lnd/mobile

Building mobile libraries

Prerequisites

Go language

• Install GO language.
• Provide $GOPATH to .zshrc or .bash_profile files.

export GOPATH=$HOME/go
export PATH=$PATH:$GOPATH/bin

Or any path you want it to be in.

Docker

• Install and run Docker.

Make

• Check that make is available by running the following command without errors:

⛰  make --version

Go mobile

• Install gomobile:

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

• Install gobind

⛰  go install golang.org/x/mobile/cmd/gobind@latest

Building the libraries

Note that gomobile only supports building projects from GOPATH at this point. So, before continuing, be sure to be in the src folder:

⛰  cd $GOPATH/src/github.com/lightningnetwork/lnd

To checkout the latest tagged release of lnd, run

⛰  git checkout $(git describe --tags --abbrev=0)

Or, the second option: just clone the project and checkout to any branch/tag (pay attention to the dot in the end).

⛰  git clone https://github.com/lightningnetwork/lnd .

For Android:

Move to the folder or create one:

⛰  cd $GOPATH/src/golang.org/x

After that clone the goland mobile repo

⛰  git clone https://github.com/golang/mobile

Building lnd for iOS

⛰  make ios

Building lnd for Android

Go to $GOPATH/src/github.com/lightningnetwork/lnd and run the command below (make sure that the Docker engine is running):

⛰  make android

make mobile will build both iOS and Android libraries.

Libraries

After the build has succeeded, the libraries will be found in mobile/build/ios/Lndmobile.xcframework and mobile/build/android/Lndmobile.aar. Reference your platforms' SDK documentation for how to add the library to your project.

Generating proto definitions

In order to call the methods in the generated library, the serialized proto for the given RPC call must be provided. Similarly, the response will be a serialized proto.

iOS

In order to generate protobuf definitions for iOS, add --swift_out=. to the first protoc invocation found in gen_protos.sh .

Then, some changes to Dockerfile need to be done in order to use the Swift protobuf plugin with protoc:

1. Replace the base image with FROM swift:focal so that Swift can be used.
2. clang-format='1:7.0*' is unavailable in Ubuntu Focal. Change that to clang-format='1:10.0*.
3. On the next line, install Go and set the environment variables by adding the following commands:

RUN apt-get install -y wget \
    && wget -c https://golang.org/dl/go1.17.3.linux-amd64.tar.gz -O - \
    | tar -xz -C /usr/local
ENV GOPATH=/go
ENV PATH=$PATH:/usr/local/go/bin:/go/bin

4. At the end of the file, just above CMD, add the following RUN command. This will download and compile the latest tagged release of Swift protobuf.

RUN git clone https://github.com/apple/swift-protobuf.git \
&& cd swift-protobuf \ 
&& git checkout $(git describe --tags --abbrev=0) \
&& swift build -c release \
&& mv .build/release/protoc-gen-swift /bin

Finally, run make rpc.

Tip: The generated Swift files will be found in various folders. If you’d like to move them to the same folder as the framework file, run

⛰  `find . -name "*.swift" -print0 | xargs -0 -I {} mv {} mobile/build/ios`.

Lndmobile.xcframework and all Swift files should now be added to your Xcode project. You will also need to add Swift Protobuf to your project to support the generated code.

Android

First option:

In order to generate protobuf definitions for Android, add --java_out=.

to the first protoc invocation found in gen_protos.sh . Then, run make rpc.

Second option (preferable):

• You have to install the profobuf plugin to your Android application. Please, follow this link https://github.com/google/protobuf-gradle-plugin.
• Add this line to your app build.gradle file.

classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.17"

• Create a proto folder under the main folder.

• Add aar file to libs folder.

• After that add these lines to your module's build.gradle file:

plugins {
    id "com.google.protobuf"
}

android {
    sourceSets {
        main {
            proto {

            }
        }
    }
}

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation "com.google.protobuf:protobuf-javalite:${rootProject.ext.javalite_version}"
}

protobuf {
    protoc {
        artifact = "com.google.protobuf:protoc:${rootProject.ext.protoc_version}"
    }
    generateProtoTasks {
        all().each { task ->
            task.builtins {
                java {
                    option "lite"
                }
            }
        }
    }
}

• Then, copy all the proto files from lnd/lnrpc to your proto folder, saving the structure.
• Build the project and wait until you see the generated Java proto files in the build folder.

Note:

If Android Studio tells you that the aar file cannot be included into the app-bundle, this is a workaround:

1. Create a separate gradle module
2. Remove everything from there and leave only aar and build.gradle.

3. Gradle file should countain only these lines:

configurations.maybeCreate("default")
artifacts.add("default", file('Lndmobile.aar'))

4. In dependencies add this line instead of depending on libs folder:

implementation project(":lndmobile", { "default" })

Options

Similar to lnd, subservers can be conditionally compiled with the build by setting the tags argument:

⛰  make ios

To support subservers that have APIs with name conflicts, pass the "prefix" flag. This will add the subserver name as a prefix to each method name:

⛰  make ios prefix=1

API docs

LND gRPC API Reference

TODO(halseth)