[dba-Tech] Question about Ports

Stuart McLachlan stuart at lexacorp.com.pg
Thu Apr 23 10:00:23 CDT 2009


Yes

Think of a port as a frequency or channel that the client and  server talk to each other over,

A "listener" application (server)  monitors a specific port for requests.
The "calling" application (client) has to send a properly formatted request to the server using 
the appropriate port.

There is no point in sending a request to a port which is not being monitored.

Ir's not a case of the sender "recognizing" the port, the sender has to know which port to 
"send" the request to.

In your case, you have two separate elements, Apache/Ruby and mySQL.  Changing th 
mySQL port will not have any effect on Apache.

Your client (web browser) sends a request to Apache on Port 80, This is processed by 
Apache/Ruby which needs to get data from mySQL. Ruby will send a request to mySQL on 
another port (default for mySQL is Port 3306).  mySQL will send the result back to Ruby on 
Port 3306 and Ruby/Apache will send the result back to your browser on Port 80.
 

You really don't want to change your HTTP Port to anything other than 80 - that is the 
standard which your web browser will be sending the HTTP requests on.

How about running Apache/Ruby.mySQL in a Virtual machine with a different IP address?


On 23 Apr 2009 at 10:27, Arthur Fuller wrote:

> I don't understand the concept of Ports except in the most basic sense. IIS
> for example "Listens" on Port 80 by default. So if I switch the Port number
> to, say, 8080, do I have to adjust senders to recognize this new port
> assignment?
> 
> My situation is this: I run IIS on port 80 and Reporting Services works
> fine. But then I also do some stuff in Ruby On Rails and its Apache server
> also wants port 80. If I change the port number on one or the other web
> server, do I have to communicate this info to the dependent programs, and if
> so, how?
> 
> I hope I'm making this clear. What I do currently is shut down IIS before
> switching to RoR, and I would much prefer to skip this step so that both
> could run at once without collisions. In the RoR installation, Apache
> listens on port 80. Would I have to inform MySQL to address a new port
> number? I can see in the .conf file that it's easy to change the port
> number. The part of the puzzle that I cannot fathom is how the Sender knows
> what port to send to.
> 
> TIA,
> Arthur
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