Re: Millions of Threads ?
frankgerlach@gmail.com wrote:
Hello folks,
I am thinking about a telecom application, which would potentially
handle millions of mobile
phones (J2ME) as clients. Of course, I need a server (J2SE), too.
The "easy" implementation uses TCP connections for the client/server
communication. Problem is that there are only 65000 sockets per IP
address of the server. I think I could solve that by configuring
multiple IP addresses per network card.
I think others have addressed the thread issue, I'll tackle your
misconception about IP. You need to understand the difference between
"sockets" which are a software concept and "ports" which are part of the
IP protocol. There is a limit of 65,536 "ports" per IP address. There is
really no limit other than memory, etc. on the number of "sockets". You
do not use a port per connected user. You have a socket connection with
each user, but they would all probably be communicating to a single IP port.
It is no different than a web server. There can be millions of users of
the web server and they are all connected to port 80 on the server. The
server only has to use one port.
You may have gotten confused by Sun itself! For many years, the Java
tutorial contained a totally incorrect and misleading explanation of how
TCP sockets work. It talked about the server switching from the well
known port (e.g. 80 for a web server) to another socket bound to a
different port once the connection was accepted. This is false. Once the
connection is made you move from the server socket that is listening to
new connections to another socket dedicated to that user, but it is
still bound to the same IP port on the server.
Here is a link to their old bogus tutorial page:
<http://web.archive.org/web/20000301031305/http://java.sun.com/docs/books/tutorial/networking/sockets/definition.html>
You can contrast this with the corrected version (which appears to have
only been corrected this year despite years of protests):
<http://java.sun.com/docs/books/tutorial/networking/sockets/definition.html>
--
Dale King