Specify the required host IP in the port mapping
docker run -p 127.0.0.1:1234:80 -d -v /var/www/:/usr/share/nginx/html nginx:1.9
If you are doing a reverse proxy, you might want to put them all on a user defined network along with your reverse proxy, then everything is in a container and accessible on their internal network.
docker network create net
docker run -d --net=web -v /var/www/:/usr/share/nginx/html nginx:1.9
docker run -d -p 80:80 --net=web haproxy