Port attribute in HTTP Cookie

Recently, I have encountered a http session problem in jetty.
I start two Jetty instances on the same machine. These two jetty instances share the same base URL, but port numbers are different.
    http://example.com:8000/
    http://example.com:9000/
When I visit http://example.com:8000/, a cookie (called JSESSIONID) is set by the server automatically.
After that I visit the other URL http://example.com:9000/, the cookie set for http://example.com:8000/ is sent to the server by user agent. The the server gets confused :-(

After debugging it, I found the reason is that the server does NOT include port number in the Set-Cookie header. According to section 3.3.1 in RFC 2965, if the port attribute is missing in the Set-Cookie header, the user agent would react based on following description:

   Port    The default behavior is that a cookie MAY be returned to any
           request-port.

That means if a cookie is set for address A, the cookie also matches those addresses which share all the same URL components with A but port number.

For tomcat, I searched its email list
http://www.google.com/search?hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=cookie+port+site%3Ahttp%3A%2F%2Fmail-archives.apache.org%2Fmod_mbox%2Ftomcat-users%2F&btnG=Search
It seems that port number currently is not supported in cookie management.

Solution
(1) use different domain names which map to the same IP
(2) use different paths.
E.g.
    http://example.com:8000/webapp1
    http://example.com:9000/webapp2