Very odd socket behavior in Java; don't always close ports?

During the development of a significantly large project, we accumulated a lot of unit tests. Many of these tests start servers, connect to these servers, and close servers and clients, usually in the same process.

However, these tests randomly fail with “Failed to bind the address 127.0.0.1:(port". "When the test is restarted, the error usually disappears.

Now we thought it was a problem with our tests, but we decided to write a little test in Clojure, which I will post below (and a comment for people without Clojure).

(ns test
  (:import [java.net Socket ServerSocket]))

(dotimes [n 10000] ; Run the test ten thousand times
  (let [server (ServerSocket. 10000) ; Start a server on port 10000
        client (Socket. "localhost" 10000) ; Start a client on port 10000
        p (.getLocalPort client)] ; Get the local port of the client
    (.close client) ; Close the client
    (.close server) ; Close the server
    (println "n = " n) ; Debug
    (println "p = " p) ; Debug
    (println "client = " client) ; Debug
    (println "server = " server) ; Debug
    (let [server (ServerSocket. p)] ; Start a server on the local port of the client we just closed
      (.close server) ; Close the server
      (println "client = " client) ; Debug
      (println "server = " server) ; Debug
    ))
  )

The exception appears randomly in the line where we start the second server. It seems that Java is holding onto the local port, even if the client on that port is already closed.

, : Java, ?

. - socketAddr true. , , .

(ns test
  (:import [java.net Socket ServerSocket InetSocketAddress]))

(dotimes [n 10000] ; Run the test ten thousand times
  (let [server (ServerSocket. )] ; Create a server socket
    (. server (setReuseAddress true)) ; Set the socket to reuse address
    (. server (bind (InetSocketAddress. 10000))) ; Bind the socket
    (let  [client (Socket. "localhost" 10000) ; Start a client on port 10000
           p (.getLocalPort client)] ; Get the client local port
      (.close client) ; Close the client
      (.close server) ; Close the server
;      (. Thread (sleep 1000)) ; A sleep for testing
      (println "n = " n) ; Debug
      (println "p = " p) ; Debug
      (println "client = " client) ; Debug
      (println "server = " server) ; Debug
      (let [server (ServerSocket. )] ; Create a server socket
        (. server (setReuseAddress true)) ; Set the socket to reuse address
        (. server (bind (InetSocketAddress. p))) ; Bind the socket to the local port of the client we just had
        (.close server) ; Close the server
        (println "client = " client) ; Debug
        (println "server = " server) ; Debug
      )))
  )

, 10 100 . , 1000 ( ) .

2. - SO_LINGER, ServerSockets. - ?

EDIT 3. , SO_LINGER . ?

. , 10 000 . , , .