Q:

Can’t execute test with more than 2 devices when using Appium grid

Context:
I have been writing automated test scripts with Appium for quite a while and everything works well most of the time, but now I’m trying to execute tests with multiple devices using Appium grid and I am encountering issues when I’m executing the tests with more than 2 devices.
Problem:
Can’t execute test with Appium grid when using more than 2 devices.
I’m almost certain that the issue is with the node configuration, I simply tried to follow examples online, but didn’t find anywhere defined, what is mandatory in the node configs.
My setup is this:
Node config files:
all the devices are physical
LG K11:
    {
    "capabilities":
        [
            {
            "deviceName":"xxxxxxx",
            "version":"7.1.2",
            "platformName":"Android",
            "automationName": "Appium”,
            "udid":"xxxxxxx"
            }
        ],
    "configuration":
        {
            "cleanUpCycle":3000,
            "timeOut":300000,
            "proxy":"org.openqa.grid.selenium.proxy.DefaultRemoteProxy",
            "url":"http://127.0.0.1:4723/wd/hub",
            "host":"127.0.0.1",
            "port": 4723,
            "register": true,
            "registerCycle": 5000,
            "hubPort":4444,
            "hubHost":"127.0.0.1",
            "hubProtocol": "http"
        }
    }

Samsung Tablet S4:
    {
    "capabilities":
        [
            {
            "deviceName":"xxxxxxx",
            "version":"8.1.0",
            "platformName":"Android",
            "automationName": "Appium",
            "udid":"xxxxxxx"
            }
        ],
    "configuration":
        {
            "cleanUpCycle":3000,
            "timeOut":300000,
            "proxy":"org.openqa.grid.selenium.proxy.DefaultRemoteProxy",
            "url":"http://127.0.0.1:4492/wd/hub",
            "host":"127.0.0.1",
            "port":4492,
            "register": true,
            "registerCycle": 5000,
            "hubPort":4444,
            "hubHost":"127.0.0.1",
            "hubProtocol": "http"
        }
    }

Samsung Galaxy S9:
    {
    "capabilities":
        [
            {
            "deviceName":"xxxxxxx",
            "version":"8.0.0",
            "platformName":"Android",
            "automationName": "Appium",
            "udid":"xxxxxxx"
            }
        ],
    "configuration":
        {
            "cleanUpCycle":3000,
            "timeOut":300000,
            "proxy":"org.openqa.grid.selenium.proxy.DefaultRemoteProxy",
            "url":"http://127.0.0.1:8201/wd/hub",
            "host":"127.0.0.1",
            "port":8201,
            "register": true,
            "registerCycle": 5000,
            "hubPort":4444,
            "hubHost":"127.0.0.1",
            "hubProtocol": "http"
        }
    }

I start the nodes by executing the following commands in 4 separate terminal tabs:
1)java -jar selenium-server-standalone-3.141.59.jar -role hub
2)appium -p 4723 --nodeconfig= /LG_K11.json
3)appium -p 4492 --nodeconfig= /Samsung_Tab_S4.json
4)appium -p 8201 --nodeconfig= /Samsung_Galaxy_S9.json
Then in IntelliJ I run this code to initialise the nodes:
I only change the ports, udid and deviceName capabilities and I run the initialisation methods in separate threads and wait for all of them to finish.
initDevice(String udid, int port){
    DesiredCapabilities capabilities = new DesiredCapabilities();
    capabilities.setCapability("platformName", "Android");
    capabilities.setCapability("deviceName",udid );
    capabilities.setCapability("appPackage", “xxxxxxxxx”);
    capabilities.setCapability("appActivity","MainActivity");
    capabilities.setCapability("platformName","Android");
    capabilities.setCapability("udid",udid);
    capabilities.setCapability("noReset", true);

    try {
        String appiumServerURL = String.format("http://127.0.0.1:%d/wd/hub", port);
        driver = new AndroidDriver(new URL(appiumServerURL), desiredCapabilities);
    } catch (MalformedURLException e) {
        e.printStackTrace();
    }
}

And after initialising, when I try to execute any command, such as findElement, I get this crash on one of the devices:
org.openqa.selenium.WebDriverException: An unknown server-side error occurred while processing the command. Original error: Android bootstrap socket crashed: Error: This socket has been ended by the other party
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:17:03'
System info: host: ‘xxxxxx’, ip: ‘xxxxxxxxxx’, os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.14.3', java.version: '1.8.0_191'
Driver info: io.appium.java_client.android.AndroidDriver
Capabilities {appActivity: MainActivity, appPackage: xxxxxxxxxx, databaseEnabled: false, desired: {appActivity: MainActivity, appPackage: xxxxxxxx, deviceName: xxxxxx, noReset: true, platformName: android, udid: xxxxxxxx}, deviceManufacturer: samsung, deviceModel: SM-G960F, deviceName: xxxxxxx, deviceScreenSize: 1440x2960, deviceUDID: xxxxxxx, javascriptEnabled: true, locationContextEnabled: false, networkConnectionEnabled: true, noReset: true, platform: LINUX, platformName: Android, platformVersion: 8.0.0, takesScreenshot: true, udid: xxxxxxxxxx, warnings: {}, webStorageEnabled: false}
Session ID: xxxxxxxx
*** Element info: {Using=xpath, value=//android.widget.ImageView[@content-desc="More options"]}

    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.openqa.selenium.remote.http.W3CHttpResponseCodec.createException(W3CHttpResponseCodec.java:187)
    at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:122)
    at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:49)
    at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:158)
    at io.appium.java_client.remote.AppiumCommandExecutor.execute(AppiumCommandExecutor.java:239)
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:552)
    at io.appium.java_client.DefaultGenericMobileDriver.execute(DefaultGenericMobileDriver.java:42)
    at io.appium.java_client.AppiumDriver.execute(AppiumDriver.java:1)
    at io.appium.java_client.android.AndroidDriver.execute(AndroidDriver.java:1)
    at org.openqa.selenium.remote.RemoteWebDriver.findElement(RemoteWebDriver.java:323)
    at io.appium.java_client.DefaultGenericMobileDriver.findElement(DefaultGenericMobileDriver.java:62)
    at io.appium.java_client.AppiumDriver.findElement(AppiumDriver.java:1)
    at io.appium.java_client.android.AndroidDriver.findElement(AndroidDriver.java:1)
    at org.openqa.selenium.remote.RemoteWebDriver.findElementByXPath(RemoteWebDriver.java:428)
    at io.appium.java_client.DefaultGenericMobileDriver.findElementByXPath(DefaultGenericMobileDriver.java:152)
    at io.appium.java_client.AppiumDriver.findElementByXPath(AppiumDriver.java:1)
    at io.appium.java_client.android.AndroidDriver.findElementByXPath(AndroidDriver.java:1)
    at org.openqa.selenium.By$ByXPath.findElement(By.java:353)
    at org.openqa.selenium.remote.RemoteWebDriver.findElement(RemoteWebDriver.java:315)
    at io.appium.java_client.DefaultGenericMobileDriver.findElement(DefaultGenericMobileDriver.java:58)
    at io.appium.java_client.AppiumDriver.findElement(AppiumDriver.java:1)
    at io.appium.java_client.android.AndroidDriver.findElement(AndroidDriver.java:1)
    at org.openqa.selenium.support.ui.ExpectedConditions$7.apply(ExpectedConditions.java:205)
    at org.openqa.selenium.support.ui.ExpectedConditions$7.apply(ExpectedConditions.java:201)
    at org.openqa.selenium.support.ui.FluentWait.until(FluentWait.java:249)
    at xxxxxxxxx.BaseScreen.waitAndFind(BaseScreen.java:77)
    at xxxxxxxxx.screens.BaseScreen.waitAndFind(BaseScreen.java:73)
    at xxxxxxxxx.screens.MainScreen.getBroadcastOptionsButton(MainScreen.java:23)
    at xxxxxxxxx.tests.PositiveFlows.userClicksBroadcastOptionsMenu(PositiveFlows.java:400)
    at xxxxxxxxx.tests.PositiveFlows.tc5(PositiveFlows.java:316)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

org.openqa.selenium.WebDriverException: An unknown server-side error occurred while processing the command. Original error: Android bootstrap socket crashed: Error: This socket has been ended by the other party
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:17:03'
System info: host: xxxxxxx, ip: xxxxxxxx, os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.14.3', java.version: '1.8.0_191'
Driver info: io.appium.java_client.android.AndroidDriver
Capabilities {appActivity: MainActivity, appPackage: xxxxxxx, databaseEnabled: false, desired: {appActivity: MainActivity, appPackage: xxxxxxx, deviceName: xxxxxxx, noReset: true, platformName: android, udid: xxxxxxx}, deviceManufacturer: samsung, deviceModel: SM-G960F, deviceName: xxxxxxx, deviceScreenSize: 1440x2960, deviceUDID: xxxxxxx, javascriptEnabled: true, locationContextEnabled: false, networkConnectionEnabled: true, noReset: true, platform: LINUX, platformName: Android, platformVersion: 8.0.0, takesScreenshot: true, udid: xxxxxxx, warnings: {}, webStorageEnabled: false}
Session ID: xxxxxxx
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.openqa.selenium.remote.http.W3CHttpResponseCodec.createException(W3CHttpResponseCodec.java:187)
    at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:122)
    at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:49)
    at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:158)
    at io.appium.java_client.remote.AppiumCommandExecutor.execute(AppiumCommandExecutor.java:239)
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:552)
    at io.appium.java_client.DefaultGenericMobileDriver.execute(DefaultGenericMobileDriver.java:46)
    at io.appium.java_client.AppiumDriver.execute(AppiumDriver.java:1)
    at io.appium.java_client.android.AndroidDriver.execute(AndroidDriver.java:1)
    at org.openqa.selenium.remote.RemoteWebDriver.quit(RemoteWebDriver.java:452)
    at xxxxxxx.tests.PositiveFlows.tearDown(PositiveFlows.java:476)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:33)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

A:

Solved it, the problem was that I needed to pass a bootstrap port, because they were conflicting. So added "-bp 1020x" to the commands.
Before:
appium -p 4723 --nodeconfig= /LG_K11.json

After:
appium -p 4723 -bp 10200 --nodeconfig= /LG_K11.json

This link might help for people facing issues in the future: https://dpgraham.github.io/appium-docs/setup/parallel_tests/

