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Re: socket propgramming

hi vibhu,
    correct. you cannot connect to networks between which there are firewalls.
for example, you know that www.redhat.com is at, still you
cannot connect to it only because you will have firewalls both in your side
(your company firewall) and at redhat.
    firewalls basically would look at your IP packets. they would extract
source address, and have certain policies depending upon the destination
addresses. for example, your firewall might have been configured so that all
packets having a destination address, the network part of which is not any
local network should be dropped. an example with numbers: suppose your network
is, you might have a firewall installed at the gate way that
drops all packets whose destination address is for networks other than This effectively blocks you from accessing other networks.
    similarly, firewall could be configured so that they accept only packets
whose source address is some trustable network - for example, "accept all
packets from network,, etc." When this configuration
exists, all packets belonging to networks not in the above list are dropped.
    what you can understand from this is: while you use the socket API to send
and receive packets, your OS network software constructs IP packets with
source and destination address specified by you (in the simplest case). and,
this is not in your control - assuming that you are not using RAW sockets.
finally, the firewalls look into these IP packets, and filter your packets....
and, might not allow you to connect to certain systems.


Vibhu Rishi wrote:

> Correct me if I am worng ..
> your IP address is something like and you want to connect to
> ?
> no problem if you are in the same network - no firewalls in between.
> if you have a firewall/proxy server in between, then I don't know. - any
> one out there who knows how this can be done ?
> vibhu..
> Ramesh wrote:
> > hi all,
> >
> > i want to communicate to a machine in different subnet means how to
> > acheive it with socket porgramming... i did the same thing lihke
> > creatinga socket and establishing a connection with a machine with the
> > local subnet ... but when i wawnt to connect to a valid ip machine or a
> > machine in diffrent subnet.. how to acheive it programmatically.... can
> > anybody help me...
> >
> > ramesh
> >
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