Server raises exception and closes immediately

Won't let me attach log file so here's the relevant section:

[23:08:29] [Server thread/WARN]: **** FAILED TO BIND TO PORT![23:08:29] [Server thread/WARN]: **** FAILED TO BIND TO PORT![23:08:29] [Server thread/WARN]: The exception was: io.netty.channel.unix.Errors$NativeIoException: bind(..) failed: Cannot assign requested address[23:08:29] [Server thread/WARN]: Perhaps a server is already running on that port?[23:08:29] [Server thread/INFO]: Stopping server[23:08:29] [Server thread/INFO]: Saving worlds[23:08:29] [Server thread/ERROR]: Exception stopping the serverjava.lang.NullPointerException: null at net.minecraft.server.MinecraftServer.a(SourceFile:574) ~[server.jar:?] at net.minecraft.server.MinecraftServer.s(SourceFile:601) ~[server.jar:?] at yd.s(SourceFile:556) ~[server.jar:?] at net.minecraft.server.MinecraftServer.v(SourceFile:709) ~[server.jar:?] at net.minecraft.server.MinecraftServer.a(SourceFile:256) ~[server.jar:?] at java.lang.Thread.run(Thread.java:832) [?:?]

There is nothing occupying the port. I have tried deleting and re-downloading the server. I have tried turning the PC on and off again.