You may also see this errors before and frustrating how to fix this.

Response message: Error opening socket: 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

The idea is that you have to add the certificate to your java trusted store.

navigate to /bin in jmeter folder
edit system.properties and put in the location of your keystore.

# SSL properties (moved from jmeter.properties)
# Location of the truststore (trusted certificates)
javax.net.ssl.trustStore=/home/kz/jssecacerts

But how can I get the jssecacerts (Keystore) ?

There’s a nifty tool from SUN (Oracle) called InstallCert, get it from here, with this tool you can install any certification from any website you want.
to install a certification or you could use the keytool to import the certificate (in der format)

“java InstallCert example.com:443” or “keytool -import -file xxx.cer”

and hit enter.  InstallCert will generate keystore for you, that is, no more error

ps. with keytool the output file is located in a different name and folder.