I'm not sure if you guys are still listening on this closed bug but I think I've found another issue ;) I'm using python 3.5.1 + asyncio 3.4.3 with the latest aiobotocore (which uses aiohttp 0.21.0) and had two sessions (two TCPConnectors), one doing a multitude of GetObjects via HTTP1.1, and the other doing PutObject, and the PutObject session returns error 61 (connection refused) from the same _sock_connect_cb. It feels like a similar issue to the original. I'll see if I can get small testcase.