Why would anyone SYN flood my HA?

I am seeing a lot of SYN_RECV on the HA port. I know the internet is a hostile place, but why would anyone send SYN requests to this port? I am seeing a ton of different spoofed addresses. Sometimes with messages in it from the other party, or obscene stuff.

I have it out there mainly for the Samsung ST integration. I am rethinking this.