Abstract: A method is provided of using the Host Identity Protocol, HIP, to establish a connection between a second host (32) and an application socket (42) on a first host (30), comprising establishing a new or selecting an existing HIP Security Association (46) between the first and second hosts (30, 32), creating a new or selecting an existing Tube Association (44), identified by a Tube Identifier, between the application socket (42) and the Security Association (46), forming an association (43, 45) for the connection between the application socket (42), the Security Association (46) and the Tube Association (44), thereby establishing a connection between the second host (32) and the application socket (42) on the first host (30) through the Security Association (46) and Tube Association (44).