A method for establishing a communication session, the method comprising: receiving, by a server, a request for establishing a communication session from a first web real-time communication, WebRTC, device to a second web real-time communication, WebRTC, device, acknowledging, by the server, the request to the first WebRTC device, and in response to a receipt of the acknowledging: generating, by the first WebRTC device, a first connection request for a voice call, the first connection request comprising at least a network address of the first WebRTC device towards a WebRTC gateway device for establishing a first connection for voice call to the second WebRTC device, the WebRTC gateway device configured to transfer the first connection request to a public switched telephone network, generating, by the first WebRTC device, a second connection request comprising an identifier representing the first WebRTC device towards a connection management server implementing WebRTC based communication, and in response to an establishment of the first connection for the voice call by the second WebRTC device: generating an inquiry to the connection management server by the second WebRTC device for determining if a connection request is received from the first WebRTC device with which the first connection for the voice call is established by the second WebRTC device, the inquiry to the connection management server carrying an identifier representing the first WebRTC device from which the first connection for the voice call is established, and in response to a determination, by the second WebRTC device, that the connection management server stores an indication on the connection request from the first WebRTC device establishing a communication session between the first WebRTC device and the second WebRTC device, the communication session comprising both the first connection for the voice call and a second connection. receiving, by a server, a request for establishing a communication session from a first web real-time communication, WebRTC, device to a second web real-time communication, WebRTC, device, acknowledging, by the server, the request to the first WebRTC device, and in response to a receipt of the acknowledging: generating, by the first WebRTC device, a first connection request for a voice call, the first connection request comprising at least a network address of the first WebRTC device towards a WebRTC gateway device for establishing a first connection for voice call to the second WebRTC device, the WebRTC gateway device configured to transfer the first connection request to a public switched telephone network, generating, by the first WebRTC device, a second connection request comprising an identifier representing the first WebRTC device towards a connection management server implementing WebRTC based communication, generating, by the first WebRTC device, a first connection request for a voice call, the first connection request comprising at least a network address of the first WebRTC device towards a WebRTC gateway device for establishing a first connection for voice call to the second WebRTC device, the WebRTC gateway device configured to transfer the first connection request to a public switched telephone network, generating, by the first WebRTC device, a second connection request comprising an identifier representing the first WebRTC device towards a connection management server implementing WebRTC based communication, and in response to an establishment of the first connection for the voice call by the second WebRTC device: generating an inquiry to the connection management server by the second WebRTC device for determining if a connection request is received from the first WebRTC device with which the first connection for the voice call is established by the second WebRTC device, the inquiry to the connection management server carrying an identifier representing the first WebRTC device from which the first connection for the voice call is established, and in response to a determination, by the second WebRTC device, that the connection management server stores an indication on the connection request from the first WebRTC device establishing a communication session between the first WebRTC device and the second WebRTC device, the communication session comprising both the first connection for the voice call and a second connection. generating an inquiry to the connection management server by the second WebRTC device for determining if a connection request is received from the first WebRTC device with which the first connection for the voice call is established by the second WebRTC device, the inquiry to the connection management server carrying an identifier representing the first WebRTC device from which the first connection for the voice call is established, and in response to a determination, by the second WebRTC device, that the connection management server stores an indication on the connection request from the first WebRTC device establishing a communication session between the first WebRTC device and the second WebRTC device, the communication session comprising both the first connection for the voice call and a second connection.