I am trying to use VBNet (MSwinsock)  to communicate via Ethernet with another application running on the same PC !
(The other application can only send and recieve data via Ethernet).

If I install a 2nd network card how should I set up the IP addresses?

I have 2 other PC's to communicate with via Ethernet, can I have 4 seperate network cards within one PC?
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Irwin SantosComputer Integration SpecialistCommented:

(1) you want all 4 machines to communicate with each other and access the Internet


(2) just have each of the machine communicate between each other?

What operating system(s) are you using?

If (1 or 2), then you will want to get at cable/dsl modem 4-port switch solution

IP address are assigned by the router automatically
GlassglimmerAuthor Commented:
Hi !

I have 3 PC's, a master communicating with 2 slaves.

The Master has 2 applications running which need to communicate with each other.

The main application will communicate with the other 2 PC's and the second internal application. The second application can only communicate with the outside world via the network so effectively I will have one port connected to another port within the same PC !

The operating system will be WindowsXP.

Does that make sense !?


On Master Machine.

You give it a name, like "Master".

In your host file, (c:\windows\system32\drivers\etc\hosts) you define your machine like this:      Master

Then, on App 1, you say you want to send data to Master.  The data flows down the stack and eventually does an ARP for Master and consults the host file and sends the data to itself via the loopback address.  App 2 should pick it up and process it.

You could give the Master a real IP also and use your host file to define it        TheMaster         Slave1         Slave 2

Then on your Slave1 and 2 machines, you have a host file there with TheMaster's address as well as the other Slave.

Plug everything into a hub or switch.  You don't need two NICs (or more) on Master - just one NIC will suffice.

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GlassglimmerAuthor Commented:

And vice-versa, App2 will output to Master ?

Does that not mean that both App1 and App2 will receive an echo back of what they have just sent ?

HTH=Hope this Helps.  I am Pseydocyber, at your service <bows> ... ;)

App2 would have the source of the traffic, so would know where to reply to - which I assume would also be the same IP -  I'm not a programmer/developer, but I think it's strange to have two programs on the same machine have to send traffic up and down the stack to communicate to each other ...

I don't know if they would get echo's or whatever - it would depend on how your programs are written and what they're doing.
You might be better served re-asking this question in a programming forum instead of a networking forum.  Not many Network Engineers I know can write code to communicate over a network - we try to stick to the lower layers 1-4 ... what can I say, we're "bottom feeders"  :)
GlassglimmerAuthor Commented:
I am only developing the the master App1 software, App2 is a proprietory price of software which has no DDE,  OLE or other data transfer capabilities unfortunately! It can only communicate via Ethernet.
1. a) if you only need to test both application on one computer then the client will need to connect to the localhost address; its driven by the the ms loopback adapter and is available on most windows boxes:
you will see that address in your hosts file which can be opened with notepad; %windir%\system32\drivers\etc

   b) If you need to specify on the server side of the application the interface to bind too; you need to bind it to

2. find out the ip address of your one computer and try that instead of the localhost address.
(Windows) Strat menu --> run --> cmd --> ipconfig/all

3. you can add the other computer to the network with ethernet in two ways maybe. a) master computer controlling internet connection. b) all computers having direct access to the dedicated hardware router (internet connection) or an internal internet connection built into a computer.

a) Hardware router and computer running software to control / share the internet connection

                                     <ip address provided by isp>
                                          current modem/router

                           / (DNS / Gateway)
                                Internet Connection Sharing Software

                                                8 Port  Switch                 /               /
              Computer 2                                                   Computer 3                 /               /
              Computer 4                                                   Computer 5

b) either, internal internet connection on computer like a modem, or not running internet connection software; all LAN clients default gateways pointing directly towards the hardware router.

                                                8 Port  Switch
                                     <ip address provided by isp>
                                         current modem/router
                           /                 /               /
              Computer 2                                                   Computer 3                 /               /
              Computer 4                                                   Computer 5
           (DNS / Gateway)

*if you are in an Active Directory network, then the Ad LAN Clients will need their dns pointing to a AD DNS server, and the AD dns server will probably forward to the routers dns / isps dns.

** disable all firewalls (except maybe internet connection) for the sake of testing.
Irwin SantosComputer Integration SpecialistCommented: forgot to draw lines and put color in your diagram ;-)
LOL.  agree.  ;)
:) yep, if i coulda drawed the lines, I would of. was even thinking today they need a WMV / GIF upload feature lol. I wrote that network thingy out last night, and then thought it was an overkill for the question. When i saw this one tonight I thought "cool, i can paste that one down" :))  I'm kinda new (been a google client) and from a network support background; it seems to be interfering with my gaming; I better go shoot some people. :)
Irwin SantosComputer Integration SpecialistCommented:
@immediateaction.... well... I've put down my CS hangout over here and do intellectual stuff.....lot better than redundant frags.
GlassglimmerAuthor Commented:
Thanks Chaps!

Im just trying to digest it all !
I don't have time for games - my wife and kids are more than enough to fill my spare time ...
irwinpks, nice intuition; i do play cs (css). and my weapons of choice is an ak, with a deagle by by my side :) i really dig the intellectual side of this place, and you will be seeing me a bit more.

pseudcyber, I am jealous, not at that stage of my life; I could imagine it is very fulfilling.

Glassglimmer, networking can be easy by following some basics, as shown above. I have copied some definitions i used in another post.

IP Address / Subnet Combo.
Notice the IP Address has the same sets as the subnet mask; four sets of numbers. The 255 in the subnet mask represents what part of the ip address is the Network ID, and the 0 represents the Host ID.

Humans remember computer addresses on the internet by domain names. Computers use ip addresses. When you enter a domain name into Internet Explorer for example, your computer will contact a DNS server on the internet and ask "what is the ip address of, the DNS server will respond, you can get to it by going to

The Gateway is used to find ip addresses that are not on your network. So when you enter into Internet Explorer, you receive an ip address from the DNS server, then your computer compare that address to your own and in this case, send the request to be handled by the default Gateway; i.e. NAT usually.
Irwin SantosComputer Integration SpecialistCommented:
@immediateAction...."irwinpks, nice intuition; i do play cs (css). and my weapons of choice is an ak, with a deagle by by my side :) i really dig the intellectual side of this place, and you will be seeing me a bit more."

If I ever get back on... .[PINESMACK]Exhaulted_Ruler...das' me.
cool irwinpks. i play on Australian 40player servers; my alias as of late is Darth Thoth :)))

Irwin SantosComputer Integration SpecialistCommented:
what's the serverIP? I might jump in for a game or 2 or couple hours..
I will need to check tonight, I am currently at work; I do have CSS loaded here but a bit busy. I wont be gaming for at least 8 hours

aolis_nz at hotmail
Irwin SantosComputer Integration SpecialistCommented:
@glassglimmer...did you forget us?

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GlassglimmerAuthor Commented:
Sorry chaps.... The advice you gave was great and sent me down the right path. Thanks !
Irwin SantosComputer Integration SpecialistCommented:
cool. thank you!  but perhaps marking the comment that worked the best would be more appropriate here.
...and perhaps a split ... :)
I am just happy that you solved your problem; well done Glassgimmer!!!

and well done for the awarded points irwinpks :)))  I will take them back off you on Counter strike source one day ;)

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