httpClient connection is in time_wait status in multiple threads code - apache-httpclient-4.x

Question

I need to write a code to send a server request consequently, the request is xml format string. After doing research, I select to use multiple threads and connection pool manager to handle the request and response . I use PoolingHttpClientConnectionManager, httpclient 4.3 version. When I use one thread, the code works, send request and get the response. But when I make it as multiple thread and using single httpclient, the connection seems broken. I use netstat to check and see the TCP status is TIME_WAIT. My code is like:
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
cm.setMaxTotal(50);
cm.setDefaultMaxPerRoute(10);
cm.setMaxPerRoute(new HttpRoute(new HttpHost(ENV_ ABCD)), 20);
CloseableHttpClient httpclient = HttpCleints.custom().setConnectionManager(cm).build();
I use thread pool too, each thread is used to handle one task (runnable). The task includes generating one request, sending the request to the server and getting and processing the response, once this task finish, the thread is put back to the thread pool and the connection is also put back to the connection pool.
All requests are sent to the same server so far.
The runnable task includes following line code:
HttpPost post = new HttpPost(url);
try {
// the request is xml string
post.setEntity(new StringEntity(request));
} catch (UnsupportedEncodingException e1) {
e1.printStackTrace();
}
String responseStr = null;
try {
// the commonHttpClient is same instance of httpclient declared above.
HttpResponse response = commonHttpClient.execute(post);
HttpEntity entity = response.getEntity();
if (entity != null){
responseStr = getString(entity.getContent());
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
I do not get any response. I can see the code is hanging on the line of “commonHttpClient.execute(post);”. From the netstat, it tells the client side is close the connection.
I do not have this problem if there is only one thread. Can anyone tell me what part of my code is wrong. Do I miss any step to configure connection? It is hard to find the example using apache httpclient 4.3.
Thanks