Server Ports

Not certain this is for this group but maybe someone here can help.

The browser on my desktop (client) requests a web page from a server.
The client sends that request from 'any' local port to server port 80.
From what port does the server deliver the data to the clients 'any' port?
Is it from port 80 or does it use another port on the server to send the
data?

Any pointers to articles or such that deal with this appreciated. I have
'googled' but all I can come up with are articles on the protocol.
Thanks,
Seán

ClareOldie

ClareOldie wrote:
> Not certain this is for this group but maybe someone here can help.
>
> The browser on my desktop (client) requests a web page from a server.
> The client sends that request from 'any' local port to server port 80.
> From what port does the server deliver the data to the clients 'any'
> port? Is it from port 80 or does it use another port on the server to
> send the data?
>
> Any pointers to articles or such that deal with this appreciated. I
> have 'googled' but all I can come up with are articles on the
> protocol. Thanks,
> Seán

According to my understanding of the LanSuite Manual the server uses a port
other than port 80 to send the data to the client. Is this true?? Quote
below
Seán

The port above 1023 is the source port; the standard port
is the destination port. The destination machine will return packets using
the original port above 1023 as its destination port. Although this sounds
complicated, the underlying principle is easy to grasp: when a program uses
a port above 1023, replies arrive back at that same port. Here's one last
bit of complexity.
******** Since standard listening ports are for everybody, the
destination machine does not actually use it for data transfer. It only
listens on that port. As soon as a connection is established it hands that
connection to a local port above 1023 and immediately resumes listening for
a new incoming connection request on the standard port. That is how' a web
server can listen for (and handle) thousands of connections from users.

ClareOldie

In article <XYKyb.2890$>,
ClareOldie <> wrote:
>
>
>ClareOldie wrote:
>> Not certain this is for this group but maybe someone here can help.
>>
>> The browser on my desktop (client) requests a web page from a server.
>> The client sends that request from 'any' local port to server port 80.
>> From what port does the server deliver the data to the clients 'any'
>> port? Is it from port 80 or does it use another port on the server to
>> send the data?

Request:

client uses any port -> server port 80


Response:

server port 80 -> port used by client

The tuple (client IP, client port, server IP, server port) uniquely
defines a TCP connection.

Source: the IP RFC or any book on TCP/IP.

Craig

Craig A. Finseth

Craig A. Finseth wrote:
> In article <XYKyb.2890$>,
> ClareOldie <> wrote:
>>
>>
>> ClareOldie wrote:
>>> Not certain this is for this group but maybe someone here can help.
>>>
>>> The browser on my desktop (client) requests a web page from a
>>> server. The client sends that request from 'any' local port to
>>> server port 80. From what port does the server deliver the data to
>>> the clients 'any' port? Is it from port 80 or does it use another
>>> port on the server to send the data?
>
> Request:
>
> client uses any port -> server port 80
>
>
> Response:
>
> server port 80 -> port used by client
>
> The tuple (client IP, client port, server IP, server port) uniquely
> defines a TCP connection.
>
> Source: the IP RFC or any book on TCP/IP.
>
> Craig

Thanks Craig for your reply. Have you any comment on the quotation in my
second post?
I thought it was as you described but this manual has me confused.
Seán

ClareOldie

"ClareOldie" <> wrote in message
newsMGyb.2854$...
> Not certain this is for this group but maybe someone here can help.
>
> The browser on my desktop (client) requests a web page from a server.
> The client sends that request from 'any' local port to server port 80.
> From what port does the server deliver the data to the clients 'any'
port?
> Is it from port 80 or does it use another port on the server to send
the
> data?
>
> Any pointers to articles or such that deal with this appreciated. I
have
> 'googled' but all I can come up with are articles on the protocol.
> Thanks,
> Seán
>
>

The client will initiate the connection from any port above 1024 to the
web server which is listening on port 80.

--
Best regards,
Don Kelloway
Commodon Communications

Visit http://www.commodon.com to learn about the "Threats to Your
Security on the Internet".

Don Kelloway

Don Kelloway wrote:

>>
>>
>
> The client will initiate the connection from any port above 1024 to
> the web server which is listening on port 80.

Yes but does the server send the data to the client from its port 80 or does
it hive off the data send to a port other than 80 and continue listening on
80 as the quote states?

Seán

ClareOldie

For standard port 80 requests, the client will use a port above 1023 and
talk to port 80 on the server. The server will respond back on port 80 to
the port the client used.
1.2.3.4:1024 -> 5.6.7.8:80 (request)
5.6.7.8:80 -> 1.2.3.4:1024 (reply)

What you read in your book can hold true for other applications that use
port mapper. The initial connection is made on a well-known port and then
is moved to a port above 1023. TFTP can work like that as well as many
Unix-based applications. So the manual you read is correct in some
instances. For web-based traffic, the data normally stays on port 80 (for
standard http).

Hope that helps.

Mike


"ClareOldie" <> wrote in message
newsMGyb.2854$...
> Not certain this is for this group but maybe someone here can help.
>
> The browser on my desktop (client) requests a web page from a server.
> The client sends that request from 'any' local port to server port 80.
> From what port does the server deliver the data to the clients 'any' port?
> Is it from port 80 or does it use another port on the server to send the
> data?
>
> Any pointers to articles or such that deal with this appreciated. I have
> 'googled' but all I can come up with are articles on the protocol.
> Thanks,
> Seán
>
>

reshman

"ClareOldie" <> wrote in message
news:%J%yb.2975$...
>
> >
> > The client will initiate the connection from any port above 1024 to
> > the web server which is listening on port 80.
>
> Yes but does the server send the data to the client from its port 80
or does
> it hive off the data send to a port other than 80 and continue
listening on
> 80 as the quote states?
>

The data (or webpage content) is passed to the client from port 80 on
the server and the server will continue to listen on TCP port 80 for any
new incoming connection requests.

--
Best regards,
Don Kelloway
Commodon Communications

Visit http://www.commodon.com to learn about the "Threats to Your
Security on the Internet".

Don Kelloway