How to send http request from Docker to localhost or Virtual Machine
By default, Docker creates a virtual interface (docker0) in your host machine with IP 172.17.42.1. Each of the container launched will have an IP of the network 172.17.42.1/16, and they will be able to connect to host machine connecting to IP 172.17.42.1.
If you want to connect a docker container with another service running in a virtual machine running with other provider (e.g.: virtualbox, vmware), the easiest way is forwarding the ports needed by the service to you host machine and then, from your docker container, connecting to IP 172.17.42.1. You should check your virtual machine provider documentation to see details about this. And if you are using libvirt/KVM (or with any other provider), you can use iptables to enable port forwarding.