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Android ADB实现解析
ADB是Android系统提供的调试工具，整个ADB工具由三部分组成：adb client、adb service、adb daemon。
1、ADB client提供HOST端运行的命令2、ADB serviceHOST端上的一个后台进程3、ADB daemomDEVICE端（真实的机器或者模拟器）的守护进程
ADB代码位于/system/core/adb目录下，通过查看Android.mk，可以知道，该目录下的代码生成了两个MODULE，分别是adb和adbd, adb client和adb service都是由adb这个可执行文件实现， adb daemon由adbd实现。adb和adbd的一些源代码文件是用同一个的，编译时通过LOCAL_CFLAGS的参数ADB_HOST来区分，这种你中有我我中有你的关系，对于初次接触的朋友们，多少增加了些困扰。理清了ADB几部分的关系，以及源代码的结构，对ADB的认识已经有一个飞越了。
二、adb_main()函数
其中，adb daemon端代码如下，
一、main函数
adb.c的main函数是adb client、adb service、adb daemon的共同入口，
int main(int argc, char **argv)
{
#if ADB_HOST
adb_sysdeps_init();
adb_trace_init();
D("Handling commandline()\n");
return adb_commandline(argc - 1, argv + 1);
#else
/* If adbd runs inside the emulator this will enable adb tracing via
* adb-debug qemud service in the emulator. */
adb_qemu_trace_init();
if((argc > 1) && (!strcmp(argv[1],"recovery"))) {
adb_device_banner = "recovery";
recovery_mode = 1;
}
start_device_log();
D("Handling main()\n");
return adb_main(0, DEFAULT_ADB_PORT);
#endif
} 根据Android.mk中传入的ADB_HOST确定编译的是adb client\adb service, 或者是adb daemon, ADB_HOST为1时编译adb client\adb service的代码， ADB_HOST为0时编译adb daemon的代码。
以上代码中，adb client\adb service端代码如下,
adb_sysdeps_init();
adb_trace_init();
D("Handling commandline()\n");
return adb_commandline(argc - 1, argv + 1);
1、adb_sysdeps_init(): adb client\adb service适用于linux和windows版本，所以代码中有平台相关的部分。
2、adb_trace_init(): 初始化log输出配置，初始化后在HOST上设置ADB_TRACE这个环境变量，可以控制client\service端的log输出等级，
配置为1或者all的话，将输出所有 的log。
3、adb_commandline(): 关键函数，代码如下。
int adb_commandline(int argc, char **argv)
{
char buf[4096];
int no_daemon = 0;
int is_daemon = 0;
int is_server = 0;
int persist = 0;
int r;
int quote;
transport_type ttype = kTransportAny;
char* serial = NULL;
char* server_port_str = NULL;
/* If defined, this should be an absolute path to
* the directory containing all of the various system images
* for a particular product. If not defined, and the adb
* command requires this information, then the user must
* specify the path using "-p".
*/
gProductOutPath = getenv("ANDROID_PRODUCT_OUT");
if (gProductOutPath == NULL || gProductOutPath[0] == '\0') {
gProductOutPath = NULL;
}
// TODO: also try TARGET_PRODUCT/TARGET_DEVICE as a hint
serial = getenv("ANDROID_SERIAL");
/* Validate and assign the server port */
server_port_str = getenv("ANDROID_ADB_SERVER_PORT");
int server_port = DEFAULT_ADB_PORT;
if (server_port_str && strlen(server_port_str) > 0) {
server_port = (int) strtol(server_port_str, NULL, 0);
if (server_port <= 0 || server_port > 65535) {
fprintf(stderr,
"adb: Env var ANDROID_ADB_SERVER_PORT must be a positive number less than 65535. Got \"%s\"\n",
server_port_str);
return usage();
}
}
/* modifiers and flags */
while(argc > 0) {
if(!strcmp(argv[0],"server")) {
is_server = 1;
} else if(!strcmp(argv[0],"nodaemon")) {
no_daemon = 1;
} else if (!strcmp(argv[0], "fork-server")) {
/* this is a special flag used only when the ADB client launches the ADB Server */
is_daemon = 1;
} else if(!strcmp(argv[0],"persist")) {
persist = 1;
} else if(!strncmp(argv[0], "-p", 2)) {
const char *product = NULL;
if (argv[0][2] == '\0') {
if (argc < 2) return usage();
product = argv[1];
argc--;
argv++;
} else {
product = argv[0] + 2;
}
gProductOutPath = find_product_out_path(product);
if (gProductOutPath == NULL) {
fprintf(stderr, "adb: could not resolve \"-p %s\"\n",
product);
return usage();
}
} else if (argv[0][0]=='-' && argv[0][1]=='s') {
if (isdigit(argv[0][2])) {
serial = argv[0] + 2;
} else {
if(argc < 2 || argv[0][2] != '\0') return usage();
serial = argv[1];
argc--;
argv++;
}
} else if (!strcmp(argv[0],"-d")) {
ttype = kTransportUsb;
} else if (!strcmp(argv[0],"-e")) {
ttype = kTransportLocal;
} else if (!strcmp(argv[0],"-a")) {
gListenAll = 1;
} else if(!strncmp(argv[0], "-H", 2)) {
const char *hostname = NULL;
if (argv[0][2] == '\0') {
if (argc < 2) return usage();
hostname = argv[1];
argc--;
argv++;
} else {
hostname = argv[0] + 2;
}
adb_set_tcp_name(hostname);
} else if(!strncmp(argv[0], "-P", 2)) {
if (argv[0][2] == '\0') {
if (argc < 2) return usage();
server_port_str = argv[1];
argc--;
argv++;
} else {
server_port_str = argv[0] + 2;
}
if (strlen(server_port_str) > 0) {
server_port = (int) strtol(server_port_str, NULL, 0);
if (server_port <= 0 || server_port > 65535) {
fprintf(stderr,
"adb: port number must be a positive number less than 65536. Got \"%s\"\n",
server_port_str);
return usage();
}
} else {
fprintf(stderr,
"adb: port number must be a positive number less than 65536. Got empty string.\n");
return usage();
}
} else {
/* out of recognized modifiers and flags */
break;
}
argc--;
argv++;
}
adb_set_transport(ttype, serial);
adb_set_tcp_specifics(server_port);
if (is_server) {
if (no_daemon || is_daemon) {
r = adb_main(is_daemon, server_port);
} else {
r = launch_server(server_port);
}
if(r) {
fprintf(stderr,"* could not start server *\n");
}
return r;
}
top:
if(argc == 0) {
return usage();
}
/* adb_connect() commands */
if(!strcmp(argv[0], "devices")) {
char *tmp;
char *listopt;
if (argc < 2)
listopt = "";
else if (argc == 2 && !strcmp(argv[1], "-l"))
listopt = argv[1];
else {
fprintf(stderr, "Usage: adb devices [-l]\n");
return 1;
}
snprintf(buf, sizeof buf, "host:%s%s", argv[0], listopt);
tmp = adb_query(buf);
if(tmp) {
printf("List of devices attached \n");
printf("%s\n", tmp);
return 0;
} else {
return 1;
}
}
if(!strcmp(argv[0], "connect")) {
char *tmp;
if (argc != 2) {
fprintf(stderr, "Usage: adb connect <host>[:<port>]\n");
return 1;
}
snprintf(buf, sizeof buf, "host:connect:%s", argv[1]);
tmp = adb_query(buf);
if(tmp) {
printf("%s\n", tmp);
return 0;
} else {
return 1;
}
}
if(!strcmp(argv[0], "disconnect")) {
char *tmp;
if (argc > 2) {
fprintf(stderr, "Usage: adb disconnect [<host>[:<port>]]\n");
return 1;
}
if (argc == 2) {
snprintf(buf, sizeof buf, "host:disconnect:%s", argv[1]);
} else {
snprintf(buf, sizeof buf, "host:disconnect:");
}
tmp = adb_query(buf);
if(tmp) {
printf("%s\n", tmp);
return 0;
} else {
return 1;
}
}
if (!strcmp(argv[0], "emu")) {
return adb_send_emulator_command(argc, argv);
}
if(!strcmp(argv[0], "shell") || !strcmp(argv[0], "hell")) {
int r;
int fd;
char h = (argv[0][0] == 'h');
if (h) {
printf("\x1b[41;33m");
fflush(stdout);
}
if(argc < 2) {
D("starting interactive shell\n");
r = interactive_shell();
if (h) {
printf("\x1b[0m");
fflush(stdout);
}
return r;
}
snprintf(buf, sizeof buf, "shell:%s", argv[1]);
argc -= 2;
argv += 2;
while(argc-- > 0) {
strcat(buf, " ");
/* quote empty strings and strings with spaces */
quote = (**argv == 0 || strchr(*argv, ' '));
if (quote)
strcat(buf, "\"");
strcat(buf, *argv++);
if (quote)
strcat(buf, "\"");
}
for(;;) {
D("interactive shell loop. buff=%s\n", buf);
fd = adb_connect(buf);
if(fd >= 0) {
D("about to read_and_dump(fd=%d)\n", fd);
read_and_dump(fd);
D("read_and_dump() done.\n");
adb_close(fd);
r = 0;
} else {
fprintf(stderr,"error: %s\n", adb_error());
r = -1;
}
if(persist) {
fprintf(stderr,"\n- waiting for device -\n");
adb_sleep_ms(1000);
do_cmd(ttype, serial, "wait-for-device", 0);
} else {
if (h) {
printf("\x1b[0m");
fflush(stdout);
}
D("interactive shell loop. return r=%d\n", r);
return r;
}
}
}
if(!strcmp(argv[0], "kill-server")) {
int fd;
fd = _adb_connect("host:kill");
if(fd == -1) {
fprintf(stderr,"* server not running *\n");
return 1;
}
return 0;
}
if(!strcmp(argv[0], "sideload")) {
if(argc != 2) return usage();
if(adb_download("sideload", argv[1], 1)) {
return 1;
} else {
return 0;
}
}
if(!strcmp(argv[0], "remount") || !strcmp(argv[0], "reboot")
|| !strcmp(argv[0], "reboot-bootloader")
|| !strcmp(argv[0], "tcpip") || !strcmp(argv[0], "usb")
|| !strcmp(argv[0], "root")) {
char command[100];
if (!strcmp(argv[0], "reboot-bootloader"))
snprintf(command, sizeof(command), "reboot:bootloader");
else if (argc > 1)
snprintf(command, sizeof(command), "%s:%s", argv[0], argv[1]);
else
snprintf(command, sizeof(command), "%s:", argv[0]);
int fd = adb_connect(command);
if(fd >= 0) {
read_and_dump(fd);
adb_close(fd);
return 0;
}
fprintf(stderr,"error: %s\n", adb_error());
return 1;
}
if(!strcmp(argv[0], "bugreport")) {
if (argc != 1) return usage();
do_cmd(ttype, serial, "shell", "bugreport", 0);
return 0;
}
/* adb_command() wrapper commands */
if(!strncmp(argv[0], "wait-for-", strlen("wait-for-"))) {
char* service = argv[0];
if (!strncmp(service, "wait-for-device", strlen("wait-for-device"))) {
if (ttype == kTransportUsb) {
service = "wait-for-usb";
} else if (ttype == kTransportLocal) {
service = "wait-for-local";
} else {
service = "wait-for-any";
}
}
format_host_command(buf, sizeof buf, service, ttype, serial);
if (adb_command(buf)) {
D("failure: %s *\n",adb_error());
fprintf(stderr,"error: %s\n", adb_error());
return 1;
}
/* Allow a command to be run after wait-for-device,
* e.g. 'adb wait-for-device shell'.
*/
if(argc > 1) {
argc--;
argv++;
goto top;
}
return 0;
}
if(!strcmp(argv[0], "forward")) {
char host_prefix[64];
char remove = 0;
char remove_all = 0;
char list = 0;
char no_rebind = 0;
// Parse options here.
while (argc > 1 && argv[1][0] == '-') {
if (!strcmp(argv[1], "--list"))
list = 1;
else if (!strcmp(argv[1], "--remove"))
remove = 1;
else if (!strcmp(argv[1], "--remove-all"))
remove_all = 1;
else if (!strcmp(argv[1], "--no-rebind"))
no_rebind = 1;
else {
return usage();
}
argc--;
argv++;
}
// Ensure we can only use one option at a time.
if (list + remove + remove_all + no_rebind > 1) {
return usage();
}
// Determine the <host-prefix> for this command.
if (serial) {
snprintf(host_prefix, sizeof host_prefix, "host-serial:%s",
serial);
} else if (ttype == kTransportUsb) {
snprintf(host_prefix, sizeof host_prefix, "host-usb");
} else if (ttype == kTransportLocal) {
snprintf(host_prefix, sizeof host_prefix, "host-local");
} else {
snprintf(host_prefix, sizeof host_prefix, "host");
}
// Implement forward --list
if (list) {
if (argc != 1)
return usage();
snprintf(buf, sizeof buf, "%s:list-forward", host_prefix);
char* forwards = adb_query(buf);
if (forwards == NULL) {
fprintf(stderr, "error: %s\n", adb_error());
return 1;
}
printf("%s", forwards);
free(forwards);
return 0;
}
// Implement forward --remove-all
else if (remove_all) {
if (argc != 1)
return usage();
snprintf(buf, sizeof buf, "%s:killforward-all", host_prefix);
}
// Implement forward --remove <local>
else if (remove) {
if (argc != 2)
return usage();
snprintf(buf, sizeof buf, "%s:killforward:%s", host_prefix, argv[1]);
}
// Or implement one of:
// forward <local> <remote>
// forward --no-rebind <local> <remote>
else
{
if (argc != 3)
return usage();
const char* command = no_rebind ? "forward:norebind:" : "forward";
snprintf(buf, sizeof buf, "%s:%s:%s;%s", host_prefix, command, argv[1], argv[2]);
}
if(adb_command(buf)) {
fprintf(stderr,"error: %s\n", adb_error());
return 1;
}
return 0;
}
/* do_sync_*() commands */
if(!strcmp(argv[0], "ls")) {
if(argc != 2) return usage();
return do_sync_ls(argv[1]);
}
if(!strcmp(argv[0], "push")) {
if(argc != 3) return usage();
return do_sync_push(argv[1], argv[2], 0 /* no verify APK */);
}
if(!strcmp(argv[0], "pull")) {
if (argc == 2) {
return do_sync_pull(argv[1], ".");
} else if (argc == 3) {
return do_sync_pull(argv[1], argv[2]);
} else {
return usage();
}
}
if(!strcmp(argv[0], "install")) {
if (argc < 2) return usage();
return install_app(ttype, serial, argc, argv);
}
if(!strcmp(argv[0], "uninstall")) {
if (argc < 2) return usage();
return uninstall_app(ttype, serial, argc, argv);
}
if(!strcmp(argv[0], "sync")) {
char *srcarg, *android_srcpath, *data_srcpath;
int listonly = 0;
int ret;
if(argc < 2) {
/* No local path was specified. */
srcarg = NULL;
} else if (argc >= 2 && strcmp(argv[1], "-l") == 0) {
listonly = 1;
if (argc == 3) {
srcarg = argv[2];
} else {
srcarg = NULL;
}
} else if(argc == 2) {
/* A local path or "android"/"data" arg was specified. */
srcarg = argv[1];
} else {
return usage();
}
ret = find_sync_dirs(srcarg, &android_srcpath, &data_srcpath);
if(ret != 0) return usage();
if(android_srcpath != NULL)
ret = do_sync_sync(android_srcpath, "/system", listonly);
if(ret == 0 && data_srcpath != NULL)
ret = do_sync_sync(data_srcpath, "/data", listonly);
free(android_srcpath);
free(data_srcpath);
return ret;
}
/* passthrough commands */
if(!strcmp(argv[0],"get-state") ||
!strcmp(argv[0],"get-serialno") ||
!strcmp(argv[0],"get-devpath"))
{
char *tmp;
format_host_command(buf, sizeof buf, argv[0], ttype, serial);
tmp = adb_query(buf);
if(tmp) {
printf("%s\n", tmp);
return 0;
} else {
return 1;
}
}
/* other commands */
if(!strcmp(argv[0],"status-window")) {
status_window(ttype, serial);
return 0;
}
if(!strcmp(argv[0],"logcat") || !strcmp(argv[0],"lolcat") || !strcmp(argv[0],"longcat")) {
return logcat(ttype, serial, argc, argv);
}
if(!strcmp(argv[0],"ppp")) {
return ppp(argc, argv);
}
if (!strcmp(argv[0], "start-server")) {
return adb_connect("host:start-server");
}
if (!strcmp(argv[0], "backup")) {
return backup(argc, argv);
}
if (!strcmp(argv[0], "restore")) {
return restore(argc, argv);
}
if (!strcmp(argv[0], "jdwp")) {
int fd = adb_connect("jdwp");
if (fd >= 0) {
read_and_dump(fd);
adb_close(fd);
return 0;
} else {
fprintf(stderr, "error: %s\n", adb_error());
return -1;
}
}
/* "adb /?" is a common idiom under Windows */
if(!strcmp(argv[0], "help") || !strcmp(argv[0], "/?")) {
help();
return 0;
}
if(!strcmp(argv[0], "version")) {
version(stdout);
return 0;
}
usage();
return 1;
} adb_commandline解析adb命令，如adb devices, 关于某个命令具体执行过程，后面专门针对某个命令进行解析。
main()中， adbd端代码如下，
/* If adbd runs inside the emulator this will enable adb tracing via
* adb-debug qemud service in the emulator. */
adb_qemu_trace_init();
if((argc > 1) && (!strcmp(argv[1],"recovery"))) {
adb_device_banner = "recovery";
recovery_mode = 1;
}
start_device_log();
D("Handling main()\n");
return adb_main(0, DEFAULT_ADB_PORT); 1、adb_qemu_trace_init()： 建立和模拟器中的adb-debug qemud service的连接。
2、if((argc > 1) && (!strcmp(argv[1],"recovery"))) {
adb_device_banner = "recovery";
recovery_mode = 1;
}
recovery_mode = 1;
}
启动adbd的时候，可以加参数， 例如，在recovery模式中init.rc文件中的adbd service是带recovery参数的，如果带
recovery参数就设置这两个标志，但目前没有看到哪里用到了这两个标志。
3、start_device_log()： 配置adb daemon的log输出， 前面说了adb client和service端的log输出可以通过ADB_TRACE这个环境
变量来控制，adb daemon端的log可以通过persist.adb.trace_mask控制， start_device_log()中判persist.adb.trace_mask
的值，如果有值，就会将log输出到/data/adb/目录下。
4、adb_main()：如下
int adb_main(int is_daemon, int server_port)
{
#if !ADB_HOST
int port;
char value[PROPERTY_VALUE_MAX];
umask(000);
#endif
atexit(adb_cleanup);
#ifdef HAVE_WIN32_PROC
SetConsoleCtrlHandler( ctrlc_handler, TRUE );
#elif defined(HAVE_FORKEXEC)
// No SIGCHLD. Let the service subproc handle its children.
signal(SIGPIPE, SIG_IGN);
#endif
init_transport_registration();
#if ADB_HOST
HOST = 1;
#ifdef WORKAROUND_BUG6558362
if(is_daemon) adb_set_affinity();
#endif
usb_vendors_init();
usb_init();
local_init(DEFAULT_ADB_LOCAL_TRANSPORT_PORT);
adb_auth_init();
char local_name[30];
build_local_name(local_name, sizeof(local_name), server_port);
if(install_listener(local_name, "*smartsocket*", NULL, 0)) {
exit(1);
}
#else
property_get("ro.adb.secure", value, "0");
auth_enabled = !strcmp(value, "1");
if (auth_enabled)
adb_auth_init();
// Our external storage path may be different than apps, since
// we aren't able to bind mount after dropping root.
const char* adb_external_storage = getenv("ADB_EXTERNAL_STORAGE");
if (NULL != adb_external_storage) {
setenv("EXTERNAL_STORAGE", adb_external_storage, 1);
} else {
D("Warning: ADB_EXTERNAL_STORAGE is not set. Leaving EXTERNAL_STORAGE"
" unchanged.\n");
}
/* don't listen on a port (default 5037) if running in secure mode */
/* don't run as root if we are running in secure mode */
if (should_drop_privileges()) {
drop_capabilities_bounding_set_if_needed();
/* add extra groups:
** AID_ADB to access the USB driver
** AID_LOG to read system logs (adb logcat)
** AID_INPUT to diagnose input issues (getevent)
** AID_INET to diagnose network issues (netcfg, ping)
** AID_GRAPHICS to access the frame buffer
** AID_NET_BT and AID_NET_BT_ADMIN to diagnose bluetooth (hcidump)
** AID_SDCARD_R to allow reading from the SD card
** AID_SDCARD_RW to allow writing to the SD card
** AID_MOUNT to allow unmounting the SD card before rebooting
** AID_NET_BW_STATS to read out qtaguid statistics
*/
gid_t groups[] = { AID_ADB, AID_LOG, AID_INPUT, AID_INET, AID_GRAPHICS,
AID_NET_BT, AID_NET_BT_ADMIN, AID_SDCARD_R, AID_SDCARD_RW,
AID_MOUNT, AID_NET_BW_STATS };
if (setgroups(sizeof(groups)/sizeof(groups[0]), groups) != 0) {
exit(1);
}
/* then switch user and group to "shell" */
if (setgid(AID_SHELL) != 0) {
exit(1);
}
if (setuid(AID_SHELL) != 0) {
exit(1);
}
D("Local port disabled\n");
} else {
char local_name[30];
build_local_name(local_name, sizeof(local_name), server_port);
if(install_listener(local_name, "*smartsocket*", NULL, 0)) {
exit(1);
}
}
int usb = 0;
if (access(USB_ADB_PATH, F_OK) == 0 || access(USB_FFS_ADB_EP0, F_OK) == 0) {
// listen on USB
usb_init();
usb = 1;
}
// If one of these properties is set, also listen on that port
// If one of the properties isn't set and we couldn't listen on usb,
// listen on the default port.
property_get("service.adb.tcp.port", value, "");
if (!value[0]) {
property_get("persist.adb.tcp.port", value, "");
}
if (sscanf(value, "%d", &port) == 1 && port > 0) {
printf("using port=%d\n", port);
// listen on TCP port specified by service.adb.tcp.port property
local_init(port);
} else if (!usb) {
// listen on default port
local_init(DEFAULT_ADB_LOCAL_TRANSPORT_PORT);
}
D("adb_main(): pre init_jdwp()\n");
init_jdwp();
D("adb_main(): post init_jdwp()\n");
#endif
if (is_daemon)
{
// inform our parent that we are up and running.
#ifdef HAVE_WIN32_PROC
DWORD count;
WriteFile( GetStdHandle( STD_OUTPUT_HANDLE ), "OK\n", 3, &count, NULL );
#elif defined(HAVE_FORKEXEC)
fprintf(stderr, "OK\n");
#endif
start_logging();
}
D("Event loop starting\n");
fdevent_loop();
usb_cleanup();
return 0;
}二、adb_main()函数
上一节中已经附上adb_main()函数代码， 其中，adb service端的代码如下,
usb_vendors_init();
usb_init();
local_init(DEFAULT_ADB_LOCAL_TRANSPORT_PORT);
adb_auth_init();
char local_name[30];
build_local_name(local_name, sizeof(local_name), server_port);
if(install_listener(local_name, "*smartsocket*", NULL, 0)) {
exit(1);
}
.........
start_logging();
}
D("Event loop starting\n");
fdevent_loop();
usb_cleanup(); 1、usb_vendors_init()： 每个设备产家都会定义一个vender id来标识自己的usb 设备，ADB service端只会连接已知的vender
id，这个函数的作用就是初始化一个vender id的数组，初始化后这个数组中将包含adb代码中内建的一些产家的id以及HOST
端的android配置文件中定义的id。
2、usb_init(): 创建一个线程，线程处理函数device_poll_thread, 进入一个循环，每隔1s执行一次find_usb_device和
kick_disconnected_devices,find_usb_device搜索所有的usb设备，判断vender id是否在上面初始化的列表中，如果是，则
将该usb设备注册到一个handle_list中。调用register_usb_transport基于这个fd 构造一个atransport类型的对象，再基于
这个atransport对象调用register_transport构造一个tmsg类型的对象。
最后，将这个tmsg对象写到transport_registration_send这个fd, 将触发相应的socket监控。kick_disconnected_devices
判断adb设备是否还正常，不正常的话从handle_list中支掉。
3、local_init(): 创建一个线程，尝试连接HOST端5555-5585端口，如果连接成功，则返回一个fd, register_socket_transport
基于这个fd 构造一个atransport类型的对象，再基于这个atransport对象调用register_transport构造一个tmsg类型的
对象。最后，将这个tmsg对象写 transport_registration_send这个fd, 将触发相应的socket监控。
4、install_listener(): 监听"tcp:5037" , adb client与adb service之间通讯用这个端口。
5、start_logging(): 将stdin重写向到/dev/null, 将stdout、stderr重定向/tmp/adb.log, 然后输出"adb starting"到
stderr。
6、fdevent_loop(): 前面通过fdinstall()注册了几个fde, 这里就通过一个无限循环epoll相应的fd, 有相应的事件则调用
fdinstall时注册的处理函数。
7、usb_cleanup()： usb相关的清理工作，对应linux平台的实现目前为空。
其中，adb daemon端代码如下，
property_get("ro.adb.secure", value, "0");
auth_enabled = !strcmp(value, "1");
if (auth_enabled)
adb_auth_init();
// Our external storage path may be different than apps, since
// we aren't able to bind mount after dropping root.
const char* adb_external_storage = getenv("ADB_EXTERNAL_STORAGE");
if (NULL != adb_external_storage) {
setenv("EXTERNAL_STORAGE", adb_external_storage, 1);
} else {
D("Warning: ADB_EXTERNAL_STORAGE is not set. Leaving EXTERNAL_STORAGE"
" unchanged.\n");
}
/* don't listen on a port (default 5037) if running in secure mode */
/* don't run as root if we are running in secure mode */
if (should_drop_privileges()) {
drop_capabilities_bounding_set_if_needed();
/* add extra groups:
** AID_ADB to access the USB driver
** AID_LOG to read system logs (adb logcat)
** AID_INPUT to diagnose input issues (getevent)
** AID_INET to diagnose network issues (netcfg, ping)
** AID_GRAPHICS to access the frame buffer
** AID_NET_BT and AID_NET_BT_ADMIN to diagnose bluetooth (hcidump)
** AID_SDCARD_R to allow reading from the SD card
** AID_SDCARD_RW to allow writing to the SD card
** AID_MOUNT to allow unmounting the SD card before rebooting
** AID_NET_BW_STATS to read out qtaguid statistics
*/
gid_t groups[] = { AID_ADB, AID_LOG, AID_INPUT, AID_INET, AID_GRAPHICS,
AID_NET_BT, AID_NET_BT_ADMIN, AID_SDCARD_R, AID_SDCARD_RW,
AID_MOUNT, AID_NET_BW_STATS };
if (setgroups(sizeof(groups)/sizeof(groups[0]), groups) != 0) {
exit(1);
}
/* then switch user and group to "shell" */
if (setgid(AID_SHELL) != 0) {
exit(1);
}
if (setuid(AID_SHELL) != 0) {
exit(1);
}
D("Local port disabled\n");
} else {
char local_name[30];
build_local_name(local_name, sizeof(local_name), server_port);
if(install_listener(local_name, "*smartsocket*", NULL, 0)) {
exit(1);
}
}
int usb = 0;
if (access(USB_ADB_PATH, F_OK) == 0 || access(USB_FFS_ADB_EP0, F_OK) == 0) {
// listen on USB
usb_init();
usb = 1;
}
// If one of these properties is set, also listen on that port
// If one of the properties isn't set and we couldn't listen on usb,
// listen on the default port.
property_get("service.adb.tcp.port", value, "");
if (!value[0]) {
property_get("persist.adb.tcp.port", value, "");
}
if (sscanf(value, "%d", &port) == 1 && port > 0) {
printf("using port=%d\n", port);
// listen on TCP port specified by service.adb.tcp.port property
local_init(port);
} else if (!usb) {
// listen on default port
local_init(DEFAULT_ADB_LOCAL_TRANSPORT_PORT);
}
D("adb_main(): pre init_jdwp()\n");
init_jdwp();
D("adb_main(): post init_jdwp()\n"); 1、local_init(): adb daemon的这个函数与adb service端的有所不同，adb service端的local_init只在adb service初始化
的时候扫描一下5555-5585端口，而adb daemon端的local_init会在线程中运行一个无限循环，不停尝试连接5555端口或者由
service.adb.tcp.port\persist.adb.tcp.port设置的端口，因为作为daemon随时要准备为他人服务。
2、init_jdwp(): jdwp全称为java debug wire protocol, 每dalvik VM都会创建一个jdwp, 可以建立在adb或者tcp基础上，
与DDMS或debugger进行通信， 这个函数就是初始化了监听socket描述符"\0jdwp-control"动作。
adb daemon其它部分的代码与adb service都比较类似，可能参考adb service部分。
Android ADB实现解析
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