krosbridge A Kotlin ROS Client for rosbridge w @codeKK AndroidOpen Source Website

krosbridge

Introduction: A Kotlin ROS Client for rosbridge with an automatic code generator.

Tags:

A Kotlin ROS Client for rosbridge to publish/subscribe/call services with an automatic code generator for the required message/service data classes.

Features

Message API: Publish/Subscribe to Message Topics
Service API: Call/Advertise Services
ROS data classes: Pre-generated bases classes for ROS standard messages/services e.g. std_msg/Header
Code Generation of data classes: Use the ROS message (.msg) and service (.srv) files to automatically generate Kotlin data classes for easy usage.
Automatic Serialization: The (generated) Kotlin data classes are automatically serialized to JSON using the kotlinx.serialization
Websocket HTTP Client agnostic: Use any HTTP client for the Websocket connection. See here.
Coroutines API The implemented Service API uses Kotlin Coroutines for async calls.

Usage

Setup

To setup the ROS-Bridge connection:

val ros = Ros("localhost")
ros.connect()

Put the following Message Num.msg in src/main/ros/myrospackage/msg. Make sure your custom message type is registered to your ROS-Core/ROS-Bridge project myrosproject. See here how.

Num.msg:

int64 num

To publish 10 Num.msg messages to the topic named /num_topic

val topic = NumTopic(ros, "/num_topic")
topic.advertise()
for (i in 1..10) {
    topic.publish(i.toLong())
    delay(1000)
}

To subscribe to the topic exposed at /num_topic:

val topic = NumTopic(ros, "/num_topic")
topic.subscribe("subscriptionID") { msg, _ ->
    println("Received: ${msg.num}")
}
//delay(100_000) // don't stop execution

Call/Advertise a Service

Put the following service definition AddTwoInts.srv in src/main/ros/myrospackage/srv. Make sure your custom service type is registered to your ROS-Core/ROS-Bridge project myrosproject. See here how.

AddTwoInts.srv:

int64 a
int64 b
---
int64 sum

To call the AddTwoInts.srv service exposed at /add_two_ints_service:

val service = AddTwoInts(ros, "/add_two_ints_service")
val (sum, result) = service.call(13, 42)

To advertise and expose the AddTwoInts service at /add_two_ints_service:

val service = AddTwoInts(ros, "/add_two_ints_service")
service.advertiseService { req, id ->
    service.sendResponse(req.a + req.b, true, id)
}
//delay(100_000) // don't stop execution

Setup

The following instructions will setup your project with krosbridge.

Gradle

Add the following lines to your build.gradle.kts to 1) add the code-gen gradle plugin and the gradle kotlin serialization plugin 2) add jitpack to your dependencies repository 3) add the required and optional dependencies 4) configure the code-generation package add source set for generated sources

import com.github.thoebert.krosbridgecodegen.KROSBridgeCodegenPluginConfig

plugins {
    kotlin("plugin.serialization") version "1.7.21" // 1)
    id("io.github.thoebert.krosbridge-codegen") version "1.0.6"
}

...

repositories {
    mavenCentral()
    maven("https://jitpack.io") // 2) add line here or for android: add in settings.gradle.kts to dependencyResolutionManagement.repositories
}

dependencies { // 3)
    // Required
    implementation("com.github.thoebert:krosbridge:main-SNAPSHOT")
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.5.0")
    implementation("io.ktor:ktor-client-okhttp:2.2.4")

    // Optional for logging: 
    implementation("org.apache.logging.log4j:log4j-core:2.17.1")
    implementation("org.apache.logging.log4j:log4j-slf4j-impl:2.17.1")
    ...
}

...

configure<KROSBridgeCodegenPluginConfig> { // 4)
    packageName.set("com.company.project.messages") // package for generated data classes
}

...

// only for kotlin
kotlin.sourceSets {
    named("main"){
        kotlin.srcDir("build/generated/source/ros")
    }
}
// only on android
android.sourceSets {
    named("main") {
        java.srcDirs(File(buildDir, "generated/source/ros"))
    }
}

Build

Run the generateROSSources gradle task to generate all messages/services in the folder /build/generated/source/ros/com/company/project/messages/myrospackage/

./gradlew generateROSSources

Import them using:

import com.company.project.messages.myrospackage.Num
import com.company.project.messages.myrospackage.NumTopic
import com.company.project.messages.myrospackage.AddTwoInts

Debugging

To see debug messages, set the minimum log level to debug for the package com.github.thoebert.krosbridge. Use any SLF4J-Logging facade implementation, e.g. log4j. See here.