yshurik/stunnel is a container utility for making secure tunnels between docker hosts. As data flow could be not protected between docker hosts located in separate locations the container can work well as a transport layer.
docker host1 docker host2
+------------+ +---------------+ +----------------+ +-------------+
|container | |yshurik/stunnel| |yshurik/stunnel | |container |
|with service|--|with -s to make|..internet..|a client to make|--|with a client|
|to protect | |secure tunnel | |endpoint to use | |of host1 |
+------------+ +---------------+ +----------------+ +-------------+
docker run [DOCKER_OPTIONS] yshurik/stunnel -c <connect-port> [-s]
-c- Required; to connect to, in the form :.-s- Optional; specifies that the endoint is a server.