The underlying implementation for the `java.net.Socket` and `java.net.ServerSocket` APIs has been replaced in this release. JEP 353 provides all the details on this change.

Every effort has been made to ensure that the new implementation is compatible with the old implementation but it is possible that there is existing code that depends on unspecified behavior in corner cases where the old and new implementations behave differently. The JDK continues to include the old implementation (known as "PlainSocketImpl" or the "plain" implementation) to allow such code continue to run. The old implementation is selected by running with the system property "`jdk.net.usePlainSockteImpl`" set, or set to the value "`true`", i.e. run with `-Djdk.net.usePlainSocketImpl` or `-Djdk.net.usePlainSocketImpl=true`. The property can also be configured in the JDK network configuration file, located in `${java.home}/conf/net.properties`. The old implementation, and the system property to select the old implementation, will be removed in a future release.