1. A method in an Internet Protocol (IP) Multimedia Subsystem Gateway for enabling a legacy host, attached to a local network, to discover a service provided by a remote server, comprising the steps of: subscribing to an IP Multimedia Subsystem presence service; receiving presence information published by said IP Multimedia Subsystem presence service, said presence information including at least one Globally Routable User agent Uniform Resource Identifier (URI) and a service description associated therewith; receiving a service discovery message sent by said legacy host, wherein said service discovery message is broadcast in said local network according to a service discovery protocol; searching said presence information including said service description to identify a requested service and an associated Globally Routable User agent URI; and sending a response to said legacy host including a local network address of said Gateway, whilst maintaining a mapping between said local network address expressed in a legacy protocol and said Globally Routable User agent URI expressed in an IP Multimedia Subsystem protocol.