| Vladimir Chtchetkine | d86c724 | 2011-12-09 15:45:46 -0800 | [diff] [blame] | 1 | ADB COMMUNICATION OVER QEMUD SERVICE |
| 2 | |
| 3 | I. Overview: |
| 4 | ------------ |
| 5 | |
| 6 | In certain cases ADB communication over TCP port forwarding might be unreliable. |
| 7 | For instance, connection manager in the guest system may decide to reset all |
| 8 | network connections, in which case connection between the ADB host, and ADB |
| 9 | daemon running in the guest will be broken, and will not be reestablish until ADB |
| 10 | host is killed, and then restarted. To address this issue ADB communication has |
| 11 | been moved to use QEMUD pipe to transfer data between the emulator, and the |
| 12 | ADB daemon running in the guest. |
| 13 | |
| 14 | |
| 15 | II. Implementation: |
| 16 | ------------------- |
| 17 | |
| 18 | There are two major components implemented in the emulator to support ADB |
| 19 | communication over QEMUD pipe: |
| 20 | |
| 21 | 1. ADB server. |
| 22 | 2. ADB QEMUD service (or ADB client). |
| 23 | |
| 24 | ADB server is implemented as a socket server that is bound to the ADB port (which |
| 25 | is the 'base port' + 1), and is responsible for accepting connections coming from |
| 26 | the ADB host, and associatiating accepted connections with an ADB client. |
| 27 | |
| 28 | ADB client is implemented as QEMUD service (named 'adb'), and is responsible for |
| 29 | accepting connections coming from the ADB daemon running in the guest, and |
| 30 | associating accepted connections with ADB server. |
| 31 | |
| 32 | Essentially, ADB server, and ADB client serve as a bridge between ADB running on |
| 33 | the host, and ADB running on the guest: ADB server receives data from ADB host, |
| 34 | and channels them through ADB client to the ADB guest. Likewise, ADB client |
| 35 | receives data from the ADB guest, and channels them through ADB server to the ADB |
| 36 | host. The only tricky part here is establishing the connection. Once connection |
| 37 | is established, everything is straight forward. |
| 38 | |
| 39 | II.III Establishing the connection: |
| 40 | ----------------------------------- |
| 41 | |
| 42 | The connection between ADB host and ADB guest is considered to be established, |
| 43 | when there is an association between ADB socket connection in the ADB server, and |
| 44 | QEMUD pipe connection in the ADB client, and ADB guest is ready to receive data |
| 45 | from the ADB host. |
| 46 | |
| 47 | Since there is no particular order, in which ADB server, and ADB client |
| 48 | connections are made, ADB server runs a list of pending host and guest |
| 49 | connections. Every time either connection is made, that connection goes into a |
| 50 | pending list on condition that there is no pending connection on the other side. |
| 51 | If, however, there is already a pending connection from the other side, that |
| 52 | pending connection is removed from the pending list, and gets associated with the |
| 53 | new connection. |