wagon-ftp sometimes does not build due to socket errors in tests

The wagon-ftp provider build sometimes do not continue due to a SocketException in the unit test. This message is displayed several times:

[ERROR] Exception accepting connection
java.net.SocketException: Socket is closed
at java.net.ServerSocket.accept(ServerSocket.java:417)
at org.apache.avalon.cornerstone.blocks.connection.Connection.run(Connection.java:134)
at org.apache.excalibur.thread.impl.ExecutableRunnable.execute(ExecutableRunnable.java:90)
at org.apache.excalibur.thread.impl.WorkerThread.run(WorkerThread.java:136)

There are times though that the build will succeed so this seems to be an inconsistent occurrence.