HDFS-599 introduced a new service port on NameNode to separate system traffic (e.g., heartbeats/blockreports) from client file access requests so that they can be prioritized. All Datanode traffic now goes to the service port. However, datanode also serves as a proxy for HFTP requests from client (served by StreamFile servlet). These HFTP traffic should continue to use the client port on NameNode. Moreover, using the service port for HFTP is incompatible with the existing way of selecting delegation tokens.