Play-App Suspicious Logs

Question

I have a Play!+Scala app using Play-2.4. Looking at the server logs, I see unrelated connection logs and exceptions. For example:

2017-11-06 21:36:45,174 ERROR [New I/O worker #1] application [?:?]

    ! @76020798a - Internal server error, for (CONNECT) [pl.metin2.gameforge.com:443] ->

    play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[NullPointerException: null]]
            at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:265) ~[com.typesafe.play.play_2.11-2.4.6.jar:2.4.6]

I am not connecting with gameforge at all, but there is still this message. Similarly this one:

! @75fjch9ik - Internal server error, for (OPTIONS) [sip:nm] ->

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[NullPointerException: null]]
        at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:265) ~[com.typesafe.play.play_2.11-2.4.6.jar:2.4.6]
            at org.jboss.netty.handler.codec.http.HttpRequestDecoder.createMessage(HttpRequestDecoder.java:75) ~[io.netty.netty-3

It seems to me that this New I/O worker threadpool gets created by netty. Any kind soul has any idea, what might be causing these connections? Server is hosted on AWS EC2.