A roaming method for maintaining connectivity between a client and a server through heterogeneous wireless networks includes the steps of establishing an initial connection between the client and the server through a first selected one of the heterogeneous wireless networks, detecting disconnection of the initial connection, and establishing a current connection between the client and server through a second selected one of the heterogeneous wireless networks upon detecting that the initial connection has been disconnected. A system, which includes the client and the server, for realizing the roaming method is also disclosed.