macaca 服务异常

在使用macaca来做UI遍历测试，一段时间之后就会出现macaca服务连接不上的问题，测试就没法继续执行，得重启手机才行，这样根本就没法用它来做UI测试了
具体错误：
>> uiautomator-client.js:56:14 [master] pid:32664 INSTRUMENTATION_STATUS: id=ActivityManagerService
INSTRUMENTATION_STATUS: Error=Unable to find instrumentation info for: ComponentInfo{com.macaca.android.testing.test/and
roid.support.test.runner.AndroidJUnitRunner}
INSTRUMENTATION_STATUS_CODE: -1

>> uiautomator-client.js:56:14 [master] pid:32664 android.util.AndroidException: INSTRUMENTATION_FAILED: com.macaca.andr
oid.testing.test/android.support.test.runner.AndroidJUnitRunner
at com.android.commands.am.Am.runInstrument(Am.java:1121)
at com.android.commands.am.Am.onRun(Am.java:374)
at com.android.internal.os.BaseCommand.run(BaseCommand.java:47)
at com.android.commands.am.Am.main(Am.java:103)
at com.android.internal.os.RuntimeInit.nativeFinishInit(Native Method)
at com.android.internal.os.RuntimeInit.main(RuntimeInit.java:257)

Error: read ECONNRESET
at exports._errnoException (util.js:1026:11)
at TCP.onread (net.js:569:26)

INSTRUMENTATION_STATUS: stream=
Error in MacacaTestRunner(com.macaca.android.testing.UIAutomatorWD):
java.lang.NullPointerException: Attempt to invoke virtual method 'int com.macaca.android.testing.UIAutomatorWDServer.get
ListeningPort()' on a null object reference
at com.macaca.android.testing.UIAutomatorWD.MacacaTestRunner(UIAutomatorWD.java:25)
at java.lang.reflect.Method.invoke(Native Method)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runners.Suite.runChild(Suite.java:128)
at org.junit.runners.Suite.runChild(Suite.java:27)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
at android.support.test.internal.runner.TestExecutor.execute(TestExecutor.java:59)
at android.support.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:262)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1959)