Method for enabling login and establishing session for wireless communication terminal

1. A method for enabling a login in a service server for providing at least one service to a user, the method comprising:

permitting a login of a first client if the first client requests the login to the service server using user authentication information;

forcing the first client to log out from the service server if a second client logs in to the service server using the user authentication information;

sending access information of the second client to the first client so that the first client can monitor whether the second client is logged out from the service server; and

enabling a re-login of the first client if the second client is logged out from the service server, so as to allow the first client to automatically re-log in to the service server using the user authentication information.

2. The method of claim 1 , wherein the access information of the second client includes session identification information (session ID), which is created on the basis of a Session Initiation Protocol (SIP).

3. The method of claim 1 , further comprising:

when the second client logs in to the service server, sending login list/state information of pre-registered clients to the service server.

4. The method of claim 1 , wherein the service server provides an instant messenger service.

5. The method of claim 4 , wherein the user authentication information includes a user name and a password of the user.

6. The method of claim 1 , wherein the service server sends the logout information through a SMS message or an e-mail.

7. The method of claim 1 , wherein each of the first and second clients is a personal computer, a handheld computer, a computer notebook, or a mobile terminal.

8. A method for establishing a session in a service server, the method comprising:

establishing a first session with a first client if the first client logs in to the service server using user authentication information;

terminating the first session with the first client if a second client logs in to the service server using the user authentication information; and

automatically establishing a second session with the first client using the user authentication information if the second client is logged out from the service server.

9. The method of claim 8 , wherein the first session with the first client is established by enabling session identification information (session ID) created based on a Session Initiation Protocol (SIP) to be assigned to the first client in order to maintain a connection between the service server and the first client.

10. The method of claim 8 , further comprising:

prior to the establishing the second session step, storing the user authentication information in order to establish the second session with the first client.

11. A method for logging in to a service server in a mobile terminal, the method comprising:

logging in to the service server using authentication information;

being forced logout from the service server if another device logs in to the service server using the user authentication information;

receiving login state information of the another device;

determining whether the another device is logged out from the service server based on the login state information; and

automatically logging in to the service server using the user authentication information if the another device is logged out from the service server.

12. The method of claim 11 , where the login state information includes session identification information (session ID) to be assigned to the other device, which is created on the basis of a Session Initiation Protocol (SIP).

13. The method of claim 12 , where the login state information is received from the service server.

14. The method of claim 11 , where the login state information is received from the other device through LAN equipment.

15. The method of claim 14 , where the LAN equipment is one of a WLAN and a BLUETOOTH.