java.net.UnknownHostException: github.com when being offline

[hendrikebbers]

If the plugin wants to download a specific solc version and the pc is offline an exception is thrown. While it makes sense to show an error if the needed solc version can not be downloaded it makes sense to have a more detailed information than saying that github.com is not reachable. Next to this the error even happens if a useable version is installed locally but a newer version is defined in the releases.json.

I would like to work on that issue. Please assign me.

The error message:

Could not compile Solidity files
java.net.UnknownHostException: github.com
	at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:567)
	at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:327)
	at java.base/java.net.Socket.connect(Socket.java:633)
	at java.base/sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:304)
	at java.base/sun.security.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:174)
	at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:183)
	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:531)
	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:636)
	at java.base/sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:266)
	at java.base/sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:380)
	at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:193)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1242)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1128)
	at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:179)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1665)
	at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1589)
	at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:224)
	at java.base/java.net.URL.openStream(URL.java:1161)
	at kotlin.io.TextStreamsKt.readBytes(ReadWrite.kt:150)
	at org.web3j.sokt.SolcInstance.install(SolcInstance.kt:72)
	at org.web3j.mavenplugin.solidity.SolidityCompiler.getSolcProcessFromSokt(SolidityCompiler.java:78)
	at org.web3j.mavenplugin.solidity.SolidityCompiler.compileSrc(SolidityCompiler.java:51)
	at org.web3j.mavenplugin.JavaClassGeneratorMojo.parseSoliditySources(JavaClassGeneratorMojo.java:301)
	at org.web3j.mavenplugin.JavaClassGeneratorMojo.processSolidityFile(JavaClassGeneratorMojo.java:171)
	at org.web3j.mavenplugin.JavaClassGeneratorMojo.processSolidityFiles(JavaClassGeneratorMojo.java:229)
	at org.web3j.mavenplugin.JavaClassGeneratorMojo.execute(JavaClassGeneratorMojo.java:213)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:137)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:210)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:156)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:148)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:117)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:81)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:56)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:305)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:192)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:105)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:957)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:289)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:193)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:282)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:225)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:406)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:347)
	at org.codehaus.classworlds.Launcher.main(Launcher.java:47)