A method performed by a discovery server system for discovery of one or more devices of a group of devices (4A-4D) to establish a direct connection between at least two devices of the group of devices over a wide area network, the wide area network containing or being connected to the discovery server system, the discovery server system being configured for determining a group associated with the group of devices wherein each of the devices has a corresponding device identifier associated with the group, the method comprising the steps of: - receiving a discovery message from a first device of the group of devices, the discovery message comprising a device identifier associated with the first device and discovery information; - determining (S3, S32) a group associated with the first device on the basis of the received device identifier of the first device; - determining (S3, S33) the corresponding device identifier of one or more devices of the group of devices on the basis of the determined group; wherein at least a portion of the device identifier is indicative of an operator domain of the device; wherein at least one device of the determined group of devices has a destination address in an operator domain different from the operator domain of the first device; - determining (S3, S34) a corresponding destination address for each of the one or more devices associated with the determined corresponding device identifiers for the one or more devices of the determined group of devices in the operator domain of the first device; - transmitting the discovery information only to said one or more devices of the determined group of devices in the operator domain of the first device using the determined one or more corresponding destination addresses; and - exchanging the discovery information for said at least one device with a server associated with the operator domain indicated by the portion of the device identifier of said at least one device. - receiving a discovery message from a first device of the group of devices, the discovery message comprising a device identifier associated with the first device and discovery information; - determining (S3, S32) a group associated with the first device on the basis of the received device identifier of the first device; - determining (S3, S33) the corresponding device identifier of one or more devices of the group of devices on the basis of the determined group; wherein at least a portion of the device identifier is indicative of an operator domain of the device; wherein at least one device of the determined group of devices has a destination address in an operator domain different from the operator domain of the first device; - determining (S3, S34) a corresponding destination address for each of the one or more devices associated with the determined corresponding device identifiers for the one or more devices of the determined group of devices in the operator domain of the first device; - transmitting the discovery information only to said one or more devices of the determined group of devices in the operator domain of the first device using the determined one or more corresponding destination addresses; and - exchanging the discovery information for said at least one device with a server associated with the operator domain indicated by the portion of the device identifier of said at least one device.