Ubuntu14.04 on fig appears couldn ' t connect to Docker daemon ... Problem

After the Docker and fig are properly installed on the Ubuntu14.04, Docker can be used normally, but the following error occurs when using Fig

Couldn ' t connect to Docker daemon at Http+unix://var/run/docker.sock-is it running?
 
If it ' s at a non-standard location, specify the URL with the DOCKER_HOST environment variable.

1. Edit/etc/default/docker.io file and join

docker_opts= "-H tcp://127.0.0.1:4243-h unix:///var/run/docker.sock"

2. Restart Docker Service

sudo service Docker.io restart

3. Check and make sure Docker runs in localhost:4243

$ netstat-ant  |grep 4243
tcp        0      0 127.0.0.1:4243          0.0.0.0:*               LISTEN

4. Set the DOCKER_HOST environment variable that can be added to the ~/.BASHRC file

Export docker_host=tcp://localhost:4243

5. Run again to start the error of the Fig command, the problem disappears.