java.net.BindException during query evaluation

[Billig, Andreas]

Hello team,

we are developing a constraints checker (schema-check under Closed World 
Assumption (OWL, RDFS, etc.)) for a quad store and implement it via SPARQL/HTTP.
We ran into java.net.BindException during query evaluation.

I have isolated the code and made an abstraction. So now with the following code

-----
        for (int i = 0; i < 20000; i++) { // TODO (i:~16300)
            QueryExecution qe =
                
QueryExecutionFactory.sparqlService("http://localhost:3030/Yyy/query";, "select 
* {?x ?y ?z}"); // only two solutions to keep the result set small

            System.out.println(i);

            ResultSet rs = qe.execSelect();

            while (rs.hasNext()) {
                System.out.println(rs.next());
            }

            qe.close();
        }
-----

I got an exception around i > 16000 (so may be some queuing is involved) with 
trace

------
HttpException: java.net.BindException: Address already in use: connect: 
Unexpected error making the query: java.net.BindException: Address already in 
use: connect
    at com.hp.hpl.jena.sparql.engine.http.HttpQuery.rewrap(HttpQuery.java:417)
    at com.hp.hpl.jena.sparql.engine.http.HttpQuery.execGet(HttpQuery.java:358)
    at com.hp.hpl.jena.sparql.engine.http.HttpQuery.exec(HttpQuery.java:295)
    at 
com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP.execResultSetInner(QueryEngineHTTP.java:346)
    at 
com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP.execSelect(QueryEngineHTTP.java:338)
    <own trace items>
    ...
Caused by: java.net.BindException: Address already in use: connect
    at java.net.DualStackPlainSocketImpl.connect0(Native Method)
    at 
java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:79)
    at 
java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
    at 
java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
    at 
java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:579)
    ...
------

Is this a known problem? It would be nice to have some solution because I 
prefer not to go back to embedded TDB, where this error probably does not occur 
(?).

thanks in advance, Andreas