Port already used but it isn't

Hi i'm getting this error

06.07 19:13:39 [Server] INFO Server returned HTTP response code: 502 for URL: http://mcstats.org/report/BungeeCord
06.07 15:33:38 [Server] INFO at java.lang.Thread.run(Unknown Source)
06.07 15:33:38 [Server] INFO at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:101)
06.07 15:33:38 [Server] INFO at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:365)
06.07 15:33:38 [Server] INFO at...

Port already used but it isn't