Hello there!
Me and my friends decided to move to the version 1.10.2 for playing modded Minecraft. We have a Forge server hosted on a polish hosting site (craftserve.pl). Everything worked fine on 1.7.10 - even with a huge modpacks all of us were able to join and play together. But, I finally decided to update to 1.10.2. There goes my problem: I installed Forge (12.18.3.2185) on the server and while my client was still vanilla I was able to join the server - no problem. But when I finally installed Forge on my client, suddenly I'm no longer capable of connecting to the server. It shows just "Can't connect to server" in the server list and when I'm trying to connect it gives me the "Internal Exception: java.io.IOException: An existing connection was forcibly closed by remote host" text. That seems pretty weird for me.
Client log: http://pastebin.com/YHwivQYP (if you wonder what this weird russian text after "IOException" means, it's basically "an existing connection was forcibly closed by remote host" in polish)
Server log: http://pastebin.com/UXEnVqsb