URL connection connectiontimeout and readtimeout issues

[selva raja]

Hi all,

I need to know the feature of connectiontimeout setting for URLConnection. Can anyone provide concrete answer for my below questions:

1. When can we set connectiontimeout?
2. If I give some value in milliseconds for connectiontimeout, what will happen while connecting specific URL?
3. If I am unable to read my Inputstream after connection established, can connectiontimeout property take care of that particular connectivity?,else should we set property for readtimeout also?

example code:

HttpURLConnection connection = null;
      OutputStreamWriter wr = null;
      BufferedReader rd  = null;
      StringBuilder sb = null;
      String line = null;
    
      URL serverAddress = null;
    
      try {
          serverAddress = new URL("http://localhost");
          //set up out communications stuff
          connection = null;
        
          //Set up the initial connection
          connection = (HttpURLConnection)serverAddress.openConnection();
          connection.setRequestMethod("GET");
          connection.setDoOutput(true);
          connection.setReadTimeout(10000);
                    
          connection.connect();
        
          //get the output stream writer and write the output to the server
          //not needed in this example
          //wr = new OutputStreamWriter(connection.getOutputStream());
          //wr.write("");
          //wr.flush();
        
          //read the result from the server
          rd  = new BufferedReader(new InputStreamReader(connection.getInputStream()));
          sb = new StringBuilder();
        
          while ((line = rd.readLine()) != null)
          {
              sb.append(line + '\n');
          }
        
          System.out.println(sb.toString());
                    
      } catch (MalformedURLException e) {
          e.printStackTrace();
      } catch (ProtocolException e) {
          e.printStackTrace();
      } catch (IOException e) {
          e.printStackTrace();
      }
      finally
      {
          //close the connection, set all objects to null
          connection.disconnect();
          rd = null;
          sb = null;
          wr = null;
          connection = null;
      }
  }

Thanks,
selva

[Greg Charles]

That's an interesting question. I found the JavaDocs to be a bit unclear on this point, but with a few experiments, I've found that

URL url = new URL("http://somehost.com");
URLConnection con = url.openConnection();

seem to succeed immediately without trying to contact the host. However:

con.connect();

will try to connect to the remote host.

URLConnection has two timeout methods, one for setting the read timeout, and another for setting the connect timeout. So if you set:

con.setConnectTimeout(10000);

and it can't connect within 10 seconds, it will throw a SocketTimeoutException. Try it!

Another option is setting the system properties: sun.net.client.defaultConnectTimeout and sun.net.client.defaultReadTimeout. I think that would work, but you probably have to set them as you start the JVM, i.e., with a -D parameter.