Getting error of Android bootstrap socket crashed: Error: This socket has been ended by the other party

Can anyone help
I am using parallel testing.
With macOS 10.13.6
Appium version 1.8.1

I am using two different ports

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd" > <suite name="Suite" parallel="tests" thread-count="5" verbose="1" > <test name="Oppo"> <parameter name="deviceName_" value="oppo"/> <parameter name="UDID_" value="xyyyyzzz"/> <parameter name="platformVersion_" value="7.1.1"/> <parameter name="URL_" value="0.0.0.0:4725/wd/hub"/> <classes> <class name="forTesting.TestOppoVivo"/> </classes> </test> <test name="Vivo"> <parameter name="deviceName_" value="vivo"/> <parameter name="UDID_" value="abbbbccc"/> <parameter name="platformVersion_" value="8.1.0"/> <parameter name="URL_" value="0.0.0.0:4730/wd/hub"/> <classes> <class name="forTesting.TestOppoVivo"/> </classes> </test> </suite>

I am getting error
[debug] [AndroidBootstrap] Sending command to android: {“cmd”:“shutdown”}
Unhandled rejection Error: Android bootstrap socket crashed: Error: This socket has been ended by the other party
at Socket. (/usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/lib/bootstrap.js:87:21)
at Socket.emit (events.js:182:13)
at Socket.writeAfterFIN [as write] (net.js:404:8)
at /usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/lib/bootstrap.js:112:25
at tryCatcher (/usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/node_modules/bluebird/js/main/util.js:26:23)
at Promise._resolveFromResolver (/usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/node_modules/bluebird/js/main/promise.js:483:31)
at new Promise (/usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/node_modules/bluebird/js/main/promise.js:71:37)
at AndroidBootstrap.sendCommand$ (/usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/lib/bootstrap.js:108:18)
at tryCatch (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:67:40)
at GeneratorFunctionPrototype.invoke [as _invoke] (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:315:22)
at GeneratorFunctionPrototype.prototype.(anonymous function) [as next] (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:100:21)
at invoke (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:136:37)
at enqueueResult (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:185:17)
at new Promise ()
at new F (/usr/local/lib/node_modules/appium/node_modules/core-js/library/modules/$.export.js:30:36)
at AsyncIterator.enqueue (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:184:12)
at AsyncIterator.prototype.(anonymous function) [as next] (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:100:21)
at Object.runtime.async (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:209:12)
at AndroidBootstrap.sendCommand (/usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/build/lib/bootstrap.js:219:34)
at AndroidBootstrap.shutdown$ (/usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/lib/bootstrap.js:163:18)
at tryCatch (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:67:40)
at GeneratorFunctionPrototype.invoke [as _invoke] (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:315:22)
at GeneratorFunctionPrototype.prototype.(anonymous function) [as next] (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:100:21)
at invoke (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:136:37)
at enqueueResult (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:185:17)
at new Promise ()
at new F (/usr/local/lib/node_modules/appium/node_modules/core-js/library/modules/$.export.js:30:36)
at AsyncIterator.enqueue (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:184:12)
at AsyncIterator.prototype.(anonymous function) [as next] (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:100:21)
at Object.runtime.async (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:209:12)
at AndroidBootstrap.shutdown (/usr/local/lib/node_modules/appium/node_modules/appium-android-bootstrap/build/lib/bootstrap.js:306:34)
at AndroidDriver.deleteSession$ (/usr/local/lib/node_modules/appium/node_modules/appium-android-driver/lib/driver.js:373:28)
at tryCatch (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:67:40)
at GeneratorFunctionPrototype.invoke [as _invoke] (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:315:22)
at GeneratorFunctionPrototype.prototype.(anonymous function) [as next] (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:100:21)
at GeneratorFunctionPrototype.invoke (/usr/local/lib/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:136:37)
[debug] [AndroidBootstrap] Emitting alert message…
[debug] [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Emitting system alert message