1. A method performed by a communication server comprising:receiving a request from a first network entity to set up a communication session between a first user at a first device and a second user at a second device, wherein the first network entity is registered with the communication server;
in response to the request, generating a token, wherein the token is configured to grant access to the communication session;
sending the token to the first network entity;
after sending the token to the first network entity, receiving the token from the first user at the first device; and
causing the communication session to be set up between the first user at the first device and the second user at the second device according to the token, wherein a destination address of the second device is kept secret from the first user.