question about EJB

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Nathac - 23 Dec 2006 07:49 GMT

What is the reason for an ejb to communicate with client through random
ports?

Whan a ejb client access the ejb container, i can specify the ip and port
for the ejb container.
However, the server talks me back with random port. Why this is necessary
and don't give any
options to fix the port number?

S

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Alfred - 23 Dec 2006 11:09 GMT

> What is the reason for an ejb to communicate with client through random
> ports?

How do you want to do that with a lot of parallel requests?

Alfred

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Thomas Hawtin - 23 Dec 2006 14:11 GMT

> What is the reason for an ejb to communicate with client through random
> ports?
[quoted text clipped - 4 lines]
> and don't give any
> options to fix the port number?

It's the standard way to make a TCP connection for most protocols.

Each TCP connection is defined by four values:

server IP address, server port number,
client IP address, client port number

There isn't any difference between client and server when things get
going. The server and client IP address will be fixed. The server port
number will be fixed for any 'well known service' (see /etc/services, or
similar for Windows).

That leaves the client port number, which doesn't matter. It just has to
leave the 4-tuple unique for a given connection. As the other three
numbers are fixed, it should vary. Randomness is helpful, but not
essential, to preventing certain kinds of attacks.

Tom Hawtin

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June - 23 Dec 2006 20:12 GMT

I know breif about the stuff.( but not all ^_^; )

What is the normal way to go through the firewall if
no specifica port is used to communicate with others( client or server )

You might say "use web service".

However, if one container ( web container/ejb container)
are in the differnt network ( for example when applying for the DMZ )
how can I call EJB and let it go through the firewall? The current solution
is to limit the ports Application Server( say 5000 ~ 5100 )
and open the range of ports on the firewall.

Let me know if I am doing something wrong.

Thanks for the help.

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josh.s17@gmail.com - 23 Dec 2006 20:50 GMT

Firewalls don't usually care about what port the client uses only the
port that the server uses.

> I know breif about the stuff.( but not all ^_^; )
>
[quoted text clipped - 12 lines]
>
> Thanks for the help.

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Arne Vajhøj - 24 Dec 2006 04:31 GMT

> Firewalls don't usually care about what port the client uses only the
> port that the server uses.

Personal firewalls for home usage maybe.

Corporate firewalls usually also blocks outgoing
traffic.

Arne

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