i am getting connection refused error when i run below code . Please help me

Below is my code :

package xyz;
import net.sf.sahi.client.Browser;
import net.sf.sahi.config.Configuration;
public class Testsahi {
public static void main(String[] args) {
String sahiBase = "D:/workingspace/PC_product/sahi"; // where Sahi is unzipped
String userDataDirectory = "D:/workingspace/PC_product/sahi/userdata"; //path to the userdata directory
Configuration.initJava(sahiBase, userDataDirectory);
// Sets up configuration for proxy. Sets Controller to java mode.
String browserType = "firefox";
// Create a browser and open it
Browser browser = new Browser(browserType);
browser.open();
browser.navigateTo("http://www.google.com";
browser.close();
}
}

Error:

Sahi properties file = \workingspace\PC_product\sahi\config\sahi.properties
Sahi user properties file = \workingspace\PC_product\sahi\userdata\config\userdata.properties
java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.<init>(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.http.HttpClient.New(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.URL.openStream(Unknown Source)
at net.sf.sahi.util.Utils.readURL(Utils.java:129)
at net.sf.sahi.util.Utils.readURL(Utils.java:111)
at net.sf.sahi.client.Browser.execCommand(Browser.java:154)
at net.sf.sahi.client.Browser.openURL(Browser.java:266)
at net.sf.sahi.client.Browser.open(Browser.java:241)
at sdis.Testsahi.main(Testsahi.java:25)
java.lang.NullPointerException
at net.sf.sahi.util.Utils.readURL(Utils.java:137)
at net.sf.sahi.util.Utils.readURL(Utils.java:111)
at net.sf.sahi.client.Browser.execCommand(Browser.java:154)
at net.sf.sahi.client.Browser.openURL(Browser.java:266)
at net.sf.sahi.client.Browser.open(Browser.java:241)
at sdis.Testsahi.main(Testsahi.java:25)
Exception in thread "main" java.lang.NullPointerException
at java.lang.String.<init>(Unknown Source)
at net.sf.sahi.client.Browser.execCommand(Browser.java:154)
at net.sf.sahi.client.Browser.openURL(Browser.java:266)
at net.sf.sahi.client.Browser.open(Browser.java:241)
at sdis.Testsahi.main(Testsahi.java:25)