以下都是ADB连接问题，可以通过尝试如下步骤，由简单度排序
1. 插拔下USB连接线
2. 关闭USB模式再打开
3. 执行以下命令
adb kill-server
adb start-server
4. 效果与3相同
DDMS - Devices - Reset adb
5. 关闭所有PC套件，例如：
杀死 Wandoujia 相关的所有进程，ok
wandoujia_daemon.exe
wandoujia_helper.exe
6. 重启Eclipse
7. 查看有几个ADB进程，全部杀死再重新启动ADB
8. 查看下USB先是否连接电脑与手机
9. 重启手机
10. 关闭占用5037端口软件
11. 更新adb （见问题14）
1. 查看占用端口5037的PID值
netstat -a -n -o |findstr "5037"
输出结果：
TCP 127.0.0.1:5037 0.0.0.0:0 LISTENING 5096
TCP 127.0.0.1:5037 127.0.0.1:51577 ESTABLISHED 5096
TCP 127.0.0.1:51577 127.0.0.1:5037 ESTABLISHED 4324
netstat -a -n -o |findstr "5037"
输出结果：
TCP 127.0.0.1:5037 0.0.0.0:0 LISTENING 5096
TCP 127.0.0.1:5037 127.0.0.1:51577 ESTABLISHED 5096
TCP 127.0.0.1:51577 127.0.0.1:5037 ESTABLISHED 4324
2. 从上面得知PID = 5096占用了5037端口，现在通过PID查看进程名，看到底哪个进程占用此端口
tasklist /v | findstr 5096
输出结果：
tadb.exe 5096 Console 1 4,932 K Unknown ...... 0:00:02 暂缺
网上查询得知tadb.exe是腾讯管家启动的进程
3. 杀死占用5037端口的进程 tadb.exe
taskkill /f -pid 5096
taskkill /im tadb.exe
输出结果
成功: 已终止 PID 为 5096 的进程。
问题1
The connection to adb is down, and a severe error has occured.
You must restart adb and Eclipse.
Please ensure that adb is correctly located at 'adb.exe' and can be executed.
问题2
ADB server didn't ACK
* failed to start daemon *
问题3
Adb failed to restart！ Make sure the plugin is properly configured
问题4
** Adb connection Error:远程主机强迫关闭了一个现有的连接
问题5
java.io.IOException: 您的主机中的软件中止了一个已建立的连接。
at sun.nio.ch.SocketDispatcher.write0(Native Method)
at sun.nio.ch.SocketDispatcher.write(Unknown Source)
at sun.nio.ch.IOUtil.writeFromNativeBuffer(Unknown Source)
at sun.nio.ch.IOUtil.write(Unknown Source)
at sun.nio.ch.SocketChannelImpl.write(Unknown Source)
at com.android.ddmlib.JdwpPacket.writeAndConsume(JdwpPacket.java:213)
at com.android.ddmlib.Client.sendAndConsume(Client.java:575)
at com.android.ddmlib.HandleHeap.sendREAQ(HandleHeap.java:348)
at com.android.ddmlib.Client.requestAllocationStatus(Client.java:421)
at com.android.ddmlib.DeviceMonitor.createClient(DeviceMonitor.java:854)
at com.android.ddmlib.DeviceMonitor.openClient(DeviceMonitor.java:822)
at com.android.ddmlib.DeviceMonitor.processIncomingJdwpData(DeviceMonitor.java:781)
at com.android.ddmlib.DeviceMonitor.deviceClientMonitorLoop(DeviceMonitor.java:649)
at com.android.ddmlib.DeviceMonitor.access$100(DeviceMonitor.java:42)
at com.android.ddmlib.DeviceMonitor$3.run(DeviceMonitor.java:577)
通常是同时打开了两个eclipse,关闭一个即可
问题6
Failed to install .apk on device '': Unable to open sync connection!
java.io.IOException: Unable to open sync connection!
Launch canceled!
问题7
ADB rejected shell command (rm /data/local/.apk): closed
Error during Sync: Unable to open sync connection!
Error during Sync: Unable to open sync connection!
Adb connection Error:远程主机强迫关闭了一个现有的连接。
Connection attempts: 1
Connection attempts: 2
Connection attempts: 3
问题8
Failed to install .apk on device : Too many open files
com.android.ddmlib.SyncException: Too many open files
Launch failed on device:
问题9
Failed to install .apk on device '': closed
com.android.ddmlib.InstallException: closed
Launch failed on device:
问题10
Installation error: INSTALL_FAILED_INSUFFICIENT_STORAGE
Please check logcat output for more details.
Launch failed on device:
问题11
Installation error: INSTALL_FAILED_UPDATE_INCOMPATIBLE
Please check logcat output for more details.
Launch failed on device:
使用PC套件删除，然后安装不行，通过adb uninstall 再次删除，安装ok
问题12
Android Launch!
Connection with adb was interrupted.
0 attempts have been made to reconnect.
You may want to manually restart adb from the Devices view.
问题13
Unexpected error while launching logcat. Try reselecting the device.] closed
com.android.ddmlib.AdbCommandRejectedException: closed
at com.android.ddmlib.AdbHelper.executeRemoteCommand(AdbHelper.java:381)
at com.android.ddmlib.Device.executeShellCommand(Device.java:462)
at com.android.ddmuilib.logcat.LogCatReceiver$1.run(LogCatReceiver.java:109)
at java.lang.Thread.run(Unknown Source)
问题14
adb server is out of date. killing...
* daemon started successfully *
error: device offline
出现问题的版本
D:\>adb version
Android Debug Bridge version 1.0.29
问题出在adb的版本太低，更新ADT后问题解决
D:\>adb version
Android Debug Bridge version 1.0.31