error connecting to database

folks it was all working fine few day ago.

But now i am getting the following error when trying to connect to my postgres database from the web application.

org.apache.jasper.JasperException: javax.servlet.ServletException: javax.servlet.jsp.JspException: Unable to get connection, DataSource invalid: "org.postgresql.util.PSQLException: Connection refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections."
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:491)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:401)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)


root cause 

javax.servlet.ServletException: javax.servlet.jsp.JspException: Unable to get connection, DataSource invalid: "org.postgresql.util.PSQLException: Connection refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections."
    org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:862)
    org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791)
    org.apache.jsp.jsps.app_005fserver_jsp._jspService(app_005fserver_jsp.java:293)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

and here is the error shown in eclipse console,

javax.servlet.jsp.JspException: Unable to get connection, DataSource invalid: "org.postgresql.util.PSQLException: Connection refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections."
    at org.apache.taglibs.standard.tag.common.sql.QueryTagSupport.getConnection(QueryTagSupport.java:285)
    at org.apache.taglibs.standard.tag.common.sql.QueryTagSupport.doStartTag(QueryTagSu开发者_JAVA百科pport.java:168)
    at org.apache.jsp.jsps.app_005fserver_jsp._jspx_meth_sql_005fquery_005f0(app_005fserver_jsp.java:339)
    at org.apache.jsp.jsps.app_005fserver_jsp._jspService(app_005fserver_jsp.java:139)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Unknown Source)

---

Check with ps aux that Postgres is running:

ps aux|grep postgres

Also check that it is listening:

.oO(~) $ sudo netstat -anp|grep postgres
tcp        0      0 127.0.0.1:5432          0.0.0.0:*               LISTEN      627/postgres        
tcp        0      0 ::1:5432                :::*                    LISTEN      627/postgres        
udp        0      0 ::1:43536               ::1:43536               ESTABLISHED 627/postgres        
unix  2      [ ACC ]     STREAM     LISTENING     1293   627/postgres        /tmp/.s.PGSQL.5432

If not, check your postgresql.conf and set listen to '*' if you need to connect from external. If you're trying from localhost and failing, try using the socket.