TAILIEUCHUNG - Communication Systems for the Mobile Information Society phần 10

Đối với các điểm nóng thương mại, như trong các khách sạn, tuy nhiên, thanh toán là một nhiệm vụ cần thiết. Do thiếu các tiêu chuẩn và số lượng lớn các nhà khai thác điểm nóng, một số các phương pháp thanh toán khác nhau đang xuất hiện trên thị trường. | Bluetooth 323 The Service Discovery Protocol Theoretically it would be possible to begin the transfer of user data between two devices right after establishing an ACL and L2CAP connection. Bluetooth however can be used for many different applications and many devices thus offer several different services to remote devices at the same time. A mobile phone for example offers services like wireless Internet connections dial-up network file transfers to and from the local file system exchange of addresses and calendar entries etc. In order for a device to detect which services are offered by a remote device and how they can be accessed each Bluetooth device contains a service database that can be queried by other devices. The service database is accessed via the L2CAP PSM 0x0001 and the protocol to exchange information with the database is called the service discovery protocol SDP . The database query can be skipped if a device already knows how a remote service can be accessed. As Bluetooth is very flexible it offers services the option to change their connection parameters at runtime. One of those connection parameters is the RFCOMM channel number. More on this topic can be found in Section . On the application layer services are also called profiles. The headset service headset profile ensures that a headset interoperates with all Bluetooth-enabled mobile phones that also support the headset profile. More about Bluetooth profiles can be found in Section . Each Bluetooth service has its own universally unique ID UUID with which it can be identified in the SDP database. The dial-up server service for example has been assigned UUID 0x1103. In order for the Bluetooth stack of a PC to be able to connect to this service on a remote device like a mobile phone the SDP database is queried at connection establishment and the required settings for the service are retrieved. For the dial-up server service the database returns information to the requesting device .

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