LAN programming

[Blade_792]

In my class, at school, we are programming a UDP chat on al lan with a server structure but we have a bit of a problem.

We need a function to have the ip of the client machine and send it without setting it manually, to be more specific if we have 3 client we don't have to initialize a char array with the ip and convert it but have a function that give the ip in char array, string or directly in binary so we don't have to change the code for every client.

Anyone who know how to do this?

 

[jj9987]

I got two ideas off the top of my head

1) Have a server, that tells you about other clients, who have also connected to the server. Just for finding other clients, just like P2P/BitTorrent.

2) Have one client listen and another send a local broadcast message with their IP.

[Blade_792]

44 minutes ago, jj9987 said:

I got two ideas off the top of my head

1) Have a server, that tells you about other clients, who have also connected to the server. Just for finding other clients, just like P2P/BitTorrent.

2) Have one client listen and another send a local broadcast message with their IP.

we have a client list for the broadcast messages but the problem is that we, for this specific project, are using a login system so we have to tell the client ip to the server so it can be putted in the list for the broadcast.

the solution are 2:

1) the server check the ip, thats i don't know if it's possible 'cause USP

2)the client tell the server his ip, we are opting for these but the first option is better beacuse in that case we have to add the function on the server code instead of modify the function that create the buffer to send on the client

 

[bowrilla]

You could broadcast a message and every recipient running the app responds to it by sending the IP. Or every app simply broadcasts the IP to everyone.

[Blade_792]

3 hours ago, bowrilla said:

You could broadcast a message and every recipient running the app responds to it by sending the IP. Or every app simply broadcasts the IP to everyone.

I need the c++ functions to have the ip because for thise prject we don't have to know wich machine will be in the chat and can't set in advance

[mariushm]

If you want to determine the IP addresses , you have Windows API functions for that : 

 

IPv4 only  Windows 2000 and newer : GetAdaptersInfo : https://docs.microsoft.com/en-us/windows/win32/api/iphlpapi/nf-iphlpapi-getadaptersinfo?redirectedfrom=MSDN

 

IPv4 & IPv6 : Windows XP/2003 and newer : GetAdaptersAddresses : https://docs.microsoft.com/en-us/windows/win32/api/iphlpapi/nf-iphlpapi-getadaptersaddresses?redirectedfrom=MSDN

 

It may also help you to read about WinSock 2 API, here's the reference : https://docs.microsoft.com/en-us/windows/win32/winsock/windows-sockets-start-page-2

 

 

[MisterWhite]

My network knowledge is not great but as @bowrilla said you can broadcast a message. Using UDP you can send a message to any local network device.

Some info I found from a quick google search

 

MSDN

Quote

Setting all the bits of an IP address to one, or 255.255.255.255, forms the limited broadcast address. Sending a UDP datagram to this address delivers the message to any host on the local network segment. Because routers never forward messages sent to this address, only hosts on the network segment receive the broadcast message.

 

https://support.biamp.com/Audia-Nexia/Control/TCP_and_UDP_discovery_methods

Quote

UDP stands for User Datagram Protocol and is one of the core protocols of the Internet Protocol (IP) suite. As for the Broadcast term, it describes the process of broadcasting packets to an entire subnet. (e.g: 192.168.1.001 to 192.168.1.254).

 

Now the actual implementation is up to the language you choose and the available tools on it.

[Franck]

As a beginner you should try TCP instead of UDP. You cut the hassle of rearranging the packet on arrival since TCP does it for you. Also this provide a live connection which gives you the ip and all you need to create a collection of connected clients and keep track of them.

[Blade_792]

On 2/8/2021 at 2:33 PM, Franck said:

As a beginner you should try TCP instead of UDP. You cut the hassle of rearranging the packet on arrival since TCP does it for you. Also this provide a live connection which gives you the ip and all you need to create a collection of connected clients and keep track of them.

since it's a school project i can't choose

[Blade_792]

On 2/7/2021 at 12:24 PM, MisterWhite said:

My network knowledge is not great but as @bowrilla said you can broadcast a message. Using UDP you can send a message to any local network device.

Some info I found from a quick google search

 

MSDN

 

https://support.biamp.com/Audia-Nexia/Control/TCP_and_UDP_discovery_methods

 

Now the actual implementation is up to the language you choose and the available tools on it.

my problem is the actual implementation i c/c++