocol on android phones. The implementation above is a proof of concept android application. There is currently no modifications done to the peernet core to get it running on android phones. As a brief the entire project is done using Kotlin with Go mobile.

Screenshots:

Disclaimer:

It is important to note that there could be scenarios where the phone could potencially freeze. The current commits are currently unstable.

Current Features:

• Upload file to peernet
  1. Add files to warehouse
  2. Add file to blockchain
• Download file from peernet
• View latest files uploaded

Build from gomobile:

The following steps below demonstrate how to build the application:

• Create go project with the package called mobile

## The following applies for linux 
- mkdir mobile 
- cd mobile/
- go mod init <module name>
- touch mobile.go

• add to mobile.go

package mobile

import (
	"fmt"
	"github.com/PeernetOfficial/core"
	"github.com/PeernetOfficial/core/webapi"
	"github.com/google/uuid"
	"net/http"
	"time"
)

// MobileMain The following function is called as a bind function
// from the Kotlin implementation
func MobileMain(path string) {

	var config core.Config

	// Load the config file
	core.LoadConfig(path+"Config.yaml", &config)

	//Setting modified paths in the config file
	config.SearchIndex = path + "data/search_Index/"
	config.BlockchainGlobal = path + "data/blockchain/"
	config.BlockchainMain = path + "data/blockchain_main/"
	config.WarehouseMain = path + "data/warehouse/"
	config.GeoIPDatabase = path + "data/GeoLite2-City.mmdb"
	config.LogFile = path + "data/log.txt"
    
	// save modified config changes
	core.SaveConfig(path+"Config.yaml", &config)

	backendInit, status, err := core.Init("Your application/1.0", path+"Config.yaml", nil)
	if status != core.ExitSuccess {
		fmt.Printf("Error %d initializing config: %s\n", status, err.Error())
		return
	}

	// start config api server
	webapi.Start(backendInit, []string{"127.0.0.1:5125"}, false, "", "", 10*time.Second, 10*time.Second, uuid.Nil)

	backendInit.Connect()

	// Checks if the go code can access the internet
	if !connected() {
		fmt.Print("Not connected to the internet ")
	} else {
		fmt.Print("Connected")
	}

}

func connected() (ok bool) {
	_, err := http.Get("http://clients3.google.com/generate_204")
	if err != nil {
		return false
	}
	return true
}

• Install go mobile

go install golang.org/x/mobile/cmd/gomobile@latest

• Initialize go mobile

gomobile init

• Add path for Android NDK

export ANDROID_HOME=$HOME/Android/Sdk

• Generate .aar and .jar file

gomobile bind -target android .

Output:
mobile.aar  mobile-sources.jar

• clone the following repo

git clone https://github.com/PeernetOfficial/core-android

• add the following files(i.e mobile.aar,mobile-sources.jar) to the following path. Overwrite it if the file already exists

/<path of the repo>/core-android/app/libs/

• Open the project in android studio and click the play button.

Implementation

• // Todo

Indentified issues

The core-android only supports upto Android API level 29.

Api level 30 issue

The following is a list of the ways that apps are affected by this change (from Api level 30 onwards):

• NetworkInterface.getHardwareAddress() returns null for every interface.
• Apps cannot use the bind() function on NETLINK_ROUTE sockets.
• The ip command does not return information about interfaces.
• Apps cannot send RTM_GETLINK messages.

source (https://developer.android.com/training/articles/user-data-ids#mac-11-plus)

Possible solution

" SDK 30 prohibits syscall.NetlinkRIB(syscall.RTM_GETADDR, ...) which Go's net.Interfaces uses. Implement an Android specific version of net.Interfaces to use instead.

Passing primitive types across JNI is relatively straightforward, passing a single object of a complex class is annoying but still possible, but passing lists and other more complex data structures is way harder. As such, this commit added a Java routine to render the interface information to a string and pass that across JNI as a primitive type for Go code to parse. " PR with a solution: https://github.com/tailscale/tailscale-android/pull/21

Track issue