JVM info: Oracle Corporation – 1.8.0_51 – 25.51-b03
java.net.preferIPv4Stack=true
Found java version 1.8.0_51
Added Lets Encrypt root certificates as additional trust
Target Directory: .
Data kindly mirrored by CreeperHost at https://www.creeperhost.net/
Extracting main jar:
Extracted successfully
Considering minecraft server jar

javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.ssl.Alerts.getSSLException(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
    at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
    at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
    at sun.security.ssl.ClientHandshaker.serverCertificate(Unknown Source)
    at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
    at sun.security.ssl.Handshaker.processLoop(Unknown Source)
    at sun.security.ssl.Handshaker.process_record(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
    at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
    at sun.net.www.protocol.https.HttpsClient.afterConnect(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 java.net.HttpURLConnection.getResponseCode(Unknown Source)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(Unknown Source)
    at net.minecraftforge.installer.DownloadUtils.getConnection(DownloadUtils.java:243)
    at net.minecraftforge.installer.DownloadUtils.downloadManifest(DownloadUtils.java:307)
    at net.minecraftforge.installer.json.Util.getVanillaVersion(Util.java:73)
    at net.minecraftforge.installer.actions.ServerInstall.run(ServerInstall.java:86)
    at net.minecraftforge.installer.SimpleInstaller.main(SimpleInstaller.java:128)
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.validator.PKIXValidator.doBuild(Unknown Source)
    at sun.security.validator.PKIXValidator.engineValidate(Unknown Source)
    at sun.security.validator.Validator.validate(Unknown Source)
    at sun.security.ssl.X509TrustManagerImpl.validate(Unknown Source)
    at sun.security.ssl.X509TrustManagerImpl.checkTrusted(Unknown Source)
    at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(Unknown Source)
    ... 19 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.provider.certpath.SunCertPathBuilder.build(Unknown Source)
    at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(Unknown Source)
    at java.security.cert.CertPathBuilder.build(Unknown Source)
    ... 25 more

Failed to download version manifest, can not find server jar URL.
There was an error during installation

/* I already tried adding creeperhosts certificates to java’s cacert. keep in mind I don’t have any experience with this thing…. :DDDDD So I can only follow your instuctions. */