The server ignores the server-port option specified in server.properties and always starts on port 25565. Using --port as a command line argument works.
Environment
Linux 64 bits
java version "1.8.0_181"
Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)
Can confirm.