RMI tunneling & J2SE 5 problem

Question

Hi,
I have a problem that just appeared by changing from jRE1.4 to 1.5 on client side
My program uses RMI to load classes from a server. This server is protected by a firewall and the 80 port is not accessible.
With JRE 1.4, the program was connecting to the server "port to port" by TCP, as we can see in this capture :
10.0.0.1 TCP 30000 > 1301 [ACK] Seq=8310 Ack=4199 Win=14868 Len=0
10.0.0.1 TCP 30000 > 1301 [PSH, ACK] Seq=8310 Ack=4199 Win=14868
10.0.0.1 TCP 30000 > 1301 [ACK] Seq=8542 Ack=4199 Win=14868
82.127.XX.XXX TCP 1301 > 30000 [ACK] Seq=4199 Ack=9948 Win=65535
82.127.XX.XXX TCP 1304 > 30000 [SYN] Seq=0 Ack=0 Win=65535 Len=0
10.0.0.1 TCP 30000 > 1301 [ACK] Seq=9948 Ack=4199 Win=14868
With JRE 1.5, the program tries to connect to port 80 :
10.0.0.1 TCP http > 2180 [SYN, ACK] Seq=0 Ack=1 Win=5840 Len=0
82.127.XX.XXX TCP 2180 > http [ACK] Seq=1 Ack=1 Win=65535 Len=0
82.127.XX.XXX HTTP POST /cgi-bin/java-rmi.cgi?forward=1099 HTTP/1.1
82.127.XX.XXX TCP 2178 > 30000 [ACK] Seq=1338 Ack=526 Win=65010
10.0.0.1 TCP [TCP Out-Of-Order] 30000 > 2178 [PSH, ACK] Seq=351
82.127.XX.XXX TCP [TCP Dup ACK 129#1] 2178 > 30000 [ACK]
82.127.XX.XXX HTTP POST /cgi-bin/java-rmi.cgi?forward=1099 HTTP/1.1
10.0.0.1 TCP http > 2180 [ACK] Seq=1 Ack=389 Win=6432 Len=0
10.0.0.1 HTTP HTTP/1.1 404 Not Found (text/html)
...and receives an error, since the port is not accessible.
Error :
java.io.IOException : HTTP request failed
java.io.IOException: HTTP request failed
at sun.rmi.transport.proxy.HttpSendSocket.readNotify(Unknown Source)
at sun.rmi.transport.proxy.HttpSendInputStream.read(Unknown Source)
at java.io.BufferedInputStream.fill(Unknown Source)
at java.io.BufferedInputStream.read(Unknown Source)
at java.io.DataInputStream.readByte(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at java.rmi.Naming.lookup(Unknown Source)
at com.swingws.biweb.tools.tunneling.b.<init>(Unknown Source)
at com.swingws.biweb.tools.tunneling.b.a(Unknown Source)
at com.swingws.biweb.seriallink.LsServerSelectApplet.init(Unknown Source)
     at sun.applet.AppletPanel.run(Unknown Source)
     at java.lang.Thread.run(Unknown Source)
Do you know why the behaviour of my program changed between the 2 JREs ?

Answer 1

While Debugging, I found why it goes on HTTP connection :
I reused the servlet code from the servletHandler Example.
It is said that :
When an RMI client initiates contact with a remote server,
* it attempts to establish a connection using each of the following
* protocols in turn, until one succeeds:
* 1. Direct TCP connection.
* 2. Direct HTTP connection.
* 3. Proxy connection (SOCKS or HTTP).
* 4. Connection on port 80 over HTTP to a CGI script.
* 5. Proxy HTTP connection to CGI script on port 80.
So, we can think the TCP connection doesn't work, that's why it goes through HTTP.
Then my new question is :
Why the server accepts TCP connections from clients with JRE1.4 and older but not for clients with JRE1.5 ?