title: SSL HandShake exception
body: <p>I use SSL connection to connect web client to server. It works without any problem for a long time. But from yesterday it gives following error can anyone tell me the reason. </p>
  
  <pre><code>javax.net.ssl.SSLException: Connection has been shutdown: javax.net.ssl.SSLHandshakeException: Received fatal alert: certificate_unknown
          at com.sun.net.ssl.internal.ssl.SSLSocketImpl.checkEOF(SSLSocketImpl.java:1172)
          at com.sun.net.ssl.internal.ssl.AppInputStream.read(AppInputStream.java:65)
          at net.schubart.fixme.internal.MessageInput.readExactly(MessageInput.java:166)
          at net.schubart.fixme.internal.MessageInput.readMessage(MessageInput.java:78)
          at cc.aot.itsWeb.ClientWriterThread.run(ClientWriterThread.java:241)
          at java.lang.Thread.run(Thread.java:619)
  clientWriter.ready
  Caused by: javax.net.ssl.SSLHandshakeException: Received fatal alert: certificate_unknown
          at com.sun.net.ssl.internal.ssl.Alerts.getSSLException(Alerts.java:174)
          at com.sun.net.ssl.internal.ssl.Alerts.getSSLException(Alerts.java:136)
          at com.sun.net.ssl.internal.ssl.SSLSocketImpl.recvAlert(SSLSocketImpl.java:1586)
          at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:865)
          at com.sun.net.ssl.internal.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1029)
          at com.sun.net.ssl.internal.ssl.SSLSocketImpl.writeRecord(SSLSocketImpl.java:621)
          at com.sun.net.ssl.internal.ssl.AppOutputStream.write(AppOutputStream.java:59)
          at java.io.OutputStream.write(OutputStream.java:58)
          at net.schubart.fixme.internal.Message.write(Message.java:267)
          at net.schubart.fixme.internal.MessageOutput.writeMessage(MessageOutput.java:53)
  </code></pre>