A method for establishing a communication session, the method comprises: establishing a chat session, by a chat server, between a first terminal device and a second terminal device, characterized in that the method further comprises: determining, by the chat server, if both the first terminal device and the second terminal device support a Web Real-Time Communications, WebRTC, service, forwarding, by the chat server, an invitation from at least one of the following: the first terminal device, the second terminal device to the other of the following: the first terminal device, the second terminal device to initiate communication over the Web Real-Time Communications, WebRTC, service, in response to a detection that the other of the following: the first terminal device, the second terminal device accepts the invitation requesting, by the chat server, from a communication server an initiation of a communication channel implemented with the Web Real-Time Communications, WebRTC, service, in response to an establishment of the communication channel implemented with the Web Real-Time Communications, WebRTC, service establishing the communication session for communicating at least over the Web Real-Time Communications, WebRTC, service, and providing, by the chat server, a network link to the established communication session to the first terminal device and the second terminal device, the network link is generated during the initiation of the communication channel. establishing a chat session, by a chat server, between a first terminal device and a second terminal device, characterized in that the method further comprises: determining, by the chat server, if both the first terminal device and the second terminal device support a Web Real-Time Communications, WebRTC, service, forwarding, by the chat server, an invitation from at least one of the following: the first terminal device, the second terminal device to the other of the following: the first terminal device, the second terminal device to initiate communication over the Web Real-Time Communications, WebRTC, service, in response to a detection that the other of the following: the first terminal device, the second terminal device accepts the invitation requesting, by the chat server, from a communication server an initiation of a communication channel implemented with the Web Real-Time Communications, WebRTC, service, in response to an establishment of the communication channel implemented with the Web Real-Time Communications, WebRTC, service establishing the communication session for communicating at least over the Web Real-Time Communications, WebRTC, service, and providing, by the chat server, a network link to the established communication session to the first terminal device and the second terminal device, the network link is generated during the initiation of the communication channel. determining, by the chat server, if both the first terminal device and the second terminal device support a Web Real-Time Communications, WebRTC, service, forwarding, by the chat server, an invitation from at least one of the following: the first terminal device, the second terminal device to the other of the following: the first terminal device, the second terminal device to initiate communication over the Web Real-Time Communications, WebRTC, service, in response to a detection that the other of the following: the first terminal device, the second terminal device accepts the invitation requesting, by the chat server, from a communication server an initiation of a communication channel implemented with the Web Real-Time Communications, WebRTC, service, in response to an establishment of the communication channel implemented with the Web Real-Time Communications, WebRTC, service establishing the communication session for communicating at least over the Web Real-Time Communications, WebRTC, service, and providing, by the chat server, a network link to the established communication session to the first terminal device and the second terminal device, the network link is generated during the initiation of the communication channel.