7stud wrote:
[...]
>
> The strange thing is: the hostname and port in the output are not what
> I'm using in my server program:
> ---------
> import socket
>
> s = socket.socket()
>
> print "made changes 2"
>
> host = socket.gethostname() #I'm not connected to the internet when I
> use this line
> print host
>
> port = 1291
> s.bind((host, port))
>
> s.listen(5)
> while("Ctrl-C hasn't been entered"):
> c, addr = s.accept() #blocks and waits for client connection
> print "Got socket connection from", addr
> c.send("Thank you for connecting. Now get lost.")
> c.close()
> ----------
>
> The full output of that program is:
>
> made changes 2
> my-names-computer.local
> Got socket connection from ('127.0.0.1', 49222)
>
> The hostname now appears to be permanently stuck as "127.0.0.1", and
> the port is wrong. That output was so confusing to me, I wasn't even
> sure whether the file I was editing was actually the file that was
> executing, so I printed out "made changes #" at the top of the file to
> make sure the file I was editing was the one that was actually
> executing.
>
> I can't remember exactly what the output was for addr before I started
> messing around with the HOSTNAME in /etc/config, but I'm pretty sure
> addr contained the same hostname as the line above it in the output,
> and the port matched the port in the program.
>
> Any ideas why the hostname and port in the last line of the output are
> not the same as the ones used in the program anymore?
>
Because the client is using what's called an "ephemeral" port - it is
getting an arbitrary port number from the TCP layer, guaranteed to be
unused by any other socket, and using that to connect to your server
socket. Remember a connection has two ends - the details you are
printing out from your server are those of the client endpoint.
If you run several clients simultaneously you will find that each uses a
different port number. That's exactly what's needed to make sure that
the protocol stack can deliver the right information to the right client.
regards
Steve
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