com/sun/jdi/BadHandshakeTest.java failed with "ConnectException: Connection refused: connect"

The following test failed in the JDK16 CI:

com/sun/jdi/BadHandshakeTest.java

Here's a snippet from the log file:

----------System.out:(10/2384)*----------
Starting debuggee...
Command line: [c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+12-478\\windows-x64-debug.jdk\\jdk-16\\fastdebug\\bin\\java.exe -cp T:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\classes\\6\\com\\sun\\jdi\\BadHandshakeTest.d;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+12-478\\src.full\\open\\test\\jdk\\com\\sun\\jdi;T:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\classes\\6\\test\\lib;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\5.1\\b01\\bundles\\jtreg_bin-5.1.zip\\jtreg\\lib\\javatest.jar;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\5.1\\b01\\bundles\\jtreg_bin-5.1.zip\\jtreg\\lib\\jtreg.jar;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\5.1\\b01\\bundles\\jtreg_bin-5.1.zip\\jtreg\\lib\\junit.jar;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\5.1\\b01\\bundles\\jtreg_bin-5.1.zip\\jtreg\\lib\\testng.jar -Xmx512m -XX:MaxRAMPercentage=3 -Djava.io.tmpdir=t:/testoutput/test-support/jtreg_open_test_jdk_jdk_jdi/tmp -ea -esa -XX:+CreateCoredumpOnCrash -XX:+UseZGC -agentlib:jdwp=transport=dt_socket,server=y,suspend=y Exit0 ]
[debuggee]:c:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+12-478\\windows-x64-debug.jdk\\jdk-16\\fastdebug\\bin\\java.exe -cp T:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\classes\\6\\com\\sun\\jdi\\BadHandshakeTest.d;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jdk-16+12-478\\src.full\\open\\test\\jdk\\com\\sun\\jdi;T:\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_jdi\\classes\\6\\test\\lib;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\5.1\\b01\\bundles\\jtreg_bin-5.1.zip\\jtreg\\lib\\javatest.jar;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\5.1\\b01\\bundles\\jtreg_bin-5.1.zip\\jtreg\\lib\\jtreg.jar;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\5.1\\b01\\bundles\\jtreg_bin-5.1.zip\\jtreg\\lib\\junit.jar;C:\\ade\\mesos\\work_dir\\jib-master\\install\\jtreg\\5.1\\b01\\bundles\\jtreg_bin-5.1.zip\\jtreg\\lib\\testng.jar -Xmx512m -XX:MaxRAMPercentage=3 -Djava.io.tmpdir=t:/testoutput/test-support/jtreg_open_test_jdk_jdk_jdi/tmp -ea -esa -XX:+CreateCoredumpOnCrash -XX:+UseZGC -agentlib:jdwp=transport=dt_socket,server=y,suspend=y Exit0
[debuggee] Listening for transport dt_socket at address: 43605
Debuggee started.
Debuggee port: 43605
testcase 1...
testcase 2...
retry: 0
cleaning...
----------System.err:(21/1383)----------
java.net.ConnectException: Connection refused: connect
at java.base/sun.nio.ch.Net.connect0(Native Method)
at java.base/sun.nio.ch.Net.connect(Net.java:574)
at java.base/sun.nio.ch.Net.connect(Net.java:563)
at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588)
at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:333)
at java.base/java.net.Socket.connect(Socket.java:648)
at jdk.jdi/com.sun.tools.jdi.SocketTransportService.attach(SocketTransportService.java:261)
at jdk.jdi/com.sun.tools.jdi.GenericAttachingConnector.attach(GenericAttachingConnector.java:119)
at jdk.jdi/com.sun.tools.jdi.SocketAttachingConnector.attach(SocketAttachingConnector.java:83)
at BadHandshakeTest.main(BadHandshakeTest.java:122)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:298)
at java.base/java.lang.Thread.run(Thread.java:832)

JavaTest Message: Test threw exception: java.net.ConnectException
JavaTest Message: shutting down test

result: Failed. Execution failed: `main' threw exception: java.net.ConnectException: Connection refused: connect


test result: Failed. Execution failed: `main' threw exception: java.net.ConnectException: Connection refused: connect


Mach5 reports this test duration as 4 seconds which is
really fast for this type of failure mode. That tends to
indicate that the port this test was attempting to connect
to was occupied by some other process.