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Re: PHP socket and NAT

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>> NAT typically is used to change IP-addresses (and maybe port).
>> If A and B are in the same LAN I expect they can address each other
>> directly.
>> For example:
>> A IP: 192.168.178.22
>> B IP: 192.168.178.25
>>
>> Once you go outside your LAN, you (might) need NAT.
>>
>> And sockets have little to do with NAT.
>> A IP package arrives at a certain IP on a certain port: If some
>> socket is listening on that port on that machine, the package will
>> be handled by the listening process.
>>
>> NAT itself is performed by routers and such, not by some service
>> listening to a port.
>>
>> SO in short: No you have to care about it.
>>
>> Disclaimer: If you are talking IP6, things are different.
>>
>> Regards,
>> Erwin Moller
>>
>
> An additional example of NAT that makes things clear.
> This is how it was explained to me when I wanted to know about NAT.
>
> Suppose you have 10 computers on your LAN, and 1 internet gateway
> (some ADSL modem for example).
> All you 10 computers can connect to the internet because they use the
> routers IP address as the gateway.
>
> The router has an INTERNAL (LAN-side) IP address.
> Let's say this LAN-IP is 192.168.178.1
>
> The router also has an EXTERNAL (Internet-side) IP address.
> Let's say internet-side IP is 69.147.94.94. (I made the numbers up)
>
> Now, suppose a few people on the LAN are visiting some websites.
> Suppose compA has IP address 192.168.178.22. (On the LAN)
> Suppose compA has IP address 192.168.178.50. (On the LAN)
>
> CompA (192.168.178.22): requests www.google.com
> CompB: (192.168.178.50)requests www.php.net
>
> The router receives these requests from the LAN side, and sends the
> requests to www.google.com and www.php.net.
> The servers from Google and PHP answer the requests, and send them
> back to the router's IP address (being 69.147.94.94).
>
> Now the problem: How should the router handle these answers? Should it
> send them to 192.168.178.22 or 192.168.178.50, or even another IP on
> the LAN?
>
> This is where NAT comes into the picture.
> It works like this:
> 1) Router receives request from 192.168.178.22 (=LAN)for
> www.google.com. 2) Router thinks up some random port that is not is
> use, eg 33000. 3) Router stores this portnumber (33000) in a table
> together with the requesting LAN IP-address (192.168.178.22).
> 4) Router sends the request to www.google.com TOGETHER with the
> instruction to answer on port 33000.
> 5) When Google answers, the router looks up the portnumber, ans sees
> what (internal) IP-address made this request. This way the router can
> see which internal IP-adress made what request because they all get
> random assigned portnumbers.
>
> That is NAT in short.
>
> So I don't expect you have to worry about that in your case.
>

This example clears the air. So the key is the router comes up with random 
port number, and the reply specifies that port number.

Thanks a lot. 

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PHP socket and NAT "SL" <sb5309@hotmail.com> - 2012-02-23 16:58 +0800
  Re: PHP socket and NAT Erwin Moller <erwinmollerusenet@xs4all.nl> - 2012-02-23 11:32 +0100
    Re: PHP socket and NAT Captain Paralytic <paul_lautman@yahoo.com> - 2012-02-23 02:41 -0800
      Re: PHP socket and NAT Erwin Moller <erwinmollerusenet@xs4all.nl> - 2012-02-23 11:53 +0100
    Re: PHP socket and NAT Erwin Moller <erwinmollerusenet@xs4all.nl> - 2012-02-23 11:52 +0100
      Re: PHP socket and NAT "sl@exabyte" <sb5309@hotmail.com> - 2012-02-23 21:04 +0800
        Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-23 13:37 +0000
  Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-23 11:40 +0000
  Re: PHP socket and NAT Jerry Stuckle <jstucklex@attglobal.net> - 2012-02-23 08:00 -0500
    Re: PHP socket and NAT "sl@exabyte" <sb5309@hotmail.com> - 2012-02-23 21:09 +0800
      Re: PHP socket and NAT Captain Paralytic <paul_lautman@yahoo.com> - 2012-02-23 05:19 -0800
        Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-23 13:53 +0000
          Re: PHP socket and NAT Captain Paralytic <paul_lautman@yahoo.com> - 2012-02-23 06:25 -0800
            Re: PHP socket and NAT Michael Fesser <netizen@gmx.de> - 2012-02-23 18:28 +0100
            Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-23 20:42 +0000
          Re: PHP socket and NAT "M. Strobel" <sorry_no_mail_here@nowhere.dee> - 2012-02-24 11:58 +0100
        Re: PHP socket and NAT "SL" <sb5309@hotmail.com> - 2012-02-24 00:03 +0800
          Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-23 20:44 +0000
          Re: PHP socket and NAT "M. Strobel" <sorry_no_mail_here@nowhere.dee> - 2012-02-24 12:07 +0100
            Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-24 13:22 +0000
              Re: PHP socket and NAT Tim Streater <timstreater@greenbee.net> - 2012-02-24 14:20 +0000
                Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-24 15:39 +0000
                Re: PHP socket and NAT Tim Streater <timstreater@greenbee.net> - 2012-02-24 18:53 +0000
                Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-24 21:04 +0000
                Re: PHP socket and NAT Tim Streater <timstreater@greenbee.net> - 2012-02-24 21:41 +0000
                Re: PHP socket and NAT "Peter H. Coffin" <hellsop@ninehells.com> - 2012-02-26 12:50 -0600
      Re: PHP socket and NAT Erwin Moller <erwinmollerusenet@xs4all.nl> - 2012-02-23 14:37 +0100
      Re: PHP socket and NAT The Natural Philosopher <tnp@invalid.invalid> - 2012-02-23 13:50 +0000

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