Hi, > There is test/test-profile and test/test-hfp in BlueZ source code. Thank you very much. Without a table of contents, it's hard to find the appropriate scripts. (This is also true for the files in folder doc.) With the test-profile code, I could register a service, and I could discover it from another device. However, a connection couldn't build up. The function NewConnection didn't call at all. (By the way, I didn't find any line of code to receive the data, how is it possible?) I monitored the connection-attempt with bluetoothctl (every row starts with the prefix "[chg] Device {address of the other device}"): ServiceResolved: yes Paired: yes (There was a little pause here.) ServiceResolved: no Paired: no Connected: no Have you got any idea what the problem is? Thank you for your help. Regards, Kristóf Horváth