Hi, Shelton I have checked the Hadoop version, and it is indeed using protobuf version 2.5.0, while the protobuf version for Spark could not be found. The versions of Hadoop and Spark are 3.4.0 and 3.5.3, respectively. I also checked the client using Java 11 to connect to the Spark master, which is running on Java 8. I'm not sure if the difference in Java versions between the client and the master affects the connection. Thank you for your response; it has enlightened me in many ways. ... View more