This has been added re-try logic in JDK-8085875. Though it reduced frequency but still cannot totally be avoided without isolated test environment.

Test output:
----------System.out:(2/78)----------
Attempting to recreate server socket with port: 43750
Give up after 5 retries
----------System.err:(32/2157)----------
java.net.BindException: Address already in use (Bind failed)
at java.base/java.net.PlainDatagramSocketImpl.bind0(Native Method)
at java.base/java.net.AbstractPlainDatagramSocketImpl.bind(AbstractPlainDatagramSocketImpl.java:130)
at java.base/java.net.DatagramSocket.bind(DatagramSocket.java:394)
at java.base/java.net.DatagramSocket.<init>(DatagramSocket.java:244)
at java.base/java.net.DatagramSocket.<init>(DatagramSocket.java:301)
at java.base/java.net.DatagramSocket.<init>(DatagramSocket.java:273)
at PortUnreachable.recreateServerSocket(PortUnreachable.java:70)
at PortUnreachable.serverSend(PortUnreachable.java:53)
at PortUnreachable.execute(PortUnreachable.java:111)
at PortUnreachable.main(PortUnreachable.java:125)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
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$SameVMRunnable.run(MainActionHelper.java:230)
at java.base/java.lang.Thread.run(Thread.java:844)
java.net.SocketTimeoutException: Receive timed out
at java.base/java.net.PlainDatagramSocketImpl.peekData(Native Method)
at java.base/java.net.DatagramSocket.receive(DatagramSocket.java:745)
at PortUnreachable.execute(PortUnreachable.java:116)
at PortUnreachable.main(PortUnreachable.java:125)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainActionHelper$SameVMRunnable.run(MainActionHelper.java:230)
at java.base/java.lang.Thread.run(Thread.java:844)