Tomcat as Clients communicating with multiple separated Servers via SSL - sockets

Question

Here is the scenario:
I have multiple application servers running locally for now (should be running in different host) --> each is listening on different port (at localhost).
I have a single client application running on Tomcat.
When startup Tomcat, login with different user's details with connect to different (above) servers remotely.
My problem is:
First, I startup Tomcat and logged in as userA, it then connected successfully to serverA(localhost:1000).
Then I logged out.
Logged in again as userB, it did NOT connect to serverB(localhost:1001) as expected; instead, it gave exception
"javax.net.ssl.SSLHandshakeException: Received fatal alert: certificate_unknown"
However, if I restart Tomcat, and login as userB first, it then connects successfully to serverB.
Does anyone know what the problem is?
I really appreciate any suggestion :)
Code for client Tomcat:
SetupClientKeystore();
SetupServerKeystore();
SSLContext context = SetupSSLContext();
SSLSocketFactory socketFactory = sslContext.getSocketFactory();
SSLSocket socket = (SSLSocket) socketFactory.createSocket(hostname, portNo);
GZIPOutputStream gZipOut = new GZIPOutputStream(socket.getOutputStream()); // no trust certificate found throws here
Code for serverA and B:
setupClientKeyStore();
setupServerKeystore();
setupSSLContext();
server = new ServerSocket(portNo);
SSLServerSocketFactory socketFactory = sslContext.getServerSocketFactory();
serverSocket = (SSLServerSocket) socketFactory.createServerSocket(portNo);
serverSocket.setNeedClientAuth(true);
while ( true )
{
Socket client = serverSocket.accept();
inStream = client.getInputStream();
BufferedInputStream bufferedIn = new BufferedInputStream(inStream); //unknown_certificate throws here
//do something here.....
}

Answer 1

"javax.net.ssl.SSLHandshakeException: Received fatal alert:
certificate_unknown"
This usually indicates that the server's certificate is not trusted.
Could it be that when you log-in as userA you load the trusted certificate of serverA and connect, and then when you try to connect to serverB you try to authenticate serverB using the certificate of ServerA (loaded when you logged in as userA)?
As a result the SSL handshake fails.
So when you restart and login as userB the appropriate certificate (i.e. of ServerB) is loaded and the connection is succesfull?
You have no code in your post but if you do it as I say, this explains the exception.