Problem when invoking a web service multiple times

I have a java client which invokes an apache axis web service (deployed on an Oracle Application Server on a remote machine) multiple times.

The client distributes the web service invokes among multiple threads, every thing goes well but after an average of 300 web service invokes (among all threads) ab exception is thrown from the client:

java.net.SocketException: Unable to establish connection
at org.apache.axis.AxisFault.makeFault(AxisFault.java:101)
at org.apache.axis.transport.http.HTTPSender.invoke(HTTPSender.java:154)
at org.apache.axis.strategies.InvocationStrategy.visit(InvocationStrategy.java:32)
at org.apache.axis.SimpleChain.doVisiting(SimpleChain.java:11
at org.apache.axis.SimpleChain.invoke(SimpleChain.java:83)
at org.apache.axis.client.AxisClient.invoke(AxisClient.java:165)
at org.apache.axis.client.Call.invokeEngine(Call.java:2784)
at org.apache.axis.client.Call.invoke(Call.java:2767)
at org.apache.axis.client.Call.invoke(Call.java:2443)
at org.apache.axis.client.Call.invoke(Call.java:2366)
at org.apache.axis.client.Call.invoke(Call.java:1812)
at standardwebservice.StandardWebserviceSoapBindingStub.getStandardWebserviceData(StandardWebserviceSoapBindingStub.java:225)
at standardwebservice.StandardWebserviceProxy.getStandardWebserviceData(StandardWebserviceProxy.java:50)
at main.VericalThread.run(VericalThread.java:65)
Caused by: java.net.SocketException: Unable to establish connection
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(Unknown Source)
at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.axis.components.net.DefaultSocketFactory.create(DefaultSocketFactory.java:153)
at org.apache.axis.components.net.DefaultSocketFactory.create(DefaultSocketFactory.java:120)
at org.apache.axis.transport.http.HTTPSender.getSocket(HTTPSender.java:191)
at org.apache.axis.transport.http.HTTPSender.writeToSocket(HTTPSender.java:404)
at org.apache.axis.transport.http.HTTPSender.invoke(HTTPSender.java:13
... 12 more
Thread No. 1 Start for calling 1210ZD106MAT2AAxisFault
faultCode: {http://schemas.xmlsoap.org/soap/envelope/}Server.userException
faultSubcode:
faultString: java.net.SocketException: Unable to establish connection
faultActor:
faultNode:
faultDetail:
{http://xml.apache.org/axis/}stackTrace:java.net.SocketException: Unable to establish connection
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(Unknown Source)
at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.axis.components.net.DefaultSocketFactory.create(DefaultSocketFactory.java:153)
at org.apache.axis.components.net.DefaultSocketFactory.create(DefaultSocketFactory.java:120)
at org.apache.axis.transport.http.HTTPSender.getSocket(HTTPSender.java:191)
at org.apache.axis.transport.http.HTTPSender.writeToSocket(HTTPSender.java:404)
at org.apache.axis.transport.http.HTTPSender.invoke(HTTPSender.java:13
at org.apache.axis.strategies.InvocationStrategy.visit(InvocationStrategy.java:32)
at org.apache.axis.SimpleChain.doVisiting(SimpleChain.java:11
at org.apache.axis.SimpleChain.invoke(SimpleChain.java:83)
at org.apache.axis.client.AxisClient.invoke(AxisClient.java:165)
at org.apache.axis.client.Call.invokeEngine(Call.java:2784)
at org.apache.axis.client.Call.invoke(Call.java:2767)
at org.apache.axis.client.Call.invoke(Call.java:2443)
at org.apache.axis.client.Call.invoke(Call.java:2366)
at org.apache.axis.client.Call.invoke(Call.java:1812)
at standardwebservice.StandardWebserviceSoapBindingStub.getStandardWebserviceData(StandardWebserviceSoapBindingStub.java:225)
at standardwebservice.StandardWebserviceProxy.getStandardWebserviceData(StandardWebserviceProxy.开发者_如何学运维java:50)
at main.VericalThread.run(VericalThread.java:65)

By the way, when I deploy the same web service on an oracle application server on a local machine (in same physical network), every thing goes well and this exception doesn't appear.

By the way, I also tried a JAX-RPC web service and the same exception is thrown.

So please can somebody give me a help.