The document discusses the Android Debug Bridge (ADB) and how it works. It provides an overview of ADB including the three main components: ADB clients, server, and daemon (adbd). It also covers topics like command details, tips, advanced features and the internal workings of ADB.

1. ADB
(Android Debug Bridge):
How it works?
2012.2.13 Android Builders Summit
Tetsuyuki Kobayashi
1

2. Let's talk about inside of Android.
http://www.kmckk.co.jp/eng/kzma9/ 2
http://www.kmckk.co.jp/eng/jet_index.html

3. Who am I?
 20+ years involved in embedded systems
 10 years in real time OS, such as iTRON
 10 years in embedded Java Virtual Machine
 Now GCC, Linux, QEMU, Android, …
 Blogs
 http://d.hatena.ne.jp/embedded/ (Personal)
 http://blog.kmckk.com/ (Corporate)
 http://kobablog.wordpress.com/(English)
 Twitter
 @tetsu_koba
3

4. Today's topics
 What is ADB?
 ADB internal
 Command details & Tips
 Advanced Topics
4

5. What is ADB?
 If you are an Android builder, you have used
”adb logcat”, ”adb shell”
 Even if you only use DDMS in Eclipse, adb is
working under the hood.
 Using adb, you can connect emulator or actual
target device.
 ”adb kill-server”? what does it mean?

6. How to connect?
Host Target device
Emulator Adb clients
”adb shell”
Adbd
How to connect?
QEMU Adbd
6

7. 3 elements of ADB
 adb clients
 executable with subcommand
 ”adb shell”, ”adb logcat” : the end point of host side
 adb server
 running on host on back-ground
 act as proxy between adb clients and adbd
 adb daemon (adbd)
 running on target device
 started by init, if die, restarted by init again
7

8. ADB overview
Host Target device
Execute services on
Emulator new thread/subprocess
Adb clients
Adbd TCP port:5037
TCP
Adb server USB/TCP Adbd
QEMU
8

9. 2 roles of ADB
 Providing ”Transport”
 communication path between host and target
device
 USB or TCP: but clients don't have to aware
 Providing ”Services”
 executing something on the target devices through
the transport.
 ”adb shell” for executing command
 ”adb push/pull” for file transfer
9

10. When does adb server start?
 Explicitly, ”adb start-server”
 It starts adb server as back ground process.
 Usually it does automatically on demand. You
don't have to do ”adb start-server”.
 When you want to restart adb server, do ”adb
kill-server”
 Actually, adb clients and adb server shares
same executable
 ”adb start-server” equals ”adb fork-server server &”
10

11. Port forwarding
adb forward tcp:1234 tcp:1234
Host Target device
Transport
client socket
server socket USB or TCP port 1234
port 1234
11

12. Port forwarding (cont.)
adb forward tcp:1234 tcp:1234
example: connecting to gdbserver in the device from gdb client from host
Host Target device
gdb client
connect to
localhost:1234
Transport
client socket
server socket USB or TCP port 1234
port 1234
listen to
localhost:1234
Both gdb client and gdbserver gdbserver
do not aware of transport
12

13. ADB internal
 Source code
 How to get ADB logs
 Sequence chart
 Simple ruby script to connect adb server
 Secure mode
 Switching transport mode
13

14. Source code
 system/core/adb in Android source tree
 16,000 lines in *.[ch]
 From this directory adb and adbd are built
 Don't confuse.
 common files between adb and adbd
 adb.c, fdevent.c, transort.c, transport_local.c,
tansport_usb.c, service.c, sockets.c, util.c
#if ADB_HOST
/* code for adb*/
#else
/* code for adbd */
#endif
14

15. Source code(cont.)
 files only for adbd
 backup_service.c, file_sync_service.c,
jdwp_service.c, framebuffer_service.c,
remount_services.c, usb_linux_clients.c,
log_service.c
 files only for adb
 console.c, adb_clients.c, file_sync_client.c,
usb_vendors.c,
get_my_path_{linux,darwin,windows,freebsd}.c,
usb_{linux,macos,libusb,windows}.c
 documents
 OVERVIEW.TXT, SERVICES.TXT, protocol.txt
15

16. How to get ADB logs
 For adb clients and adb server, set environment
variable ADB_TRACE

$ adb kill-server

$ ADB_TRACE=all start-server
 For adbd, set system property
”persist.adb.trace_mask” in hexadecimal
 # set_property persist.adb.trace_mask 0xfff
 I found some trivial bugs. see below
 http://blog.kmckk.com/archives/4080002.html
16
 http://blog.kmckk.com/archives/4087230.html

17. Sequence chart
Adb client
“adb shell ls” Adb server adbd
host:version
OKAY0004001d
Check version
host:transport-any
Specify the OKAY
destination
shell:ls
[OPEN]shell:ls
Command subprocess
to adbd
[OPEN]shell:ls
OKAY
ls
[WRITE]len=247
len=247
stdout len=247
17

18. Simple ruby script to connect to
adb server
require 'socket' hostname = 'localhost'
port = 5037
def error_exit
puts "Error" s = TCPSocket.open(hostname, port)
exit 1 send_to_adb(s, "host:version")
end error_exit if ! check_version(s)
s.close
def send_to_adb(s, msg)
s.printf("%04x%s", s = TCPSocket.open(hostname, port)
msg.length, msg) send_to_adb(s, "host:transport-any")
end error_exit if ! check_okay(s)
send_to_adb(s, "shell:ls")
def check_okay(s) error_exit if ! check_okay(s)
(s.read(4) == "OKAY")
end while line = s.gets
puts line.chop
def check_version(s) end
(s.read(12) == s.close
"OKAY0004001d")
end
change ”shell:ls” as you like. 18
http://blog.kmckk.com/archives/4092210.html

19. Secure mode
 Android smart phone products have adbd.
Usually it runs on secure mode. (secure = 1)
 if secure == 1, change adbd as SHELL user(=
not privileged), else it keeps running as root
user
 In secure mode, all services invoked by adbd
ran as SHELL user. Some causes ”permission
denied”.
19

20. How secure mode decided
 Running on emulator → secure = 0
 System property ”ro.secure” == 1 → secure = 1
 if ”ro.debuggable” == 1, you can restart adb
unsecure by ”adb root”
 All Android phone products are shipped in
”ro.secure” = 1, ”ro.debuggable” = 0.
 See adb.c: adb_main
 http://blog.kmckk.com/archives/4099821.html
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21. Switching transport mode
Switching USB mode to TCP mode
$ adb shell netcfg
lo UP 127.0.0.1 255.0.0.0 0x00000049
eth0 UP 192.168.1.139 255.255.255.0 0x00001043
$ adb tcpip 5555
restarting in TCP mode port : 5555
$ adb devices
List of devices attached
$
disconnected from USB. Then restart adb server with specifying target IP address.
$ adb kill-server
$ ADBHOST=192.168.1.139 adb devices
* daemon not running. starting it now on port 5037 *
* daemon started successfully *
List of devices attached
emulator-5554 device
$
21

22. Switching transport mode (What
happen inside?)
 See service.c restart_tcp_service
 property_set(”service.adb.tcp.port”, value);
 Note: before Android 4.0, this cause
”permission denied” in secure mode and
ignored silently!
 After that, exit(1);
 init restarts adbd.
 ”service.adb.tcp.port” is checked in adb.c
adb_main
22

23. Patch to enable switching to TCP
mode in secure Android 2.3
system/core/init/property_service.c
$ diff -u property_service.c.2 property_service.c
--- property_service.c.2 2012-02-07 18:40:34.472414791
+0900
+++ property_service.c 2012-02-07 18:41:24.782801630
+0900
@@ -79,6 +79,7 @@
{ "debug.", AID_SHELL, 0 },
{ "log.", AID_SHELL, 0 },
{ "service.adb.root", AID_SHELL, 0 },
+ { "service.adb.tcp.port", AID_SHELL, 0 },
{ "persist.sys.", AID_SYSTEM, 0 },
{ "persist.service.", AID_SYSTEM, 0 },
{ "persist.security.", AID_SYSTEM, 0 },
This avoids ”permission denied” when set property ”service.adb.tcp.port”.
http://blog.kmckk.com/archives/4098873.html

24. Command details & Tips
 adb logcat
 adb install/uninstall
 adb reboot/reboot-bootloader
 adb emu
 adb backup/restore
 Joke commands
 Add USB vendor ID
 Restriction of server socket of Android emulator
 Similar restriction in server socket created by
”adb forward” 24

25. adb logcat
 There is ”log:” subcommand in adb server, but
”adb logcat” doesn't use it
 ”adb logcat” executes /system/bin/logcat
remotely
 Tag filtering is done in target side
 Logging in DDMS filtering in host side
 similar to
”adb shell
ANDROID_LOG_TAGS=$ANDORID_LOG_TAGS
logcat args..”
25

26. adb install/uninstall
 adb install
 transfer apk file and then execute
/system/bin/pm at the device
 adb uninstall
 just execute /system/bin/pm remotely

27. adb reboot/reboot-bootloader
 fork&exec /system/bin/vdc to unmount
storage
 wait for the process and then reboot
by system call

28. adb emu
 You can send a single command to emulator
console easily
 send only. can not receive.
 For emulator console,
 http://developer.android.com/guide/developing/devices/emulator.html
 Simple example. ”adb emu window scale 0.5”
after starting emulator
 http://blog.kmckk.com/archives/4091258.html
28

29. adb backup/restore
 New in Android 4.0
 You can backup/restore installed
applications with their saved status.
29

30. Joke commands
 adb hell
 same as ”adb shell” except ”hell” color :)
 Just try.
 adb lolcat
 same as ”adb logcat”
30

31. Add USB Vendor ID
 When connecting USB device, adb checks USB
Vendor ID
 Many USB Vendor IDs are hard coded in adb.
(But not enough)
 To add USB Vendor ID, make
”$HOME/.android/adb_usb.ini” and write one ID
in one line
 See usb_vendors.c
31

32. Restriction of server socket of
Android emulator
Other host Host
Emulator
Adb clients Adb clients
TCP port:5037 Adbd TCP port:5037
TCP
Adb server Adb server
QEMU
All server sockets in Android emulator accepts only from localhost.
If you feel inconvenient in this restriction, apply the patch in next page.
http://blog.kmckk.com/archives/3882865.html 32

33. Patch to allow connecting from
outside (for experiment)
external/qemu
diff --git a/slirp-android/socket.c b/slirp-android/socket.c
index 439590a..ed16d5a 100644
--- a/slirp-android/socket.c
+++ b/slirp-android/socket.c
@@ -650,7 +650,7 @@ solisten(u_int port, u_int32_t laddr, u_int lport, int
flags)
so->so_laddr_ip = laddr; /* Ditto */
so->so_haddr_port = port;
- s = socket_loopback_server( port, SOCKET_STREAM );
+ s = socket_inaddr_any_server( port, SOCKET_STREAM );
if (s < 0)
return NULL;
diff --git a/sockets.c b/sockets.c
index 1063339..55b5d57 100644
--- a/sockets.c
+++ b/sockets.c
@@ -1337,6 +1337,11 @@ socket_in_client( SockAddress* to, SocketType type )
return socket_connect_client( s, to );
}
+int
+socket_inaddr_any_server( int port, SocketType type )
+{
+ return socket_in_server( INADDR_ANY, port, type );
+}
int 33
socket_loopback_server( int port, SocketType type )

34. Similar restriction in server
socket created by ”adb forward”
adb forward tcp:1234 tcp:1234
Other host Host Target device
server socket
port 1234
Transport client socket
client
USB or TCP port 1234
From localhost only
34

35. Patch to allow connecting from
outside (for experiment)
system/core
diff --git a/adb/adb.c b/adb/adb.c
index f5e6e0c..1405e1c 100644
--- a/adb/adb.c
+++ b/adb/adb.c
@@ -481,7 +481,8 @@ int local_name_to_fd(const char *name)
if(!strncmp("tcp:", name, 4)){
int ret;
port = atoi(name + 4);
- ret = socket_loopback_server(port, SOCK_STREAM);
+ ret = socket_inaddr_any_server(port, SOCK_STREAM);
return ret;
}
#ifndef HAVE_WIN32_IPC /* no Unix-domain sockets on Win32 */

36. Advanced Topics
 adb in Android device
 Port adbd to other than Android
36

37. adb in Android device
 Usually, adb is running on the host side,
such as Linux, MacOS and Windows
 In Android 4.0 there is /system/bin/adb in
Android file system
 What for is this?
37

38. Connect its own adbd by adb
 Restart adbd in TCP mode
 Then type ”adb devices”
 It can connect its own adbd by local loop back
Target device
Adb clients But what is
the use case?
TCP port:5038
TCP
Adbd Adb server
http://blog.kmckk.com/archives/4092970.html 38

39. Connect other Android device by
adb on Android
NexusOne
(Android 2.3.6) USB Host
(A connector)
USB device KZM-A9-Dual board
(micro B connector) (Android 4.0.3)
http://blog.kmckk.com/archives/4094716.html
39

40. Connect other Android device by
adb on Android(cont.)
At the serial console on KZM-A9-Dual board
# adb devices
* daemon not running. starting it now on port 5038 *
* daemon started successfully *
List of devices attached
HT015P803242 device
#
It worked!
You can do ”adb shell”, ”adb logcat”, too.
Even you can install application from the board
to NexusOne by ”adb install foo.apk”.
40

41. Port adbd to other than Android
 Quick hack!
 Consider dependency for better porting
ARM Ubuntu 11.10
ARM Ubuntu 11.10
Adbd
Kernel with Android patch
Kernel with Android patch
41

42. Quick hack!
 /sbin/adbd is statically linked executable.
 Just copy this file to ARM Ubuntu 11.10 just for
experiment (using Android patched kernel)
 Somehow, it worked without any recompilation
 sudo chmod 666 /dev/android_adb*
 make symbolic link /bin/sh to /system/bin/sh
 adbd runs in secure mode
 It worked ”adb shell”, ”adb push/pull”
 http://blog.kmckk.com/archives/4093193.html
42

43. Consider dependency for better
porting
 Some service requires other android
commands
 adb install/uninstall, adb bugreport
 framebuffer service invokes /system/bin/screencap
 Adbd uses Android system properties
 At the binary experiment, all property_get returns
default values.
 That's why adbd ran in secure mode.
 Switching adbd mode assumes that init restarts
adbd process
43

44. Q&A
Thank you for listening!
Any comments to blogs are welcome.
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