Strange multiThreading behaviour for http client

Question

Hi
I am writting an app which Posts data to two separate URL's. Since I didn't want one posting method to be held up by the other one I put each Posting method into its own thread. Each Thread repeatedly creates an HttpClient and posts away data to its respective URL. However I can see that the threads are waiting for eachother! ie: Thread2 won't post its data untill Thread1 receives its http response.
Why could this be ? I am not sharing any objects between the two threads. I even tried implementing the one thread with java.net and the other one with apache.commons.httpclient. Is it physically impossible to send two http requests similtaneously?
Thanks
Aharon

Answer 1

Okay heres the code, I tried to cut out some details but its still quite long winded
I hope the problem is as simple as mistakenly using run() instead of start() ;)
public class test
     * @param args
     public static void main(String[] args)
          FlightTimeManager ftmnew = new FlightTimeManager();
          FlightTracker ft =new FlightTracker();
public class FlightTracker extends Thread
     private final int REFRESH_RATE = 100;
     private boolean finish;
     private long lastId;
     public FlightTracker()
          this.finish = false;
          this.lastId = 0;
          start();
     public void stopTracker()
          this.finish = true;
     public void run()
          while (!finish)
               processFlightList();
               try {
                    Thread.sleep(REFRESH_RATE);
               } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
     private void processFlightList()
          ServerCon serverCon = new ServerCon();
          Vector<String> vec = serverCon.receiveFlightList(this.lastId,20);
          String outputStr = "";
          if (vec != null)
               serverCon = new ServerCon();
               serverCon.updateFlights(vec);
public class ServerCon
     public ServerCon()
     public Vector<String> receiveFlightList(long id,int amount)
          HttpLink httpLink = new HttpLink();
          Vector<String> vec = null;
          String url = "my website url";
          String postStr = "my post parameteres";
          int error = httpLink.converseWithServer(url, postStr,true);
          if (error == HttpLink.OK)
               String flightStr = httpLink.getResponse();
               if (flightStr != null && !flightStr.equals("0"))
                    Scanner scanner = new Scanner(flightStr);
                    vec = new Vector<String>();
                    scanner.useDelimiter(",");
                    while (scanner.hasNext())
                         vec.add(scanner.next());                         
          return vec;
     public boolean updateFlights(Vector<String> flightLocationList)
          HttpLink httpLink = new HttpLink();
          boolean success = false;
          String postStr = "my post parameteres";
          int error = 0;
          String url = "my website url";
          error = httpLink.converseWithServer(url, postStr, false);
          if (error == HttpLink.OK)
               success = true;
          return success;
public class HttpLink
     public static final int OK = 0;
     public static final int ENCODING_EXCEPTION = 1;
     public static final int MALFORMED_URL_EXCEPTION = 2;
     public static final int IO_EXCEPTION = 3;
     private String responseString;
     public HttpLink()
          this.responseString = null;
     public int converseWithServer(String urlStr,String sendStr,boolean waitforResponse)
          int error = OK;
          try
               URL url = new URL(urlStr);
               URLConnection connection = url.openConnection();
               connection.setDoOutput(true);
               OutputStreamWriter out = new OutputStreamWriter(
          connection.getOutputStream());
               out.write(sendStr);
               out.close();
               BufferedReader in = new BufferedReader(
                         new InputStreamReader(
                         connection.getInputStream()));
               if (waitforResponse)
                    boolean receivedInfo = false;
                    String response;     
                    while ((response = in.readLine()) != null)
                         this.responseString = new String(response);
                         receivedInfo = true;
                    if(!receivedInfo)
                         this.responseString = null;
               in.close();
          catch (UnsupportedEncodingException e)
               error = ENCODING_EXCEPTION;
               e.printStackTrace();
               this.responseString = e.getMessage();
          catch (MalformedURLException e)
               error = MALFORMED_URL_EXCEPTION;
               e.printStackTrace();
               this.responseString = e.getMessage();
          catch (IOException e)
               error = IO_EXCEPTION;
               e.printStackTrace();
               this.responseString = e.getMessage();
          return error;
     public String getResponse()
          String response = null;
          if (this.responseString != null)
               response = new String(this.responseString);
               //this.responseString = null;
          return response;
public class FlightTimeManager extends Thread
     private final int REFRESH_RATE = 10000;
     private boolean finish;
     public FlightTimeManager()
          this.finish = false;
          start();
     public void stopManager()
          this.finish = true;
     public void run()
          while (!finish)
               postData();
               try {
                    Thread.sleep(REFRESH_RATE);
               } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
     public void postData()
          String outputStr = "";
          HttpClient httpClient = new HttpClient();
          String url = "my website url";
          PostMethod meth = new PostMethod(url);
          meth.addParameter(some parameter);
          try
               httpClient.executeMethod(meth);
          catch (HttpException e)
               e.printStackTrace();
          catch (IOException e)
               e.printStackTrace();
}