I am creating a signup application with validation and Captcha (using SimpleCaptcha). I am able to deploy my application on localhost and everything works perfectly inclusive of the captcha.

But when deployed the war file to a test server, my captcha is not working, and here s an output from the log file:

org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:111) 
Servlet SimpleCaptchaServlet is currently unavailable

I did register my SimpleCaptchaServlet on the web.xml, and I can locate the class file for that Servlet, but still unable to locate the problem. May I know how can I fix this issue?

Here s the web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
    <servlet-name>SignupProcessServlet</servlet-name>
    <servlet-class>com.example.controller.SignupProcessServlet</servlet-class>
</servlet>
<servlet>
    <servlet-name>SignupSuccessServlet</servlet-name>
    <servlet-class>com.example.view.SignupSuccessServlet</servlet-class>
</servlet>
<servlet>
    <servlet-name>SignupServlet</servlet-name>
    <servlet-class>com.example.view.SignupServlet</servlet-class>
</servlet>
<servlet>
    <servlet-name>SimpleCaptchaServlet</servlet-name>
    <servlet-class>com.example.controller.SimpleCaptchaServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>SignupProcessServlet</servlet-name>
    <url-pattern>/signup_process.do</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>SignupSuccessServlet</servlet-name>
    <url-pattern>/signup_success.view</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>SignupServlet</servlet-name>
    <url-pattern>/signup.view</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>SimpleCaptchaServlet</servlet-name>
    <url-pattern>/captchaImg</url-pattern>
</servlet-mapping>
<session-config>
    <session-timeout>
        30
    </session-timeout>
</session-config>
<welcome-file-list>
    <welcome-file>signup.html</welcome-file>
</welcome-file-list>

Thank you very much.