Android Studio – build android apps through command-line using gradle

I have rather a curiosity than a problem which in its very own place could lead to a problem if not solved;

I’ve found out for building an android app you can invoke gradlew(.bat) at root dir of a project. so when I ran for instance
gradlew tasks
it generates the followings

Downloading https://services.gradle.org/distributions/gradle-4.1-all.zip

Exception in thread "main" java.net.UnknownHostException: services.gradle.org
        at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
        at java.net.PlainSocketImpl.connect(Unknown Source)
        at java.net.SocksSocketImpl.connect(Unknown Source)
        at java.net.Socket.connect(Unknown Source)
        at sun.security.ssl.SSLSocketImpl.connect(Unknown Source)
        at sun.security.ssl.BaseSSLSocketImpl.connect(Unknown Source)
        at sun.net.NetworkClient.doConnect(Unknown Source)
        at sun.net.www.http.HttpClient.openServer(Unknown Source)
        at sun.net.www.http.HttpClient.openServer(Unknown Source)
        at sun.net.www.protocol.https.HttpsClient.<init>(Unknown Source)
        at sun.net.www.protocol.https.HttpsClient.New(Unknown Source)
        at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(Unknown Source)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
        at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
        at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
        at org.gradle.wrapper.Download.downloadInternal(Download.java:58)
        at org.gradle.wrapper.Download.download(Download.java:44)
        at org.gradle.wrapper.Install$1.call(Install.java:61)
        at org.gradle.wrapper.Install$1.call(Install.java:48)
        at org.gradle.wrapper.ExclusiveFileAccessManager.access(ExclusiveFileAccessManager.java:65)
        at org.gradle.wrapper.Install.createDist(Install.java:48)
        at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:128)
        at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:61)

I simply can connect to internet and let it to download the necessary file,
But here my mentioned curiosity originates:
How it comes that when I build(debug) the app through android studio, android studio generates the APK with no error at all?
In android studio I defined ‘local gradle distribution’ to be used instead of ‘default gradle wrapper’ as appeared in the link below:

captured_and_std_img

Back to command-line, Afterwards I defined the environment variable GRADLE_HOME and tried one more time to build the app using gradle which is now a recognized command, as following:

gradle assembleDebug

But it also produced the followings:

Starting a Gradle Daemon, 2 incompatible Daemons could not be reused, use --status for details

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring root project 'MyApplication2'.
> Could not resolve all files for configuration ':classpath'.
   > Could not resolve com.android.tools.build:gradle:3.0.1.
     Required by:
         project :
      > Could not resolve com.android.tools.build:gradle:3.0.1.
         > Could not get resource 'https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.0.1/gradle-3.0.1.pom
'.
            > Could not GET 'https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.0.1/gradle-3.0.1.pom'.
               > dl.google.com
      > Could not resolve com.android.tools.build:gradle:3.0.1.
         > Could not get resource 'https://jcenter.bintray.com/com/android/tools/build/gradle/3.0.1/gradle-3.0.1.pom'.
            > Could not GET 'https://jcenter.bintray.com/com/android/tools/build/gradle/3.0.1/gradle-3.0.1.pom'.
               > jcenter.bintray.com

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

* Get more help at https://help.gradle.org

BUILD FAILED in 38s

I’m not sure if assembleDebug could be used as a parameter with gradle command, I know you could use it with gradlew, but I still don’t want to download the file (gradle-4.1-all.zip) and want to build the APK using ‘local gradle distribution’. :))
Any possible solution would be appreciated

EDIT:
build.gradle(project) file contents:

//task wrapper(type: Wrapper) {
//  gradleVersion = '4.1'
//}

buildscript {
    
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.1'
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

build.gradle(module):

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    defaultConfig {
        applicationId "com.example.myapplication"
        minSdkVersion 18
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    productFlavors {
    }
    buildToolsVersion '28.0.3'
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:25.3.1'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    implementation 'com.android.support:design:25.3.1'
}