Cannot bind to port

I have problem with starting my server. It fails to connect my port (25565) to server. What shall I do?

[10:48:21] [Worker-Main-5/INFO]: Loaded 7 recipes
[10:48:21] [Worker-Main-5/INFO]: Loaded 927 advancements
[10:48:22] [Server thread/INFO]: Starting minecraft server version 1.16.3
[10:48:22] [Server thread/INFO]: Loading properties
[10:48:22] [Server thread/INFO]: Default game type: SURVIVAL
[10:48:22] [Server thread/INFO]: Generating keypair
[10:48:22] [Server thread/INFO]: Starting Minecraft server on
[10:48:22] [Server thread/INFO]: Using epoll channel type
[10:48:22] [Server thread/WARN]: **** FAILED TO BIND TO PORT!
[10:48:22] [Server thread/WARN]: The exception was:$NativeIoException: bind(…) failed: Address already in use
[10:48:22] [Server thread/WARN]: Perhaps a server is already running on that port?
[10:48:22] [Server thread/INFO]: Stopping server
[10:48:22] [Server thread/INFO]: Saving worlds
[10:48:22] [Server thread/ERROR]: Exception stopping the server
java.lang.NullPointerException: null
at net.minecraft.server.MinecraftServer.a(SourceFile:569) ~inecraft_server.1.16.3.jar:?]
at net.minecraft.server.MinecraftServer.t(SourceFile:596) ~inecraft_server.1.16.3.jar:?]
at zg.t(SourceFile:558) ~inecraft_server.1.16.3.jar:?]
at net.minecraft.server.MinecraftServer.w(SourceFile:704) ~inecraft_server.1.16.3.jar:?]
at net.minecraft.server.MinecraftServer.a(SourceFile:254) ~inecraft_server.1.16.3.jar:?]
at [?:1.8.0_275]

When I change port to 25566 it starts, but on ip: What am I doing wrong?

[10:54:43] [Server thread/INFO]: Time elapsed: 13233 ms
[10:54:43] [Server thread/INFO]: Done (16.525s)! For help, type “help”
[10:54:43] [Server thread/INFO]: Starting GS4 status listener
[10:54:43] [Server thread/INFO]: Thread Query Listener started
[10:54:43] [Query Listener #1/INFO]: Query running on

You likely have another minecraft server running, somewhere, somehow.

Easiest answer by far is to simply reboot your server.